Heat pumps are obviously great in many ways. But fitting one is a big deal - they are quite expensive, they take a lot of work to fit, really require extensive additional insulation, and there are all sorts of caveats to them that mean they aren't a straightforward replacement for a boiler.
So i'm slightly mystified that we basically don't hear anything about fitting drainwater heat recovery [1], in which the lukewarm drain water from your shower is used to pre-warm the incoming cold water. It's extremely simple, pretty cheap, simple to fit, and can recover ~50% of the waste heat, of something which is tens of percent of the energy consumption of a household.
By all means, get a heat pump. But get a heat exchanger on your shower first!
> But fitting one is a big deal - they are quite expensive, they take a lot of work to fit, really require extensive additional insulation
I think this somewhat overblows the complexity of a heat pump.
They are simply Air conditioners that can be ran in reverse. One valve is the difference between a heat pump and AC. Why they are so expensive is really just price gouging because they aren't as common.
If you are in a home with forced air AC then installing a heatpump system couldn't be simpler and should be something you consider when updating your AC system. It's really just a matter of updating the compressor and maybe adding some smarts to avoid condensation. In fact, it's shocking to me that AC -> heatpump conversion kits haven't hit the market.
> So i'm slightly mystified that we basically don't hear anything about fitting drainwater heat recovery [1], in which the lukewarm drain water from your shower is used to pre-warm the incoming cold water. It's extremely simple, pretty cheap, simple to fit, and can recover ~50% of the waste heat, of something which is tens of percent of the energy consumption of a household.
Really interesting idea, but I assume you have to rip up the shower to accomplish this right? Also, I'm guessing clogged wastewater piping might be an issue right? That said, that'd be easily overcome by just running the lines side by side with maybe a simple copper connector for heat exchange.
What is mystifying to me is why governments allow air conditioners without that reversing valve to be installed. A simple change, and the more people installing a heat pump the cheaper those valves get.
I regret getting just an AC a while ago. I could have gotten a heat pump and used it for most of the heating. Even if I didn't get heat pump installed, one that could have been converted to heat pump without complete replacement would been nice.
Agree with your take. Recently helped install a heat pump at a single-family home (rental property) in the SF Bay Area. Actually, they aren't that much more expensive than AC's (mine cost about $9k for everything, but again, I did 35% of the work myself for a ducted 3 ton heat pump). And yeah, the installation is almost exactly the same as what you'd do for an AC.
And, you don't need to add insulation, but we did (to the crawlspace), costing about $2.5k
And, it's been running for about 3 months, and saved about ~$175/month in heating. wow. It'll pay for itself in about 7-8 years.
How are heat pumps typically installed? Are they integrated into the radiator/hot water system? Or is some sort of forced air system setup installed?
I'd assume a mini split setup wouldn't be too uncommon. (Probably the cheapest route for most homes in the UK).
In the US the vast majority of homes and apartments are setup with forced air heating and cooling which really simplifies transition. I'd assume the UKs setup where everyone uses heated water to heat homes would make transition more expensive and costly.
Heat pumps here heat water. In a new build with a heat pump from the start, or a big refurb, the hot water is used for underfloor heating. In a smaller refurb, or where that's not possible, it's used in radiators, although I think you typically fit special radiators and bigger pipes which can work at a lower temperature.
Some new builds have mechanical ventilation heat recovery, which is a ventilation system with a heat exchanger. But I don't hear much about air to air heat pumps.
It's very possible I'm wrong in my perceptions here!
some air-water heat pumps _can_ run in cooling mode, but speaking to a heating engineer the other week he recommended not doing this for exactly this reason.
You're right; 80% of US homes are single-family with forced air and ducts. Most heat pumps are swap-in replacements for these systems. One central air handler is connected to ductwork and vents to distribute the heat and cooling—one outdoor unit, with refrigerant lines connecting the indoor and outdoor units.
Europe has more hydronic/radiator mono-block heat pumps, with no refrigerant work needed in the field, which makes them easier to retrofit, assuming all the other plumbing is in place. Refrigerant work requires more training due to the high pressure and the potential for the high-GWP refrigerant.
This sounds like an American viewpoint. In Australia, New Zealand and much of Europe they are pretty cheap to install, and rarely require additional insulation.
It may be that they're relatively new to your area, so the demand is outstripping supply of installers who have been doing this for 30+ years and as such are charging to that effect.
> Information obtained from the US Census Bureau’s Survey of Construction (SOC) and tabulated by NAHB, shows that the rising trend of single-story homes reversed in 2021. The share of single-story homes decreased in 2021 and the share of two or more stories homes started was greater than one story homes. This is in line with recent NAHB analysis of new single-family home size trends.
Speaking of heat pumps and water heat, I installed both a heat pump and hybrid water heater to save on electricity. The water heater doesn't seem to have made much of a difference in my electrical bill, my guess is the problem is peak demand so I should have gotten a much bigger tank than before. Ambient garage temperature may also be an issue but it exhausts outside and the garage is insulated so it generally stays above 55 degrees.
they also aren't very hot and wont work in northern cities, but people will install them there anyway. "boiler" - is that jargon for multiple kinds of heating units or actually just boilers?
Heat pumps work down to -25C. Cold climates get colder than that. Sure most cold climates are typically above that, but it only takes one night every 10 years to hit those temperatures and a heat pump alone does not work. You need a backup. Of cousre once we have a backup we can ask if it is cost effect - heat pumps get less efficient as temperatures go down - when you need the most heat, so it may be most cost effective to install a heat pump that doesn't even work to that cold (perhaps it does but is under sized?) and just use backup heat when it is cold.
One night where the outside temperature gets below -25C is not a serious problem. If you had the heat pump keeping your house at a comfortable temperature the day before, you aren't going to die of hypothermia or have pipes freeze overnight. You'll just wake up to a house that's chilly inside and takes most of the day to get back up to where you want it.
Sustained cold spells are where you need an alternative heat source.
I presume you’re talking about air source heat pumps here. Some will go down that far, but it’s not common. If installed in a location where winters will routinely see temperatures below -10/15 degrees C, it’s going to be far more efficient to do a ground source heat pump, ideally with a deep bore hole where you can get a heat source that is continually 10-20 degrees C
As CP says, you design your system for the conditions 99% of the time, because designing for that last 1% leads to a terrible cost benefit calculation. Same reason you don’t daily drive an armored personnel carrier with a 300-gallon gas tank.
Boilers in the UK are usually mounted on the inside of an exterior wall to provide for venting exhaust gases outside. They may provide hot water on-demand without a tank (combi boiler) or fill a hot water cylinder on a schedule (system boiler) depending on type. Heating is typically provided by the boiler pumping hot water through a circuit of wall-mounted radiators regulated by TRVs (Thermostatic Radiator Valves).
Boilers are definitely much more common in the UK than US. I believe New England is one of the few areas of the US that has a relatively high percentage of homes with hydronic+boiler heating setups. In most other parts of the U.S., many people probably have no idea what a boiler even is.
Heat pumps _are_ amazing! The power of physics at play: spend 1 unit of energy to gain 4.
Some naysayers will say that it doesn't work the 3 days of the year where it's -15°C outside, without talking about the other 100+ days where it's not that cold and where the heat pump is amazing.
Disclaimer: I self installed one for my house (13kWth) and I'm very glad I did
So, i have a house in Haliburton Ontario. Historically we drop a cool $3k a year on propane.
Last year we installed a Mitsubishi hyper heat ductless system.
We used zero gas this year. Read it again, zero.
It’s lakefront, very remote, and the largest electricity bill i got was around $450 for a month and then they dropped back to something more like $250. The savings are huge, I’m no longer stressed about running out of gas…and the heat pump performed well beyond its advertised specifications. We had a few -25C days and it was humming hard, but the house stayed a comfortable 20C inside. The house is around 3000sqft and we didn’t even get the largest unit, i can’t stress enough that they actually operate better than advertised.
We would run a fire from time to time but we did that with propane too, it’s mostly ornamental.
It's worth running the numbers based on your particular utility costs, though. In our case, with somewhat expensive gas and very expensive electricity, the heat pump would have cost quite a bit more to run: https://www.jefftk.com/p/running-the-numbers-on-a-heat-pump
With an air-to-water system like a Vaillant aroTHERM plus you could possibly achieve your break-even COP of 4.5 (the 12kW unit costs about US$7,200 in Europe, although from what I hear about the US heat pump market you'd probably pay like $20K for the unit alone for some reason).
(Also, how do you guys function with those strange units? Therms, BTU/hr, etc. - all so confusing. Surely electrification and the shift to heat pumps could be a convenient excuse to start using watts (kW in this magnitude) for heat and joules (usually MJ) for gas!)
I do think an air-to-water could make sense for us, though it wouldn't be able to handle the coldest days because our radiators aren't sized to keep the house warm at the lower water temperatures it puts out. The main problem is figuring out who can install one, since it's a pretty unusual product here.
(You get used to whatever units you're using, and the US units make some calculations easier and others harder. If I could switch it all over to the SI system without massive transition costs I would, though!)
You might be surprised at how well cast iron rads can provide comfort at low outside air temps and low flow temps. (I'm in neighboring Cambridge in an old, poorly/non-insulated house.)
https://news.ycombinator.com/item?id=39144329 has a bit of details on the experiment I ran back in 2022 to prove 135°F flow would work for us. (If you have a condensing boiler, you can run this experiment safely; if you have a non-condensing boiler, you can run it, but not for very long as you'll be damaging the flue and boiler with condensation at these lower temps.)
My outdoor reset curve (sadly, on a gas combi boiler because of the "pretty unusual product" factors) is now set to 105°F at 55°F OAT and 154°F at 0°F OAT (which is lower than the design temperature here, but it gave me more resolution to tweak the line to fit the loss just right; it's spot-on on the lower end, with the system running 22-24 hours per day when it's cold out and stays that way up until around freezing, where the utilization falls off).
Matching the gain to the loss quite closely has resulted in a house that's the most comfortable since we moved in in 2007 and gas bills with the combi went down about 46% (versus a 1990s oil-to-gas conversion of a 1950s boiler, so not a realistic comparison for anything that wasn't built by General Motors [not a typo]).
We have one loop with cast iron radiators, but the other two loops are modern baseboard. When we installed a condensing boiler in 2015 I needed to adjust the outdoor reset curve up so the loop that serves the first floor wouldn't leave it under temp on cold days.
Even our cast iron radiators are smaller than you might expect for the age of the house, because they were designed for water above its normal boiling point (using mercury pressure: https://www.jefftk.com/p/mercury-spill).
I also have one loop of modern baseboard. Fortunately, it's in the attic conversion where they did insulate the rafters while doing the conversion, so it works even at that lower temp. I did do something slightly unconventional in plumbing that zone in a primary/secondary and it gets the water from the boiler "first" and returns it to the primary loop ahead of the main zone which is all cast iron rads. That means the baseboard gets the hottest water possible and the full potential flow from the boiler if it "needs" it. In practice, that zone tends to only run 4-5 hours per day while the main zone is running 22-24 hours, so either what I did works really well and/or I didn't need to do it in the first place.
But, you've already discovered your reset curve with modern equipment, so you know the right answer for your place.
