That said, the efficiency gains on the energy consumption side are admirable. From a global warming standpoint however, heat pumps are actually still pretty bad because of the refrigerants.(https://www.drawdown.org/solutions/materials/refrigerant-man...) This is not an issue with more traditional electric heaters (resistive or otherwise).
The real calculus for those concerned with global warming (I understand this was not the topic of the writeup) is the net effect of these systems over their lifetime - aka, Energy Saved and its GHG effect via leveraging a heat pump vs the GHG effect from the release of the refrigerant. Perhaps the real win would be a refrigerant recovery business that is...air tight :)
Alternatively, Mitsubishi has been selling a first-generation product that uses CO2 as the refrigerant (the QUHZ model). It posts a COP of 3 for producing domestic hot water (that's pretty good) - I'm not sure why they don't post the COP for room heating, maybe it's not great. But I'm curious what the second-generation product will do!
These problems really aren't specific to CO2 hydronic systems, and also appear with HFC refrigerants when heating water. CO2 is actually very good for domestic hot water production, where the hot water is not returned.
The problem is really that hydronic heating is a bad fit for heat pumps in general. You'd much rather heat air, and skip the secondary fluid loop.
The plant had 6(?) pumps, each producing 18 MW heat while pulling 6 MW electricity (and also some district cooling). Not CO2 though, each pump had 9000 kg R134a as the working fluid.
Edit: I guess what I'm trying to say is that most of the radiator technology we use (like the in room part of the heating system) was designed with combustion-based heating in mind. Combustion based heating sort-of works just as well if the return water is 50C or 20C, but you would get a substantial boost in heat pump hydronic heating performance if you were to redesign heat exchangers to get as much temperature out of the fluid as possible. This is an optimization problem: as you increase the size of the heat exchanger, it gets more expense, but improves performance. There is an optimum in there somewhere...
In general, the evolution in district heating networks is towards lower temperatures, allowing better efficiencies with things like heat pumps. As you say, integrating heat pumps into existing district heating networks designed for combustion based heating is suboptimal, but redoing the network for lower temperature operation is incredibly expensive as well.
Currently, in the case referenced above, during the winter the heat pumps are AFAIU the "first leg" when the cold water returns to the plants; the output of the heat pumps is then routed via the fossil fueled CHP plants for topping up (depending on how cold it is, it's heated up to IIRC ~120C) before it's sent out in the network again. The challenge is that due to climate change, the fossil fuel plants need to be replaced with something else (no, biofuels are not an environmentally sensible solution). What that something else is, is not entirely clear. Moar heat pumps + wind + heat storage? Or geothermal? Or nuclear?
Sadly, I can find no third-party measurements of how well it performs in practice, so I guess it's still in the R&D phase. I did find a nice talk by Johnson about the project though.
You can buy small ones and play with them for very little money. They're used all over the place.
So I found the GAHP-W LB but the price seems to be a state secret.
Also the Lochinvar Optimus, but again, no prices.
But thank you - I don't understand why these types of units are not standard, are there downsides I'm not aware of?
Whenever this topic appears on HN I want to get on my soapbox and yell "INSULATION PEOPLE, INSULATION!". Most houses I've seen outside of the Nordics have shit-all insulation and that's depsite it working both ways - house stays cooler in the summer. It's such a small cost to add during construction and it pays off in a year or two, tops.
Modern, newly built houses in Sweden, way above the arctic circle, require less than 5000 kWh per year to heat and generate hotwater.
Classic market failure: operational costs don't factor into home buying decisions prominently, so whatever small added construction cost is borne by the homebuilders (the cost of added insulation doesn't quite result in an equal increase of selling price).
Short of instituting a carbon tax that would make operational costs of heating suddenly more prominent and priced accordingly, this is a great case for efficiency standards in homebuilding. Suppose your home came with an "energy star" HVAC rating...
Some states have even offered tax credits for doing so.
I'd love to install a ground heat pump but the installation requires digging up our fairly newly made garden. We'll move in a few years and buy something which has an A label with a pump and panels.
It also gives you an estimate of the amount Energy used to heat/cool your dwelling as well as the average yearly cost.
Obviously, this system is not perfect but its something.
Based on that you can work out if buying a cheaper and less insulated place is actually worth it or not.
You can argue all you want that it SHOULD be enough to share lifetime costs, but it doesn’t work. Just look at people who still buy incandescent light bulbs because they are cheaper at the cash register, even though they will save a multiple of the cost of the bulb over its lifetime.
We as consumers seem to ignore or discount future pain for lower prices now, which is why operating costs are ignored by average consumer if they mean higher upfront costs. And when marketers try to bring future savings into the present and get you thinking in terms of total cost of ownership, even the rational-types at HN cry "dark pattern!"
All of this is to say we haven't yet found how to make "it's cheaper to live in" an effective message.
Solar folks are getting there, though ("the system pays for itself in 5-7 years"), and with the rise of EV's, I think this reasoning will become more common.
The "dark pattern" complaint is that actual realized savings (tax credits) are mixed with hypothetical savings (future cost of gasoline) and taken off of the sales price. Meanwhile, things like delivery fees, sales taxes and maintenance cost differences are not added back in.
It's one part standard marketing, one part underhanded marketing imho.
> And when marketers try to bring future savings into the present and get you thinking in terms of total cost of ownership,
That's because it is fundamentally inaccurate, and therefor counter-productive. I'm all for demonstrating TCO differences, but when you show a "price" of $26k and the actual price is over $40k with taxes and everything added back in, suddenly you get struck with a bit of cognative dissonance.
Basically, moisture control and insulation is a tough problem. In modern houses the solution is to have an airtight layer of plastic sheeting between the insulation and drywall, but those houses should also have been designed from the ground up to have an active, mechanical ventilation system.
Based on experiences here in Finland, a lot of such buildings built in the 60's and 70's have developed severe problems, and frankly even new projects seem to have issues all the time. The more you insulate, the more you have to take care that moisture does not gather in the insulation because you no longer have airflow that would dry it out.
In a building that will be air conditioned, putting plastic sheeting between the insulation and drywall is a bad idea. The problem is that any moisture in the (comparatively warmer) insulation cavity will condense on the (comparatively cooler) plastic sheeting, wetting out the insulation and causing mold and rot. They also prevent the wall from drying to the inside.
It works fine in cold climates that are do not install air conditioning, as I assume is the case in Finland. In the majority of the US, even up to the Canadian border, many new houses have AC.
I can only hope 2x6 framing becomes more common, the subslab insulation has started to become code.
Based on your experiences what do you recommend? (or what sources do you recommend consulting to learn more about retrofitting older buildings?)
Counter-intuitively, air sealing is usually the #1 improvement. A good audit with thermal scans is worthwhile, especially if your muni offers a subsidized audit.
Tough to go into more detail without a little more information.
I think the hard thing for people to think about is that heat transfer is exponential. But we don't measure it that way. In fact R values are really misleading.
Meaning transfer coefficients can vary by orders of magnitude. So it's easy for one source like air leakage to totally swamp every other source.
 Figure of merit is really 1/R (smaller is better) not R.
> Tough to go into more detail without a little more information.
Have a ~1800 square foot single family Colonial located in Northeast USA built around 1910. It was partially renovated ~2000 but most of it's still uninsulated (afaict, still very new to this!).
Edit: e.g. googling brought up this article - https://www.architectsjournal.co.uk/buildings/airtightness-