Thanks for the story on mercury pressurization! Fascinating. I learned a lot about our old house (originally gravity circulated as well, but near as I can tell, pressurized only to the typical 12-15 psi and with an in-ceiling green steel expansion tank: https://structuretech.com/wp-content/uploads/2020/03/Old-sch... )
(And of course, sorry to hear about your contamination inconvenience and expense!)
Jefftk I'm in the same boat -- what I'm going to have to do if I want to do the air to water heating is bring in a booster/combo unit that will boost the water temp to make the house the right temp. So I'm still tied to gas but much lower amounts - heat pump does the majority of the work and I still have protection on very low temp days.
Hmm. I wonder if adding an air-to-water pump to the existing loop, before the boiler, can be made to work? Perhaps with a microcontroller intermediating the thermostats on both to turn each on at the ideal time?
There are products that exist for that, though as always: maybe not in your market.
Over here they're called hybrid heat pumps and are quite popular. (At least with those that offer to sell them.) They're used in improving existing gas powered solutions. The heat pump takes most (or usually all) of the heating, while the existing gas heater provides hot water and can add peak heat if needed.
Can you point to some of those. I am curious at other options for my own heating operations but the landscape is difficult to navigate as a consumer and then you need to find people capable of helping out.
- Remeha, with the types Elga Ace, Mercuria, and Mercuria Ace
- Nefit/Bosch with Nefit EnviLine hybrid and Bosch Compress 7400i AW
- Vaillant aroTHERM plus/pro/split
There's also the Quatt Hybrid, which I haven't heard of before, but it looks nice. And according to their website it has a large market share.
100% agree. Our electricity costs are fairly low, and its a very low carbon source (mostly hydro electric + nuclear), so for us it makes a huge amount of sense. If you're in Alberta, where most of the electricity comes from coal...theres no logic in switching to electricity.
I'd argue that's politically motivated and very deliberate however...
Almost all coal plants in Alberta have been shut down and it's a small minority of net generation now. Natural gas has taken up most of the slack, but there's actually quite a lot of solar and wind generation in Alberta considering the politics (though that's likely to slow down now).
Ah i didn't realize the coal plants were retired! That's good to see. I was looking at the carbon impact per kwh in Alberta earlier in the year for a project I was working on, and was surprised how high it was. I guess other areas of the country just have a lot of other sources diluting the impact.
We got a heat pump installed alongside the gas system, since it's still working.
I would love it if there were a service or some code to look at 1) gas prices 2) electricity prices 3) how efficient the two systems are and switch back and forth depending. Like... if it's -10C out, run the gas. As it gets closer to 0C, switch over at some point.
If gas is flat out always cheaper, you could still put a cutoff point where you're willing to spend a bit more because it's better for the environment.
Depends where you are. Gas is certainly not cheaper for us. I did the math based on cost per KWH of fuel consumed v's the efficiency of the unit producing it. Natural gas would be slightly more expensive (marginal though...2% or so) but propane is around 3x more expensive, and with many people on oil the math is even worse.
In many regions electricity isn't as cheap as ours though, so that changes the game.
>Historically we drop a cool $3k a year on propane.
Similar to our situation, also in Canada; we cut our fuel bill by 3/4 after getting a heat pump. I still run the furnace on the coldest days, because it's hard to beat. But 9 days out of 10 the heat pump is all we need. The fact that it doubles as an AC unit (and is even more efficient) is gravy.
I also bought a heat pump hot water tank, and so far so good.
I live a few 100 km east of there and just had a heat pump installed last fall. I still have to spend $800 a year on wood but now my home is 20 C all day every day and I no longer have to break the ice on the dog's water bowl in the mornings. I still fire up the stoves to keep hydro costs down and so far the hydro bills haven't been particularly different from previous years when I had to use supplementary electric resistive heat. Then again, it's been a particularly mild winter with zero days below -30.
This winter was really mild. I was curious if we'd spend more or less, and honestly i wasn't super concerned. My napkin math suggested it would be comparable, but come with the benefit of reducing the risk we'd run out of gas. The propane truck cant make it up our road from late November early April, and last year we got down to around 20% remaining (which is around the point where the tank stops working due to there not being enough pressure).
Huge bonus that its been cheaper, and substantially...but I just love relaxing about the reduced risk of the house running out of fuel.
Did you consider putting up solar to counteract the additional electrical load? Sure it would take 7-10 years to pay off the solar asset but after that its free electricity and heating. Something I'm playing with but its a bit more difficult in the city.
Looks like it. I'd suggest anyone looking at a system like that install at least 2 separate outdoor units. That way if one breaks the other can still work - and most of the year it will be powerful enough to handle the whole house (some rooms will be a little uncomfortable but bearable)
This needs far more attention. Combi boiler installers tend to massively oversize the CV. But with heat-pumps you need to be far more accurate. And it does not make sense to design for a temperature that occurs only a couple of days in the year. You can just have the backup heater kick in which is far more efficient for a couple of days than having a heavier heatpump for the rest of the year that can not modulate back as much as a smaller heatpump.
> than having a heavier heatpump for the rest of the year that can not modulate back as much as a smaller heatpump.
Aren't basically all modern heatpump variable speed, and thus can modulate back?
That said, I totally agree with your overall point about right-sizing your heat pump, but it is more about saving money on the unit rather than worrying about cycle times.
Modern heatpumps can modulate, though it isn't 100%. I recommend people consider two smaller heat pumps in many cases - it costs more upfront but can modulate down more and if one system breaks the other can handle everything most days of the year (some rooms will be a bit uncomfortable)
Most heat pumps fall back to electric heating when it's too cold. So, on these few days you will need the same amount of electricity a typical electric heating will need.
Hyper Heat is a tech that is on multiple different models of Mitsubishi. All of the SVZ (ducted air handlers attachable to Hyper Heat or H2i mini-splits) do support (optional) electric resistance heater kits.
That’s correct, air handlers for ducted systems can absolutely have heat strips. That’s actually pretty standard. I have never seen one for a mini split though — can you share a link?
Whether you call that mini-split or not is up to you, but it's definitely a heat pump system that is Hyper Heat and supplemental electric heat capable, and getting down to one-ton units seems "mini" to me.
Mini-split means "smaller than conventional system ["mini"], condensor and evaporator are connected by long refrigerant lines ["split"]". It doesn't necessarily mean "wall/floor/ceiling indoor unit that has no ducts", though a "ductless mini-split" is the most common configuration of mini-split (because of the cheapness and ease of installation). https://zeroenergyproject.com/2022/03/09/what-is-a-mini-spli...
which spikes the electricity demand from the grid and puts it under the most strain when its most critical for the grid to stay up, which means the grid has to be overdesigned, which means that the air based heat pumps are a poor choice for a reliable grid.
I don't think this conclusion follows. It is true that variability is a challenge for grids, but it is not clear that it is better to trade more total energy usage (per useful unit of work) for less variability. Variability is certainly a challenge, but not an insurmountable one, and also one that must be faced regardless nearly everywhere, as solar power has become too cost-effective to be ignored.
The UK is rolling out smart meters to every property. In the past 2 winters (following on the Russian gas crisis), they have run programs that pay £3 per kWh reduced demand. This is a nice way to balance the grid during extreme demand.
It's called the National Grid ESO scheme and you sign up through your supplier when it's open. However, some suppliers take a cut of the ESO payment. Alternatively, you can sign up to Uswitch Utrack (https://www.uswitch.com/mobile-app/), which passes 100% onto the customer. (Disclaimer: I used to work at Uswitch.)
It depends on where you are. In many places worldwide, extreme cold is also generally quite clear from clouds unless you're literally in a storm, in which case, the high winds are just as likely to cause problems. Rooftop solar should be more than enough to offset your own usage.
In nearly all places extreme code means dark! Sure there are less clouds, but the latitude is high and so there are not only few hours of daylight, the earth's angle is also working against solar.
Depends on how many of those days there are. If it's only half a dozen or so, I can deal with putting on an extra layer of clothing in the house for a handful of days per year. As long as it's warm enough inside to prevent damage like pipes freezing, a small amount of personal discomfort for a few days is acceptable.
>Some naysayers will say that it doesn't work the 3 days of the year where it's -15°C outside,
That used to be true but modern air-source heat pumps are better. But even so the efficiency drops it's just physics. Even if a heat pump can grab heat at -15C it will need to run longer when it's very cold, reducing lifespan of the unit. At some point it will just switch over to pure electric so your power to heat 1:4 is now 1:1.
Ground source heat pumps are far better and even more efficient that air source but quite expensive to install.
-18°F here (-28°C) here this winter. The heat pump (Mitsubishi) definitely worked hard and burned through our net-metering credit, but it did what we needed it to do. -15°C is just not even remotely a problem.
> Disclaimer: I self installed one for my house (13kWth) and I'm very glad I did
My HVAC guy keeps telling me to install a couple of heat pumps (he doesn't like driving out to me), solar panels, and an in-house battery; what sort of complexity was this job? Are there online sources you used?
With this sort of work let the HVAC guys do the research for you. Call 3 of them get quotes. Then research what they are offering. Pick the one you like. Last time I did this around 2008 it was about 5k-15k I was quoted. I asked all 3 for a small, medium and large systems. For me it was mostly an in place replacement. The ducts were already there. The refrigerant lines were all ready in place. The biggest cost was the unit themselves and some change out of the controllers. The labor was about 1 days worth of work for 4 guys.
You can also gain quite a bit by just fixing drafts and putting in proper insulation. Which can be much cheaper to do. I also had the guys go thru and fix an leaks in the duct system. That way the air was coming out where it should. It is amazing how badly that is installed many times. I also had them put in an attic fan which vented the attic when it got to about 110F. Insulation would have helped more there and I screwed up and put it off. If your house is older than 2000. I say go thru and review the existing insulation and look for drafts first.
It trimmed my bill from about 350 a month to 200. My new house has excellent insulation the house is slightly bigger and the power bill is in the 80-150 range (less because I got solar, but I figured out the actual cost anyway). It has one unit and an air valve to switch between the floors. So the total cost is lower but the one unit will run longer. That savings I am getting is mostly because of better insulation.
Installing heat pumps doesn't require a ton of domain knowledge (assuming you're already a handy person), but it's a lot of work. It took 3 guys who do it for a living 160+ man hours to install our mini-splits. They had to drill through walls, attach channels to the siding, crawl into a tight crawlspace, do some plumbing when they hit a water pipe with their drill, wire up electrical, and add breakers to the panel.
The only thing that might catch you up is designing the system and ensuring you right size it for your heat load requirements. I'm sure you could research this pretty well, but your HVAC guy might also be happy to consult on that portion.
Just to be clear, it works perfectly at -14c and above? Or is there some disappointing performance in an intermediate range?
I'm in Northern England and it's not uncommon for weeks of -5c to 5c in winter, some snowy days, plus serious damp making it feel even colder. So I'm curious if a similar system would be similarly amazing here.
I've read many people say they work perfectly because it won't hit -20c (a nice Strawman...)
At low temps COP is lower, meaning you'll not get 4 units of heat for 1 unit of energy spent, but COP is still higher than 1 meaning using heat pump is still cheaper than using basic electric resistive heating.
I think Northern England climate is ideal for heat pumps -- it never gets too cold, never gets too hot.
We moved to heat-pump a few years ago and disconnected from gas. It's been working great. Our biggest expense was insulating our house. It is an old house and the 2nd floor was very drafty. You could feel a breeze coming through cracks in the wall. When we opened the wall there were just a few newspapers in there and no insulation.
We had the 2nd floor siding removed, an extra layer of insulated wall added to the outside and then cladded with siding. It was like putting a big insulated hat on our house. Now the temperature is very consistent and absolute no drafts.
The architect said to me that we'll never fully recoup our costs of putting the hat on the house. To which I replied that we don't always to things for economic reasons, and just do them because they are the right thing to do.
My only regret was going with a Rheem heat-pump water heater in this mix. It does not perform well at all. With hindsight I would have looked for a way to perhaps have water heating integrated with our air heat-pump system. There is a company called Arctic that has those systems.
Also with regard to heat-pump water heater, out big problem is that a hydronic floor heating system (installed when we were on gas) is now constantly drawing off heat from our tank. I'd like to find a small standalone unit to handle floor hydronic heating separate from my main water heating.
> The architect said to me that we'll never fully recoup our costs of putting the hat on the house. To which I replied that we don't always to things for economic reasons, and just do them because they are the right thing to do.
I am so frustrated with this analysis and sentiment when it comes to environmental investment. I understand that looking at it with a financial lens can and should be done to inform what we do, and it would be great if a project just paid for itself, but you look at all the other things we spend money on and the same calculus is not used.
People don't buy the cheapest car, house, clothing, or food they could possibly get by with, or analyze the marginal cost of moving up or down the possible price tiers available to them with only the financial payback as a guide. Yet we constantly hear the refrain that you shouldn't spend a given amount of money on solar, house improvements, appliances, etc. that might be better for the environment if the payback isn't somehow positive with a 10-20 year payback period.
I've constantly had to work with contractors to let them know that I still want to pay for the marginal costs associated with investment even knowing that the marginal financial benefit is smaller. For instance, with solar panels in less than ideal locations, tri-pane windows, etc. I have disposable income, and I think the world is trouble for the 8+ billion humans inhabiting it, so I think it's worthwhile that I would spend some of that to make it marginally better even if that means I don't have a positive financial return.
It's a much more complicated equation, but it's very possible the emissions from simply producing the insulation and having the install done are more than the saved future emissions.
Insulation pays back over a long enough time horizon (economically or CO2 wise). Although spray foam at the moment does have a large CO2 impact. If someone is putting in way too much insulation then we could say that the last 30% of insulation wasn't worth it. When people say something won't payback economically on a home, they are usually looking at a time frame of 10 years or less.
In this case the insulation itself will probably payback quickly. The problem is the cost of re-siding the house to get the insulation in- likely similar for CO2 impact.
I absolutely agree this kind of nontrivial work can be done in a way that is woefully inefficient/impractical. My EWI, approx 85m2 of graphite polystyrene with an embedded CO2[1] of ~15kg/m2 is equivalent to approximately 1.5 years of CO2 emissions (combined electricity & gas), or ~9 months of CO2 emissions before I replaced windows and old kerosene boiler that came with the house.
Actual installation and other materials excluded (adhesives, mesh, silicone render, 450 hot beverages, getting the neighbour's car repaired after the scaffolders hit it, etc.) excluded.
I don't have a full year of data yet, but all in it's looking like CO2 emissions are going to come in at well under 40%. This is in line with the independent assessment I needed to clear a grant for some of the costs[2].
It seems to me "carbon ROI" is about 1/4 the financial ROI (est 8+ years).
Now if it was PU instead of EPS that would be a different cost (10x the CO2 of polystyrene). Sadly I also ended up with some PU (PIR) in a small area of low-pitched roof void, I don't know if there were better choices there.
There's also a hidden cost in living in a cold, damp building - now there are winter days when I don't even turn the heat on at all.
> People don't buy the cheapest car, house, clothing, or food they could possibly get by with... Yet we constantly hear the refrain that you shouldn't spend a given amount of money on solar, house improvements, appliances, etc. that might be better for the environment if the payback isn't somehow positive with a 10-20 year payback period.
I think the key thing here is that energy is 100% fungible unlike your examples. A kWH is a kWH.
But you’re not buying kWh in this example. You’re buying home energy systems. They have many tradeoffs, pro and con. Besides that, for many people, a kWh produced by a renewable energy source or that’s available to them when the grid is down is worth more than one produced by a coal plant that might be unavailable during an outage.
No, it really isn't. Your house might lose the same total energy as a super efficient house, but if all that energy happens to be lost through a cold spot by your dining room table, you're going to get pretty fed up with the situation.
It's not just an environmental consideration - efficient houses are much more pleasant to live in, particularly if they are designed holistically with proper ventilation systems and few cold spots.
It shouldn't be a surprise. Our economic system and even economics-related media puts individual short term gains above all else. Everything is viewed through the lens of "what makes me the most money today?" Long term positions are not valued. Positions that might benefit others are not even considered.
> The architect said to me that we'll never fully recoup our costs of putting the hat on the house. To which I replied that we don't always to things for economic reasons, and just do them because they are the right thing to do.
The outter layer wall that was added was wood studs, rock wool insulation, then wood siding. Looks great, no drafts, even temperature year round without having to run the heat-pump much. We also have an ERV to keep the air fresh in the house.
No one will pay more for a house with a higher R-value. If this were a determining factor, it would be part of real estate listings. It's a secondary or even tertiary concern for most people.
If a home were priced as little at $200,000 then 20% would cover $40k in investments. Homes around here don't sell for the little.
Assuming your percentage is correct and home prices are much bigger it makes it seem like a spectacular investment. Actually too good to be true of an investment.
If the return were 2% or max 5% I could see it maybe not being worth it depending on home prices in your area.
If you're buying a house without asking for the trailing twelve month energy bills, you are an unsophisticated real estate market participant and will pay for the ignorance over time.
In the US, this is so true and sad. After building my first home with insulation way beyond code I learned the sad lesson that it won't get you a dime more when it is time to sell.
We keep in touch with the new owners who have since thanked us for building so well. Their bills are much lower than any in the neighborhood and they had no idea.
The same goes for heat pumps. I'm living in my third build and we had room to do a ground source heat pump. It is amazing and my bills are half of what my neighbor pays for a similar size house. Mine is also better insulated. When it comes time to sell it, nobody will care.
The US needs to up the codes on insulation. Hot climate, cold climate - who cares, it helps.
> so I think it's worthwhile that I would spend some of that to make it marginally better even if that means I don't have a positive financial return.
Your action is going to make close to 0% difference for the 8+ billion humans inhabiting the planet. So from a practical standpoint, you've failed, but that practical failure makes it clear that the gesture has pure symbolic value for you.
And since that symbolic value stands in stark contrast to incessantly chasing positive financial returns: task failed successfully. Congratulations!
From a practical standpoint, they have valued their energy savings closer to what the true cost of carbon emissions are (remember, most carbon emitters are in no way paying the true cost of their emissions [1]; this externality dumping continues with wild abandon).
You're arguing systems and scale. This person is simply early in the adoption curve. Consider what will happen when this happens more broadly. As the climate situation becomes more dire [2], the price of carbon emissions per ton will rise and the willingness to prioritize energy savings and carbon emission reductions should increase regardless of fiat return. Physical system outcomes are distinct from magic number in database goes up.
But sure, if you're already poor and have nothing [3], this won't matter to you and your life trajectory is already mostly locked in today. As nullstyle mentions, we need to compound in the positive outcome direction, and those decisions are being made today.
This is a tough one, honestly. For one, being at the early adoption curve also has you on the low side of efficiency. If things aren't being done at scale, they are likely fairly low on that score.
More, though, moving to something that gets you a more climate controlled home in the name of efficiency is odd. You could almost certainly use smaller scale solutions to get more comfortable living that does not involve such a drastic change to the home. Clothing and lifestyle changes are things you can do, for one. For two, though, if the place was so drafty you could feel a breeze, it almost certainly did not have active heating/cooling to the level that they built up to. Such that is seems odd to justify how efficient you could do something that was just not getting done before?
No reason not to do it, of course. But insulation is an expensive thing to add to a house. Not just in raw costs, mind. Most insulation materials are of dubious carbon neutrality. And nothing lasts forever, least of all housing.
Insulation is one of the cheapest improvements than can be done to improve energy efficiency of a structure. Once insulated, those energy efficiency gains persist for the life of the structure. Nothing lasts forever, but homes have a 100+ year service life.
Homes have a 100+ year service life? Where? I see the median age of housing stock varies heavily in the US. Quickly scanning other markets, I see EU has older housing, in general. Even there, though, they don't talk of 100+ year old houses as being that common.
Scanning websites on this claim, I see that "properly installed, with no damage" some types claim up to 100 years of service for insulation. I strongly suspect that that is a claim that will not hold for the vast majority of homes. More reading also strongly suggests that if your house was built prior to 2005, you probably need to get the insulation redone.
Worse, from my experience, the older the home the less likely you are to have subfloor/walls to actually install insulation. Heaven help you if you do one of those container homes. And if you live in an environment where you have heavy rains or hail, expect damage to creep in rather quickly.
Don't get me wrong, I support the idea that adding insulation is almost certainly a good idea where you can. I just can't bring myself to trust claims of 100 year service life.
Depends on the country. A well-built and properly maintained house in Germany can have a service life of 80 to 100 years or more. Some may even exceed this range, especially those that are regularly updated and renovated.
German building standards contribute to the longevity of residential buildings.
A well built and properly maintained anything can last hundreds of years. Proper maintenance likely involves heavy replacement of parts, mind. And is very contingent on no damage.
I will add I just moved out of a hundred year old house in Seattle. I know they can happen. I also know that house had no air conditioning and retrofitting one on would have basically meant a new house. Even if it looked the same.
> As the climate situation becomes more dire [2], the price of carbon emissions per ton will rise
Looking at what's happening here in Canada, where it looks like what has high chances to be the next government is campaigning on getting rid of the carbon tax, these days I'm somewhat pessimistic that carbon pricing will actually be implemented by the top contributors to global emissions. I hope I'm wrong.
Literally every single accomplishment in human history was built upon millions of small "symbolic" individual actions. Good things don't just magically happen on their own.
“Close to 0% difference”, compounding over time was how we got here. I’m not saying personal responsibility is the only factor, but youre the wrong person in the exchange above, and OP has the proper attitude.
> The architect said to me that we'll never fully recoup our costs of putting the hat on the house.
Your architect is almost certainly right. I would bet that most of your improvements came from fixing the drafts, with the insulation providing a marginal improvement on top of that.
I’ve also dealt with insulating old homes, but I did draft fixes, wall insulation, and attic/roof insulation at different stages. The draft fixes provided the most improvement, followed by attic/roof insulation. Insulating walls had much less effect than I anticipated.
In friends’ houses I’ve used my thermal camera (which I didn’t have back then) and it’s easy to see where the heat or cold is coming in during weather extremes. These days I’d recommend anyone start with the thermal camera view before deciding where to spend money on insulation.
> Insulating walls had much less effect than I anticipated.
I wonder if that's due to air already being a decent insulator and walls have sizeable air voids. As long as you cut out the drafts, the air in the walls should remain a decent insulator. It's also my understanding that the draft treatments are at least as important as the insulation work which is done when retro-fitting insulation. One reason attic insulation would make a much larger difference is most homes with attics use vented soffits designed to encourage airflow. They are built to be drafty and you can't seal up those drafts without redesigning things.
Depends what your walls look like inside. If it’s balloon framed with no blocking, you’ll have a good convection current inside the wall.
The moisture concerns when trying to add insulation to an old uninsulated house are real, in service of saving a few thousand dollars of heating costs you could literally destroy your house and your health with mold.
Oh I’ve seen buildshow. I have also seen him talking about mistakes he made in the older designs he had. I would be real cautious about letting a builder at a lower tier than him beta test their ideas on moisture control inside my walls when I’m the test dummy inside.
Even if you don't use a thermal camera, just the thermal thermometers work as well. Sure, you have to take more readings, but the result is the same. A lot of people probably have one of these now after Covid, and can at least test things out before going to the step of a full thermal camera.
I have a bedroom that has a shared wall with a water heater which causes this room to be hotter than the rest of the house. Using the thermometer showed the temps after I added a barrier to the inside of the utility closest dropped significantly.
I bought a Topdon TC001 a year ago that in my experience is significantly more responsive and higher resolution than similarly priced FLIR or other name brand options at that price point. It appears there are even more low cost options now.
I find it rather interesting that companies like FLIR are limited by regulation (I believe US export bans) from selling IR cameras with greater than 9fps. there is also a resolution cap but I forget what it is off-hand. Strangely enough this doesn't stop US citizens from purchasing higher performing cameras from non-US companies. I think technology has come down significantly in price over the last few years and you can now get smartphone attached versions like infiray for a few hundred bucks.
Very handy for checking for drafts and cold spots, and also checking the fuse box and other electrical for hot spots.
The resolution is not amazing, 206x156, but it's enough for this type of work.
I have a friend who is happily using a flir one, with a resolution of 160x120 at his day job as an electrician and it is also enough for checking for draft, water leaks insufficient insulation, etc.
There’s a couple of big problems with the heat-pump industry in the U.S. First, people get their advice about HVAC from the tradespeople, who are way behind the curve on heat-pump technology. Second, and relatedly, the trusted American HVAC brands are far behind China and Japan and Europe on heat pump technology, especially cold-weather capable inverter units.
I had our heat pumps replaced here in Maryland in 2019-2020 with mid-range Amana (rebranded Daikin) units. Decent efficiency, but output drops to half at 10F. The guys who recommended the system, a trusted local business, didn’t even tell me about that. Even in Maryland that means waking up to a cold house several weeks out of the year. That means we needed to keep our oil-based backup heat in place, which is a huge expense to maintain. (Also, our HVAC guys didn’t know that the communicating Daikin units can’t control external auxiliary heat, so they just left things with no backup heat whatsoever.)
After educating myself about this, I wish we had installed one of those Chinese inverter based units, like the Gree Flexx. But if I asked my HVAC guy about that they’d stare back blankly. And the folks who do know what they’re doing can charge whatever they want. The price of getting a mini-split installed here is several times the price of the unit. The $16,000 we spent just a few years ago for two condensers and air handlers looks downright cheap compared to what it would cost today.
Regarding your floor, we have a similar situation with radiant heat in our basement slab. I’ve been looking to ditch our oil boiler, but there’s basically no heat pump options that are widely available. (I don’t want to install some imported Chinese air to water heat pump that the local guys can’t fix.) With heating oil prices being over $4, though, I’m looking at just biting the bullet and installing an electric boiler, which is at least something I could probably fix myself.
I feel you. The lack of knowledge among American tradespeople is infuriating. As soon as you deviate slightly from the brands of furnaces they have been installing for decades, they don't know anything.
I think the biggest hurdle to heat pump adoption (at least in North America) is likely to be that it provides an experience that simply isn't as good as a gas furnace. On a chilly morning the air coming out of the vents just isn't that warm and it may take hours to bring the house up to temp, whereas gas puts out pleasantly warm air immediately and can quickly warm the house even on the coldest days. When it's truly cold (like < 20F) the heat pump will run continuously and struggle to maintain temp. Don't misunderstand, the heat pump is certainly _good enough_, but people typically don't pick the "good enough" experience over the "better" experience when the better option is available and they can afford it.
For reference I've lived in NC and TN near the mountains where heat pumps are pretty standard. I imagine we don't get the ultra high efficiency cold weather heat pump units that would be used up north, but they also get much colder temps than us. Several of the houses I've lived in have been recent construction (2008 and 2018), so well insulated and reasonably new & efficient heat pumps. For the last 2 years I've been in a house with gas, and it's just so damned pleasant... I know on paper that heat pump is better, but I really don't want to give up that furnace.
A relative recently upgraded their 120yr old house with heat pumps, and the warmth is so much better than where I currently live (a 40 year old home with a new gas furnace). In my experience you can't generalize about heat source.
It doesn't have to be all heat pump. You can have a backup gas heat for the coldest days, or even resistive heat. I'd bet there are heat pumps that integrate those technologies to ensure a nice experience.
When I got a quote to upgrade my resistive heater to a heat pump, the added cost to get a backup resistive heater (with the same capacity as my existing one) was only $500. Seems like as long as you're wired for it, it's very cheap.
> I think the biggest hurdle to heat pump adoption (at least in North America)
> When it's truly cold (like < 20F) the heat pump will run continuously and struggle to maintain temp.
Luckily, pretty much the entire Western and Eastern Coastal areas, it doesn't actually get that cold on a regular basis, except a few days in the winter. The US is actually in an incredibly advantageous geographical position for at least 60% of households to be on heatpumps, as opposed to, say, Finland/Canada/Russia etc.
Meanwhile it was estimated that half of Swedish houses were equipped with heat pumps in 2016. That number has certainly not gone down since given the steep rise in electricity costs we’ve had since. Many houses have been converted from horribly inefficient direct electric heating to heat pumps.
Part of the problem is that heat pumps aren't really well suited to a use case where you frequently have to bring a house up to temp in the way you're describing. If you have a big overnight set-back and then the heating comes on in the morning, that will require much more heat output than constantly putting out enough heat to maintain temperature.
In a well insulated property, the greater efficiency from operating at low output temperatures outweighs the additional heat loss from no / a low overnight set-back. In a poorly insulated property, the optimum set-back is higher and the efficiency at that optimum point is also much lower because the heat pump has to operate at higher temperature in order to ramp up the temperature.
I don't know if they are available in North America, but in the UK we have hybrid systems available that use heat pumps for 80% of the annual heat load and gas for peaking / ramping. OpenTherm gas boilers can be retrofitted to be controlled in this way so you only add the heat pump. An air source heat pump driving a hydronic / radiator system in this climate can serve 80% of the annual load with a unit sized at 55% of peak heat load. Different climates will have slightly different numbers but it shows the power of a hybrid system as you save a lot on HP capex and also maintain redundancy.
The advantage of this system is that the failure-mode of an incorrectly sized system is an efficiency penalty rather than not being warm enough, the same as an incorrectly commissioned or sized gas system. (Most gas systems are not optimally sized or configured and are delivering 5% to 10% less efficiency than they could).
I don't know if these systems are available in ducted air configuration for the US market though.
Wait - you have a HPWH connected to a hydronic floor system? That's an extremely inappropriate setup - the heatpump on a rheem is probably like ~4000 BTU/hr, and it's pulling the heat from the conditioned space, then you're drawing it off and pumping it back into the space via the floor. If you don't have an air-to-water heatpump and don't want fossil fuels, just use an electric boiler.
That's a shame about the Rheem. Ours has been overperforming my financial model in the standard eco mode. We do have an advantage in that it sits out in the open in the unfinished part of the basement, which runs slightly warm in the winter due to a ductwork problem. No venting was necessary.
It's definitely challenging to find trades who have both the knowledge and interest to innovate relative to standard HVAC installations in the area.
On the payback period, that’s probably just outlay divided by energy savings. I’m sure you’d get more enjoyment from a more comfortable house and the next owner will appreciate the modernisation too so those need to be factored into the investment appraisal.
I doubt the architect puts such a miserly lens on the other projects they’re involved in.
This is actually becoming an important point. In parts of the world where energy ratings matter, they have an impact on house value as well. They unlock incentives, etc. A house that is up to modern standards is simply worth more because any new owner does not have to do expensive renovations to modernize. In the Netherlands house flipping is pretty common. Buy something old, modernize it, live in it a few years and make a profit. The lower energy cost is both a nice bonus and a key selling point.
> My only regret was going with a Rheem heat-pump water heater in this mix. It does not perform well at all.
Heat-pump water heater's performance depends a lot on where its installed and the airflow+heat available. If the water heater is undersized or if there isn't enough heat in the air, it would perform worse than a standard gas/electric water heater.
Mine is installed in a closet under the stairs, which is not ideal, but as long as I keep the water heater in eco mode, and keep closet door slightly open, it works good enough for our usecase. Our annual water heating costs went down from ~$500 to ~$100 after switching to the heat pump water heater.
As in the cold end of the heat pump is inside the heated area of the house? That feels very weird. On the other hand with heat pumps, stacking multiple stages strategy isn't necessarily a bad thing! All inefficiencies are not really losses but merely resistive heating contributions (unless their heat escapes to the final cold sink aka outside) and in the end the real question is which configuration is good in terms of capex and maintenance.
In an environment where getting rid of humidity is a concern (mold!), a "cold end inside" heat pump for water might even double as a dehumidifier, with water condensing on the cold end sent to the sewers, contributing a little energy in the process.
What problems are you seeing with your water heater? I’ve had one for about a year and have been pretty happy with it after learning I needed to schedule high demand times of day. It is a bit louder than I’d like but it’s not horrible.
> The architect said to me that we'll never fully recoup our costs of putting the hat on the house.
That's only true if value your added comfort at a very low price. The problem is that it is hard to put a value on the comfort of a house, either while living in it, or while selling it. Hotels, however, do it all the time, but it's easier since they are in the business of selling comfort at various levels.
That's right. I remember a local "electrification festival" where some vendors and city officials teamed up to explain the various options. One of the most common questions was "will this lower by bill"? And the most memorable answer by a vendor was "probably now, but you won't have to be wearing that coat in your living room". Which hit home because at the time we had a drafty house with poor heat distribution.
My understanding is that any house that isn’t built ‘tight’ by today’s standards will have a fast enough ACH that you don’t need to worry about ventilation as you would with a tight house. And only a ‘deep energy retrofit’ of an older house would result in tightness like that, so ERV and MUA etc are not necessary. Local code, build detail, and age of house are factors, YMMV, but this isn’t a problem you’d cause by accident with anything but a very invasive retrofit.
Mechanical ventilation is not necessary in a drafty house, but it’s still very nice to have. Bonus points for a well-filtered system. (None of the major brands will sell you a system that is well filtered out of the box. But it’s straightforward, if rather space consuming, to put a monstrous filter with effectively zero pressure loss in series with the system.)
Bonus points for taking advantage of a balanced ventilation system’s ability to continuously extract air from stinky areas, e.g. bathrooms.
Even more bonus points for avoiding negative pressure due to conventional bathroom exhaust, which can defeat stack effect-based exhaust from non-power-vented combustion appliances, which are, for some reason, still legal.
(Seriously, WTF. There’s a straightforward design that could safely created a forced draft even with legacy leaky ductwork: put the fan on the exterior vent terminal, so the duct is under negative pressure. The wiring could be fished through the existing duct using class 2 / SELV wiring with high-temperature insulation. A pressure or airflow-sensing interlock in the appliance could prevent gas flow if the fan stops working. Sadly, I’ve never heard of a system remotely resembling this. The choices appear to be stack effect (category I or II) but basically crossing fingers and hoping the pressure works out) or positive-pressure sealed but not tested “category III” or “category IV” pipes and crossing fingers and hoping that the pipes are actually airtight.)
Yeah I believe GOLogic’s designs have the ERV exhaust in the kitchen, bathroom, and laundry, and the fresh air return in the living spaces and bedrooms. I definitely like the idea of that, especially with filtration.
They're as noisy as an AC. So here in Arizona no one cares. But in Belgium this was an issue as they run more in winter and in winter sound travels further.
Just installed heat pump systems (daikin) this december.
The exterior unit is basically silent even when there was a cold snap (below freezing but not northern alaska cold).
I suspect an interior air source heat pump hot water heater, being smaller, will be noisier, and likely less efficient.
I'd love to switch my 240v/30a water heater to use a 120v/20a service, but will wait a bit longer for the technology to mature. Ideally it'd have the heat collection part outside.
Uhmm...I see a problem for countries where you have wall to wall connected urban environments...If all 60 connected houses on a street, install external heat pumps, it will add up.
Turns out cities are loud! In NYC, at least, heat pumps are far more quiet than the endless window unit A/C's, or larger traditional A/C's, in my experience.
Outdoor noise is less of an issue in the winter in big cities because windows are closed.
Also, when talking about noise it's important to talk about frequency. If they produce low frequency noise, that can be far more irritating. Shutting the windows won't help much
Depends on the installer. A lot of noise results from units that are not properly mounted or mounted at a slight engine. The fan then starts getting more noisy and wears out earlier. There are other problems to not installing units properly.
Drain water heat recovery seems like the best efficiency boost for water heating. Completely passive, 60% extra heat energy. At least for cold climates. Heat pump water heater might be phenomenal in a Phoenix garage.
Certified performance rating data from virtually any air-to-air, air-to-water, etc., system sold in North America is available here [1]. This includes capacity, COP, and sound data. It also includes integrated performance rating metrics like SEER, HSPF, IEER, etc.
As-engineered and as-installed/configured figures have the potential for a wide spread. Both are useful, but as a homeowner, I’m interested in seeing my as-installed figures more than the manufacturer or test lab’s figures.
As a shopper, I’d want to see a nearby house’s figures as-installed by my prospective contractor.
A big factor for the total energy consumption besides the heatpump is the rest of the heating system.
For our house the yearly energy consumption of the heatpump is around 1.4MWh/y (for floor heating, warm water and cooling of the bedrooms in summer;this number is reported by the heatpump control system) but the hole heating system including all the pumps and so on is 2,55MWh/y.
It's important to note that those ratings are all tested under specific conditions that includes a rather short (~3m IIRC) lineset and other parameters of installation that in the field can lower the capacity as more energy goes to the pumping of the liquid refrigerant. Particularly the lineset length.
Also, the testing varies between "traditional style heat pump" and inverter driven "VRF" equipment.
That's not to say that the AHRI information isn't useful, but the numbers can be a little subtle to get to an apples to apples comparison and you should have a selection done based upon some real estimated line lengths and installation conditions.
A lot of these are UK based systems which are installed by installers with Heat Geek[0] training.
They're an interesting company who's trying to fill in the lack of training that traditional gas heating installers have to properly install air-to-water heat pumps in the UK. They also do homeowner training courses and a guarantee scheme on their certified installers (they'll fix the system for free if the SCOP is below a designed level).
They did a series of videos with Skill Builder[1] (who's a bit of a heat pump sceptic) where they fixed a badly installed heat pump that was causing a lot of issues. That install is currently 7th on the linked website[2] with a SCOP of 4.5 (450% efficient). Obviously a bit of a sale pitch from them, but there's loads of interesting information about WHY they're making the changes that they are.
I watched a few of their videos as well. Great stuff. Key take away is that there are a lot of installers that have no clue what they are doing. Which results in poorly performing systems. The issue is not the technology but the lack of training and experience.
Another good point is that even an old house with poor insulation can benefit from heat pumps. It just depends on sizing things properly and dialing things in properly. The UK has a lot of old houses that are quite old. This doesn't have to be a show stopper. There are a lot of myths and half truths around this topic. Of course you'll need more kwh for heating if your insulation is bad. But you should still get the same energy coefficients. And you'll pay a fortune in gas as well to get the place warm. Whether that's worth it with or without investing in insulation, windows, new roofs, etc. depends on a lot of things.
Most of the nonsense about heat pumps not working at lower temperatures is easily refuted by the notion that much of Scandinavia runs on these things for decades. Most of the people having issues with heatpumps are simply buying the wrong stuff, or having it installed wrong, or both. People have proper arctic winters in Scandinavia. Also there's a reason lots of Scandinavians ended up in places like Montana: it feels like home to them but with better summers (it's much further south). If people can do heat pumps in northern Norway, Montana is a walk in the park.
it's funny actually, i've been binging their videos the past few weeks, since i'm looking into buying a home in need of renovation, and was happy to see their logos as part of one of the default columns.
they claim also to be mainly motivated by the climate crisis and are even, now, developing an open source water heater, which... you don't often hear about in industries such as home appliances or heating:
https://www.youtube.com/watch?v=uFBbArwAXS8
i'd love to install an air-to-water heatpump myself, but i'm untrained and i guess i'm feeling a bit of the dunning–kruger effect while learning from the heat geek videos.
Heat pumps require some domain-specific knowledge to build a system that costs less than gas for the same building (the crossover point is near a seasonal average COP of 4.0 at UK's gas and electricity prices, as mentioned in other comments SCOPs of 4.5 are very possible). Yet there are subsidies available and installers without the knowledge (who would normally be installing gas systems) are installing them basically without sizing radiators correctly or by doing things that reduce performance (big buffer tanks, lots of zoning, extra pumps that are unnecessary, etc.).
So there are lots of horror stories of companies installing systems that don't work very well and cost a lot of money to run, which makes people think heat pumps are crap. But usually people like Heat Geek trained installers can fix such systems without changing the equipment - often both providing more comfort than gas (less thermal cycling because heat pumps with inverters can modulate their output more precisely instead of hard switching on and off) and costing less to run than gas.
I see, thanks. This provides a counterpoint to the sibling comment of "they don't perform but everyone blames the user for doing it wrong", but also sounds true, so hopefully as installers learn more about how to correctly install heat pumps, they'll perform better.
COP is Coefficient Of Performance, basically the heat they produce divided by the electricity input, so a COP of 4.5 means that 1kW of electricity produces 4.5 kW of heat (it's taking heat from the environment so you can say a COP of 4.5 means it's running at 450% efficiency, but that's only in terms of electricity use, not actual overall efficiency - but electricity use is what we care about).
COP is only an instantaneous measurement though, and changes depending on the outside temperature. So if you need heating for five months a year, and it's usually exceeding COP of 5 for 80% of that time but dips down to a COP of 3.0 on the three or four coldest days of the year, it's not really correct to say it's either >5 or that it's 3.0 - so SCOP is used as a 'seasonal' COP that is averaged over a longer time period, so you can compare different systems over the longer term.
COP (coefficient of performance) is taken at a full load condition with specific indoor/outdoor conditions.
SCOP (seasonal coefficient of performance) is a weighted average of performance at different load conditions that represent different outdoor conditions based upon an average binning of weather conditions.
Most if not all energy/green subsidy schemes in the UK in the past couple of decades resulted in tons of cowboys rushing after the gold, and doing a terrible job and even causing serious long-term damage to the property.
No different this time round I imagine.
It's so infuriating - literally handing money to conmen
Maybe. However a heatpump sized to cool your house in summer cannot heat your house when the temperature is below about -3C. The heatpump might be able to produce heat to -25C, but it is too small to produce enough. Thus my system (in the US) that I just paid a lot of $$$ to install last fall leaves me using the backup gas heat a lot more than I wanted last winter which is disappointing. (It did get below -25C last winter for 2 days so I'd need that backup heat anyway, but I was expecting only 2 days not most of a month)
A properly sized system will be based upon the worst of the heating or cooling conditions.
Luckily an inverter heat pump can run down to about 25% full load so even with them coupled and in an imbalanced heat/cool environment you can still see good performance year round.
British note: UK govt subsidies for some insidious reason are not available to "reversible AC" style systems, so the dominant form here is air-to-water.
I had mine fitted last year. Retrofitted to existing radiators with 8mm pipework. With natgas backup/hot water boiler. At the end of this month I intend to go back and correlate the bills against the previous year (both kWh and £), because like a lot of discussion in this thread I think the installers have made some poor decisions. There's too much poorly insulated external pipework.
The table in there assumes pretty high quality insulation and the neoprene-looking stuff doesn't meet that standard so would have to be thicker. Note that the way the performance of pipe insulation varies non-linearly with the pipe and insulation radius so it's a bit unintuitive.
How do I know? I had the same problem with my installers.
I have this outdoor unit https://cooperandhunter.us/product/ch-hyp36lcuo. This past winter the temperature dipped into -20C (-11F), had no issues maintaining temperature in the low 70s in the house. I was running them in heat pump only mode (resistive strips were not used).
In the summer our temperature regularly reaches into 90s (above 30C) and the house is very comfortable on those days as well with the same heat pumps
Hmm, that's interesting, we have fairly large temperature swings (typically -15 C in the winter to 40 C in the summer), so it'd be interesting to see if the heat pump could replace the AC unit and the gas heating.
I'm in a similar zone and replaced (delivered) propane with a ground source heat pump 2 years ago. Constant temperature indoors (3C warmer in summer than winter) with plenty of AC capacity to spare. Breakeven is about 5 or 6 years.
They work okay in my area for -1C to 46C, imagine for your range maybe you just get a model that has improved heating over a basic one, whether that means ground source, more stages, or a heating element.
I've watched a few videos of his and I'm not sure I'd characterise him as entirely skeptical of the technology as a whole, but more skeptical of the government incentives to retrofit.
He argues in one of his videos that there aren't enough qualified installers who actually understand heat pumps, and the government incentives are encouraging cowboys, basically, to take the government cash and provide unsuitable installations. Then secondly, a lot of the insulation installers also don't know what they're doing and are creating damp problems by neglecting ventilation.
Even as someone who is a huge fan of heat pumps, it's hard to disagree with him. There are a lot of difficulties with retrofits in the UK, where we have a lot of old terraced housing stock with poor insulation, no mechanical ventilation, and small gardens. Then on top of that, there are almost no tradespeople who actually understand the technology or why that housing stock is unsuitable without extensive improvements.
To be frank, even regular gas plumbers are shocking here. They don't install correctly rated systems, don't set the temperature correctly and don't enable the weather compensation functionality that is built into all modern combi builders and can save you 30%. They just install an over-sized boiler and whack the temperature up to maximum. At least it keeps the house warm, at the cost of inflated bills. That's without getting into the FUD about chemical water softening (and use of magic magnetic "water conditioners" instead), continued use of loft header tanks and not understanding how to improve or balance water pressure.
No they don't and it's kind of like agile everyone tells you it's not done the right way otherwise it would work. But when is sold it's sold as is it's great.. Very deceiving for customers
If you are in North America, I highly recommend to check out https://ashp.neep.org/#!/ to compare heat pumps. It has efficiency and technical data on almost all models easy to compare without the marketing bullsh*t of manufacturers. The tests are conducted independently and instead of one COP you get the COP depending on the outside temperature which very important in cold climates like Canada.
I see tables, I am exited. But I can't make sense of what anything is? I know COP, but what is Training, what is Source? MID seems to be a kind of sensor? Some of the table headers have a tool tip explaining things, but are the ones that aren't the most needed. Also, some about page about what the table aggregates and how it gets there? Seems to be some kind of aggregator for information gathered from an appliances called "emonHub" which is a rPi that gathers data from an assortment of other devices. There are some jargon that you have to parse, ("supply" means the electric cables that "supply" your heat pump) to understand what's going on.
I just want to throw this out there to this audience. As someone that has worked in and been interested in energy efficient housing for 10+ years, I have been heartened to see the start of proliferation of heat pump units. However, as a whole, the market seems to be flooded with units of as good quality as your normal store bought air conditioner. That is to say, as soon as something goes wrong with them, they are garbage.
How come we only talk about efficiency/environmental friendliness of use and not of the unit itself (and all it's embodied energy/cost)? If I save 60% on energy for heating every year but then require all the energy needed to build a new heat pump every 5-10 what am I really doing?
I would love to see an effort to create an open source heat pump itself, based off of COTS parts and raspberry pi or something similar where you are not locked out of the software and dependent on a supplier to have replacement parts that they probably stopped stocking 5 years after releasing the product.
I would be interested to see the math on replacing a cheap unit every 10 years versus an expensive unit that lasts 30. A few years ago, we replaced our 30 year old Carrier system with a new heat pump system that was relatively inexpensive. But here's the thing, the old system was not nearly as efficient from the beginning and it was much less efficient 30 years later. I'm not sure how much room for improvement there is with the new heat pump systems in regards to efficiency, but if the advances are significant every 10 years or so, it may net out to a positive.
Individually that's one way to look at it that makes sense. On mass scale though, if in 10 years someone can make one that's 50% better, it still behooves the world for the the units of today to last 50 years because even by then you won't have manufactured enough for everyone to have heat pump, let alone the most current one. Another way to think about it is imagine if instead of your unit dying in 10 years when you got a more efficient one you sold it to someone who didn't have one yet.
In general though, it's more the idealogy that gets me. It would be so easy to do a little more work to make things repairable, to use common parts, and ultimately create units that could last decades instead of lasting until an electric board has a short from dust or a pump predictably dies just outside of warranty, taking out an otherwise perfectly functional unit. It's just not viewed as the most profitable way, atleast not with how most people buy things today.
I think it could be profitable though, if you get enough people that can do the math and realize that over a lifetime it's cheaper than I think you could make that work. Additionally, it's not just about the cost over time but what happens when failures inevitably happen. Try having a repair done on any appliance today under warranty. First you have to go through the company and you get whoever they send and then you need their parts, if they are still available, which often they aren't. If the documentation on how to repair/maintain is opensource then you could potentially get anyone to fix it and if the components are COTS were possible then you aren't screwed when your 5 year old heat pump has an electrical failure because you can just but a new board (raspberry pi lets say) flash the software and install it.
> That is to say, as soon as something goes wrong with them, they are garbage.
Can you unpack what you mean by this? Standard A/C's can be repaired - fans can be replaced, as can compressor motors. Also, better and more efficient heat pumps can be more sensitive to maintenance (or lack thereof), because they often achieve that efficiency through finer control of mechanical components or lower resistance components.
IMO, a bigger factor in the longevity of traditional A/Cs is that they tend to have single-stage compressors that are over-sized for their loads most of the year, resulting in short-cycling and therefore shorter equipment life.
Just because something "can" be repaired doesn't mean it makes sense to. With most appliances if you are going to hire something to fix it outside of warranty it will cost hundreds of dollars at a minimum and you are often not guaranteed a repair will work. Even if it is in warranty, often a replacement part will be needed that is not available or is not economical to have a person install versus replacing the whole unit and the company will just scrap the whole thing and give you a replacement (after you've spent hours on phone calls, emails and talking to technicians).
The most egregious example of this I will highlight is electronics. Ask any manufacturer to provide a replacement board for an otherwise functional heat pump, air conditioner, etc. They likely won't have one. And even if they do, are you now going to hire someone to replace it? Do it yourself? If you aren't mechanically inclined its option one which can be hundreds of dollars and if its option two you will now be doing it likely with no or poor documentation spending how much of your time?
Heat pumps are no more sensitive to maintenance than air conditioners (besides the use of longer hoses for the refrigerant movement giving more opportunities to generate leaks). Or atleast their nature doesn't mean they inherently need to be (maybe that's the better way to put it). Compressors, fans, radiators, inverters, these are things that have been made for decades and if you walk into any commercial manufacturing space you'll find examples last for decades. That level of quality just isn't offered for homes.
You are absolutely correct that over-specifying heat pumps is also a big issue. That's kinda've a whole nother topic though that we could get into along with energy modeling, regualtions/practices, etc.
We have a decent-quality Mitsubishi unit that's 7 years now. Last year, one of the main boards died. Living in a country with strong consumer protection, I was able to argue my way into having Mitsubishi cover the cost of a new board, I just had to cover labour.
If I'd had to cover all the cost, it would have been more than 40% of the cost of a new unit, and then you start asking yourself if it's worth it.
Even though the marginal cost of the main board is likely below $50, the replacement ones sell for close to $500.
Hey - I've been following the steady stream of articles and discussion here about heat pumps, so I have a question that is tough to answer from the articles.
Is heatpump popularity regional? My understanding was that heat pumps are the technology behind residential AC, heating, and commercial HVAC. Thermodynamic 4 step cycle of a working fluid with expansion, compression etc. Every house I've lived in has had one. The cycle is reversed to cycle between heat and AC; dumping the heat to one side of the system or the other depending on need, as controlled by the thermostat.
What is the alternative? I've seen in (new and old!) England they use natural-gas radiators sometimes, and have no AC, or window AC units. Is that it, and now areas with those are switching more to heatpumps? Or is it new, more efficient heat pumps? Or do I have a misunderstanding of the existing tech?
The houses I've been through in the Midwestern US typically have forced-air natural-gas furnaces and cooling-only non-reversible central AC. Burning natural gas is way cheaper (ignoring externalities) to generate heat than even a heat pump, and can be easily scaled up to provide tons of heat on really cold winter days. Plus, modern heat pumps are high precision, complicated, expensive tech, a furnace is old tech: just a burner and a blower.
My natural gas cost is $0.82/CCF or $0.028/kWh. Electric is $0.161/kWh. That means a heat pump needs to be 575% efficient to break even on energy cost (assuming my furnace is 100% efficient, it's not, a lot of heat goes out the chimney).
People only get heat pumps here if they're carbon-conscious.
In my area in the midwest, nearly every house has a natural gas burning forced-air furnace for the winter and a standalone air conditioner for the summer.
Newer heat pumps have gotten a lot better, and as a result a few people are starting to use them here. Even so most heat pumps are the more expensive type that rely on geothermal coils. We have extreme seasonal temperature changes that make older heat pumps impractical. For about two weeks each winter, our overnight lows are around -20F (-29C) and we often see wind chills around -40. Summer temperatures regularly reach 100F (38C).
I would venture to guess that most residential heating in the world is provided by non-heat pump sources.
In many parts of the United States, my understanding is that it would either be natural gas fired furnaces with forced air, oil fired furnaces (with forced air? not sure), radiators (with water heated by gas or oil fired furnaces), or electric resistive heating elements (e.g. baseboard heaters).
UK is almost exclusively hot water radiators heated by natural gas boilers (or oil boilers in rural areas not on the gas grid).
There is a push by government to switch to electric heat pumps driving hot water into larger, cooler radiators (as this is more efficient for the heat pumps), backed by a £7500 grant for the pump and installation (with limited take-up).
Thanks for the info on this! It sounds like my experience has been biased by coincidence. Ie, I've only lived in a house that was wired for gas once! (Northern VA). My childhood home (Also northern VA), both places in North Carolina, and Florida have all been heat-pump based, with no gas line.
My apartment in the UK was even weirder: It had something called a "Economy 10", with an electric heater (resistance?) in a concrete slab under the floors that would run at night, then release heat slowly throughout the day. (No A/C)
In the US heat pumps have only seen widespread adoption in the last decade or so and even then mostly in new construction applications. Most houses still use either window or central AC units and then some other mechanism for heating, oil or gas furnace, electric baseboard, etc.
>If I save 60% on energy for heating every year but then require all the energy needed to build a new heat pump every 5-10 what am I really doing?
>As good quality as your normal store bought air conditioner. That is to say, as soon as something goes wrong with them, they are garbage.
Sounds like you're still saving 60% on energy because the status quo is also disposable appliances. It absolutely sounds better than nothing to me, but I am also hopeful for more maintainable and accessible heat pumps in the future. I haven't heard about any efforts for an open source heat pump, but I'm definitely interested in something like that myself
Where are you seeing this? Mini splits have been in use for a long time and just about all cheap brands are rebadged Gree and Midea, which are reliable and in use all over Asia.
IMO, the problem is that HVAC companies in the US overcharge so much for install/labor that homeowners are more inclined to replace them. They won't touch mini split brands that they don't install (and generally only install expensive brands)
Quality cones with design refinements learnt after the technology has been in people's homes for decades.
There is nothing theoretically unreliable about a heat pump - it would totally be possible to design it to work for 50+ years with just basic filter replacements.
Yup. Saving the world is going to be ruined by Chinese shovelware-quality equipment re-stickered with American brands, but in this case it's even worse since you're hiring a professional installer and those guys will only work with a short list of manufacturers, so getting somebody to install an expensive quality European model will be basically impossible (if they're even certified for use in North America).
China has been making lots of things for 50 years. Experience doesn't matter if North American "manufacturers" insist on importing only the the most disposable low-quality products.
Where I live every other house is heated by either air-to-air, air-to-water or soil-/ground-to-water heat pumps. -20C a large part of winter isn't uncommon, some places go even lower.
So to me it looks a little bit insane when people confidently claim that heat pumps are unfeasible in rather cold climate.
The best conditions for heat pumps are places with hard rock just below the soil, so you can drill a heat well and use it for heat storage during summer months, i.e. AC/cooling. In my opinion that's the main drawback with air- and soil-based heat pumps, can't recycle heat from cooling in the summer.
Is the kind of well that you'd typically drill for a single family dwelling capable of storing enough heat to make that worth it?
I know that underground heat storage is popular with district heating, where you've got a hollow mountain storing heat for the whole city, but the square-cube law means that there's a size below which it doesn't make sense. I had only assumed that that size was bigger than was feasible for a typical homeowner.
Don't need to use cooling to make it work, I live in a fairly large house without cooling and a bore down into the mountain below is good enough even though we have -15 to -25C for weeks during winter. It's in a small town so not an isolated location. Most people around here have air-to-water or air-to-air, because it's good enough and cheaper to install.
And it's not a hollow, it's a plastic ~1 decimeter pipe with ethanol going through stone some distance down from the surface. Not sure how long this collector is, but 70-200 meters is common depending on how large the house is and conditions in the ground.
Ethanol is an interesting choice... lower specific heat when compared with water. Is that to discourage things like tree roots from making a home in your well?
It's stable, cheap, carries heat OK enough, so it gets pumped through the pipe in the ground to collect heat and bring it back up to the heat pump.
If there's a leak it's bad since it's quite toxic to organic life. If you collect in soil rather than drilling into rock tree roots might push around the collector pipe a bit over the years but I've never heard about that being a problem.
Some (hopefully) constructive critics to make it even better:
- fix the left side menu, so that, even when the "Add fields" part is displayed, it can be scrolled up and down (because right now if I unfold "Add fields" and further unfold some of the items inside it, the content becomes hidden below the bottom border of the screen)
- add noise level information (the noise level of the compressor), in dB. Some manufacturers don't provide this info, so it would be really useful to gather it here.
Noise level seems huge. I don't have one, but every place I've stayed that has one the noise they make drives me insane. I would be really trepidatious about installing one in my place for this reason.
This guy[0] has done quite a few deep dives on heat pumps that cover a lot of the myths (eg they don't work in the cold). It's pretty interesting material if you're thinking about a heat pump.
It has always seemed silly to me that we spend money to keep a box of cold (fridge) inside the houses we're spending money to heat in the winter and spend a lot of money to heat up dryers, stoves, etc in the houses we're spending money to cool in the summer.
Watching these videos made me think there's a real possibility at some point to have something like a whole home heat pump that just moves heat from where it is to where you want it and in the process reduces the need for systems working against each other to heat/cool specific parts of the house. I understand there's something in commercial settings that has this capability but I'm blanking on the name.
My parents have always had an "outdoor fridge" that is a stainless steel equipment box that my dad salvaged from the junk pile at work. They put food in there that is less prone to spoiling, and use it through the fall/winter/spring months.
If I make a big pot of soup in the winter I will cool it down outside before putting it in the fridge. That way it gets down below the zone where bacteria grow much faster than if it were inside.
From an energy perspective it would be better to put it in the fridge so the heat would be removed by the fridge and stay in the house rather than dissipated outside but as far as I know the heat would also end up in the other goods in the fridge causing potential spoilage. It would be nice to have some kind of remote chiller pot hooked to a heat pump that would just pump the heat out of the soup and into a cold room.
The fastest way to cool it is to put the pan in a sink with cold water. But since that water is probably freshly tapped and thus cold, you're not really regaining heat, but rather warming the outside (if you then flush it).
But I find fridges are pretty good at what they do. If it fits, you can put it in the freezer for half an hour first.
If you're interested in installing heat pumps, there is a similar open data initiative started by some redditors to aggregate heat pump pricing quotes.
Really shocked at those prices, I really don't understand what's going on in the US/Canada. I could get a 7kW Mitsubishi Electric single-head mini-split installed with change for AU$3000 here (US$1950) if I buy the unit online and get one of the many, many installers around to put it in (fairly simple install if it's near an external wall is around AU$750 at the moment), but that document has prices in the $7K to $12K for that size?!?
Which is why mini splits are not very popular here. The install ends up costing so much. Labor is not cheap in US/Canada, and install is a lot of labor. Still seems like it should be cheaper though.
They're only 3.5kW units, but they seem to be the sweet spot of mini-split systems locally.
I recently paid 325 euros (about $350) for a unit and 200 euros (about $215) for installation. They are cheap Chinese units but the quality is good in terms of performance. This year they might be even cheaper.
I paid 15k CAD for 2 Daikin units two years ago, the pricing is kinda stupid but it depends on the quality of the model. Chinese models are way cheaper than Japanese models.
Heat pump technology is certainly out of the "early adopters" phase. It is basically the standard for new buildings in Europe (at least Northern Europe, I'm not sure about the South), and has been for years.
In Germany, where I currently live, they recently passed a law that constrains what kind of heating system you're allowed to put into your house to a point where basically only a heat pump fulfills all criteria (perhaps with the exception of pellet heaters).
I recently had to get a replacement heat pump. In the process I discovered that the EU has a database of energy ratings for almost (actually?) all electric appliances sold in the eu. This includes heat pumps.
I scraped the heat pump data and am the proud owner of 100% of this information. What I found is that some of the available data is inaccurate and much of the energy ratings (A-G character rating) is inconsistent with the performance of the device, probably due to changing standards over the years. It’s nice to see initiatives like this which hopefully will provide better and more normalized data.
As a side note. Air-to-air heat pumps have, as most people know, two parts to it. The indoor unit, and the outdoor unit. Many models can be used interchangeably, so the domain of heat pumps is a bit more complicated than I first anticipated.
Indeed. The data available includes most of the things you would expect, but some of it is just wrong. I’m only at my computer now, so don’t have a concrete example, but some models had vastly higher values for some fields than is possible.
I have a new NIBE pump (S735) that replaced my old, also NIBE (Fighter 640P) pump. It's a bit more silent than the older one usually, but sometimes it starts what sounds like a jet engine which is pretty loud. I can hear it from upstairs, far away from the pump, coming from the vents. I am not sure what it's doing when it makes that noise but it made me a bit upset with it, as initially I had hoped for a quieter house, and the pump was pretty expensive!
+1 yes we need a way to export and analyze data to get the insights we want. Would be great if we can share through Datasette which is tailor made for such applications
The heatpump performance data looks crowd sourced. If the website and DB are run with open source software, that's a different thing and seems secondary.
Just got a Daikin heat pump installed this past winter. Electric furnace is still used as a secondary heat source. Will have to compare more data over the last 12 months, but so far, power usage is way down.
I can also integrate home assistant with the Daikin which can control all of the functions and it's also able to retrieve a lot of useful data that you can use for adjusting furnace and heat pump parameters. I can get credit from the power company during peak usage times and I'm able to have home assistant interface with the heat pump to maximize those credits as well. Very happy with the setup so far.
I love my ground-source heatpump. I did the entire install myself, submerging the loop in the pond by my house. We get a COP of approx 3.0 in the middle of winter when its -25C air temp outside :)
I only used it for air-to-air heatpumps (or air conditioners as they are sometimes called). He the data is oretty good. I can't say anything about the other types of heatpumps but I've found the database quite useful.
> so we can see where in the world heat pumps are most effective.
They're not efficient when the temperature drops below a certain point. This is predictable and based on system design criteria. It doesn't mean it's not effective, it's just that it wouldn't be a reliable source of heating year round. It may still make a worthwhile addition to another system, or combined with several other upgrades, may become an acceptable single solution.
You've summed my points exactly while missing the major one. You don't need monitoring to determine any of this. You can just look at the construction of the building and the weather charts and you're done with the "will a heat pump be effective?" question.
Sort of. My house is 100 years old and was built without insulation (some rooms were insulated through remodels over the years). It uses water circulation and cast iron radiators and stays comfortable with my ancient cast iron boiler and 180°F water.
To know whether a heat pump (air-to-water) can replace that boiler effectively and maintain comfort, I had to find out whether the house would be comfortable with water temps of 135°F or so. Is there an amount of “that’s just looking at the building construction” to make that analysis? I think maybe technically yes, but practically no.
As it was, to get an answer, I abused my old boiler by turning the water temps down (causing condensation and slow damage [planning to replace it anyway]) and seeing what happened on cold days.
Don’t you want to replace the radiators with large vertical floor to ceiling radiators to get the same amount of heat transfer at a lowest possible temperature?
I am not familiar with the nuances, but this appears to be an equation with two variables - water temperature and radiator surface area. Maximising surface area should slow you to use lower water temperature. And the lower the water temperature, the more efficient the heat pump will be?
You didnt need to do that, though. It peobably wouldve been easier to use manual j (or some software) to estimate the heat loads in the house, with given set points, using weather station data.
I can find/closely estimate the heat loss easily. What is much harder to find is the heat gain/transfer into the room from 1920s cast iron radiators at 135°F flow and the balance of the system flow temperatures at those 45°F lower flow temps than originally designed.
Then, because the answer is almost always going to be "yeah, it's going to be really close...", I felt well-advised to prove it via experimentation rather than commit to changing the heating plant to a system that could not provide 150°F flow temperature.
The question is not about the general hydronic heating formula [nor manual J heat loss estimations], but rather "what will the delta T of the rad in this particular room, in this piping network [it's a converted gravity feed system, now being a pumped], using 69°F room temp and 135°F leaving water temp from the heat source?"
This is going to be a complex problem because of the shape of the radiator and you'll need to calculate radiative and convective components of heat transfer i.e. you'll need finite element analysis to do this. If you simplify it to a simple shape like a rod or slab you can get somewhere in a calculation, but this is only going to give an instantaneous measure because of heat transfer to the rest of the universe.
Alternately, to get a realistic measure, you'll need to set your boundary conditions about what the heat flow out of the room will be, which is a bit simpler to setup with U-values, area, delta-T, and heat capacity of materials. You'll also need to do this to every other room in the building simultaneously. This is a Manual J, or heat balance method or the radiant time series method load calculation that will balance out with the amount of heat leaving your radiator without knowing its specific shape.
For the, for lack of a better word, standard radiators there is a formula with a dT^4. But I totally agree, this isnt all that straighforward, given that for the dozons of installers, experts and home owners I have spoken, Ive heard dozens+1 methods for estimating. Estimating heat loss from a given building and estimating power output of a given installation of radiators, very few people seem to be able to calculate that.
If your heater can go low (mine bottoms out at 50 unfortunately), by far the easiest is to just test.
From the Mechanical Engineering/Thermodynamic angle:
> Ultimately, I proved to myself that a heat pump could work down to an outside air temp of about 18°F [which is slightly above our 99th percentile design temp] with flow temps of 135°F, so an air source heat pump could work with slightly reduced comfort on about 2% of days or could work all the time with supplementation with a 9kW [30K BTU/hr] electric boiler.
From the commercial angle:
> What killed the project is no heat pump installer was interested in doing the work (as reflected by outright declining to bid, while bidding a 4-hour gas boiler swap, or by bidding so high that they might as well not have bid, while also cheerfully bidding a 4-hour gas boiler swap). So my house still burns gas for heat.
On the engineering front: I think the answer is often going to "<hissing inhale> It's going to be close; we should probably test it..."
Thanks for the response. My feeling is that maybe in about 10 years Air-to-water Heat pumps will be more common in the US and we might have a better chance of getting a reasonable installation quote
Yeah no. It's become a bit of a hobby of mine, heatpumps. If I ask 5 experts/installers to take a look at a building I'll get 6 estimates, varying wildly. Plus, installers are still consistently over dimensioning and thus killing your sCOP, because they don't want customers to complain 'its slow to heat' and so on.
Calculating the heat loss of a house is really not trivial. Often you'll have no idea of the materials used or the quality of installation, and not really a way of finding out unless your up for some destructive investigation.
Heat pumps are reliable even in unfavorable conditions.
You will have to invest a lot more electrical energy and you might not be pumping heat as much as just converting electrical energy to heat, but let's not spread the myth that a heat pump will leave you freezing once outside temperatures drops below a certain threshold.
> let's not spread the myth that a heat pump will leave you freezing once outside temperatures drops below a certain threshold.
That is not a myth - I have a heatpump in my house and it will leave me freezing on the coldest days. The system is sized so that it cannot keep my house warm at -5C (the system can deliver heat, but the house will cool down). Worse, it did get below -25C here for a couple days which is as cold as any heat pump will work - I don't know of any house that is insulated so well as to be warm when the outside temperature is below -25C for a few days without some heat - but mine isn't one.
A correctly sized heat pump can keep your house warm to -25C, but if the installer doesn't give you a correctly sized system it will not. Most installers don't know how to size heat pumps.
A heat pump without a resistive heating /option/ will absolutely cease working below a certain temperature. They do, for whatever reason, sell systems that way in some regions.
That's true. Strictly speaking a heat pump doesn't need a resistive heating element, but I've never heard of units not containing that feature. After all it's dirt cheap and enables the reliability, we're discussing here.
Real question is does it prevent freezing? Like 100%. After all, the human body is quite resilient … above freezing.
I am thinking in Nome, Alaska where such heat pump could prove its versatility as an anti-freezing component of living quarters or even maintenance shed.
Humans can put on clothing and be fine in very cold temperatures. However pipes cannot 1C is a hard minimum safe temperature, once it gets colder than that you risk pipes breaking.
Perhaps, instead of spreading FUD, it would be worthwhile to mention these "certain temperatures", so that people can make an educated decision of whether it applies to them at all.
I'm looking at the datasheet for my Fujitsu system and it is specified to work down to -25°C.
Does it lose efficiency when it's cold outside? Sure. But guess what, it's still more effective than resistive heating! I am starting from a SCOP of 4.89.
The UNIT is specified to work down to -25. The SYSTEM includes the building it is installed in: the local climate, the size and heat loss of the building, how the install was done, and likely some other factors I'm not aware of. If you get less heat from the unit than you lose via other means the system isn't working even though it is delivering heat.
Perhaps you should have read my comments more carefully. There is absolutely zero "FUD" in any of them. I'm just pointing out facts. The primary fact is that you don't need historical data from heat pump installations to know if they'll be efficient in a given area or not.
They're devices. They're engineered. They have specifications. The specifications have implications as to how they will function in a given environment.
I'm not here to sell heat pumps or to make you feel good about your past purchases. Are you?
I think this could be Resolved by scale, but that’s precisely what the west is really bad at
If we standardised ground source heat pumps as a must have all multi dwelling developments like apartment blocks and rows of terraced houses who could share one well et cetera, It would not be a noticeable cost at all
Maybe, where are live there isn't much ground water and so no well can deliver enough water to be useful for a large building HVAC needs. There are a lot of ground source heat pumps around me, but they are all the coil in the ground style which doesn't scale the same way and so will be a lot more expensive to install.
It wasn't clear to me what kind of monitoring equipment is being used to gather this data, or whether it's just being manually gathered and reported by each system owner.
If the former, I'd like to get the generic equipment to use to monitor my heat pump system, and if the latter I wonder if the resulting inaccuracy results in improbable outliers like the system with 6.0 COP.
It would be nice (but potentially difficult) to add the sensible and latent capacity for heating and cooling given 3 design days: humid, hot, and cold. The btu ratings are useful to compare efficiencies but not sizing the system
How do these people monitor the heat output of the heatpump? Is that something you can get from the device itself?
I recently installed a Nibe S2125 in my house, it's been running great except I don't monitor electricity consumption of just the heat pump, nor do I know how to get the heating output.
I somehow doubt all these people have a specific electric meter on their heatpump, or do they? Mine runs on 400V and the meters are a bit expensive to get just for the data.
Are all the compared heat pumps working at the same temperature levels?
Otherwise, the COP isn't a good comparison metric, as even for an ideal heat pump with a COP = 1 / carnot_efficiency, it depends on the temperatures.
For instance, a heat pump lifting heat from 20°C to 100°C with a COP of "only" 2 is excellent, whereas lifting heat from 20°C to 30°C with a cop of 3 is not impressive.
A single COP is some yearly average usually but in these measurements it is probably a shorter period.
In europe there is a somewhat more rigorous measure of Seasonal COP (SCOP) where the typical climate (in my case nordic) is taken as a standardized test. So x number of days outside temp 0C, y -5C, z -10C, w +10C etc.
So in case of Air source heat pump if the outside temperature is +10 or +15 you can easily get COP numbers that are 9 or above.
Better technical documentation usually has rated COP for some different outside temperatures or even a graph.
Thanks! At the top of that webpage is a drop down to select the date-range; you can select a year (although there aren't that many entries) - and that is lower, I guess averaged over it.
note also, that the temperature difference is also influenced by the outlet temperature: if you have a radiator system, you'll need a higher outlet temperature than say a floor or ceiling heating system. this is because the energy transported is proportional to area of the delivery system. so that's also something to optimize. add in a decent insulation (less units of heat required to replace lost heat units) and you get a higher COP.
I'm surprised to see that basic things like heatpumps and insulation are apparently still controversial in 2024.
By law, houses in my neck of the woods are required to be well insulated, where the definition gets stricter every couple of years. Newly built houses have to be compliant. When renovating existing houses, efforts towards compliance have to be made up to a certain level. Every house that's sold or rented must advertise its energy consumption expressed in kW/m², and you can be damned sure that high energy loss results in severe impact on sales price.
Any kind of heater obviously has less work to do when heat loss is minimized by good insulation. Good options have been available for literally decades for most types of buildings.
The roof is typically the easiest, with many options. E.g. on the inside between the rafters. Or you can remove the tiles, insulate on the outside, add framing and retile. My roofer simply tore out the ancient roofing, slapped on some insulation, and finished things with EPDM. Easy peasy.
Floors can be tricky depending on the house and how much effort you're willing to put in. Easy if you have a crawlspace or basement, not so easy if not. I tore up and dug out the floors in my 100+ year old house and added 10cm of PIR insulation. This was not much fun, but after a hundred years the floor looked like shit anyway.
Walls have lots of options. Cavity walls can be filled with insulation by drilling a couple of holes and blowing it in. I insulated my brick walls on the outside, 12cm of XPS, with a layer of reinforcement, and finished with silicone plaster rendering.
Don't forget about the windows. Old windows are very leaky. Not just the glazing (double or triple for the win), but the framing is equally important. Also great for keeping out noise.
And then there's ventilation. I installed a forced air ventilation system with heat and moisture recovery. This had a bigger impact than expected, the indoor air is much nicer, and I don't lose any heat by having to open windows in the winter.
In all cases, of course, moisture has to be taken into account. You may or may not need a moisture barrier, some parts may have to be breathable, etc.
Over here, subsidies are available for most of these improvements, and our energy prices are high enough to make it worth the effort.
I pay under 200eur/year (not a typo) for heating, and most of that goes towards hot showers.
My neighbour has a heat pump and it's kind of annoying when running because the 180hz hum is audible in most of the rooms in my house. This in the UK and our houses are detached, but fairly closely spaced.
COP or CoP means co-efficient of performance. An electric heater has a CoP of 1. New heat pumps usually have a CoP of 4 or higher. My 11 year old heat pumps have a CoP of 3. This means they can produce 3 or 4 times as much heat as an electric heater, assuming the same amount of electricity, or produce the same amount of heat with 1/3 or 1/4 of the electricity.
At a CoP of 3, they are more efficient than electric heaters down to -15C. At a CoP of 4, down to -25C. There are better heat pumps coming with a CoP of 5.
What would make this even more useful (if possible) would be including 1) the UK equivalent of an ASHRE Manual J and 2) an ACH rating for the dwelling.
Heat pumps are great, but suffer from piss-poor installations and shitty salespeople. When I renovated my DC rowhouse, I talked to 6 different companies about the HVAC install. Only one, ONE, would do a Manual J. I had already done a Manual J myself (it's not hard at all) so I could compare their calculations to my own. They were slightly different (they calculated a greater load than I, but at the time, the insulation systems I used in the house were uncommon, so most of this difference was due to their lack of familiarity).
In the end, my rowhouse needed such a small unit (1.5T IIRC) that I couldn't get the SEER I wanted because no one makes high end units that small... I ended up slightly oversized at 2T, but that was necessary to get a unit from a good manufacturer (Lennox), rather than a pile of garbage flipper grade unit from someone like Goodrich.
What the heat pump industry is going to suffer from is the utter and blatant disregard to right-sizing units. The other 5 companies I talked to? They just walked around the house and then said shit like "This gonna need a 5T unit" and left.
Also, flex duct is bane of any central non-high velocity system. If an installer mentions flex duct for anything other than a short run to a register, run away from them. Flex duct is the sign of a lazy installer who is going to cut corners everywhere else they can, and especially where you can't see it.
In the same vein, if the installer doesn't have their own sheet metal shop, make damn sure they're buying your ductwork from a sheet metal shop and not from HomeDepot. One company I interviewed refused to do a Manual D (duct sizing) and said that a standard (i.e. we're going to get it at HomeDepot) 9x13 duct will be "plenty" for the return. The return (per the Manual D) ended up barely fitting in the chase alloted for it which is something like 30"x 24".
So be educated consumers:
- Do a Manual J and Manual D yourself, they're not hard
- Right size your unit. It should be running 90% of the time for max efficiency, so yeah, a smaller unit might take longer to cool or heat, but you shouldn't be turning the unit on or off but two or three times a year. A super high efficiency unit that is oversized is going to be terrible and inefficient. Don't fall for their shitty sales tactic of "but it's not going to be able to cool your house down as quickly as this 5T unit!".
- Demand good work. Like a plumber, never ever ever let an HVAC installer in your house unmonitored. I had to fight with my installers because they wanted to move a chase to the middle of the room "because it'll be easier for us". No, you have the plans, you quoted on the plans, so I don't give a shit that it's hard.
- Insulate and seal your duct work. You can't go back and do this, so make sure it's in your contract, and make sure they actually do it.
- Make sure you service your unit annually, it's a couple hundred bucks of peace of mind.
If you are willing to provide the installers name or any other details please reach out to my gmail in my profile, I am currently looking into this for my townhouse.
So i'm slightly mystified that we basically don't hear anything about fitting drainwater heat recovery [1], in which the lukewarm drain water from your shower is used to pre-warm the incoming cold water. It's extremely simple, pretty cheap, simple to fit, and can recover ~50% of the waste heat, of something which is tens of percent of the energy consumption of a household.
By all means, get a heat pump. But get a heat exchanger on your shower first!
[1] https://www.energy.gov/energysaver/drain-water-heat-recovery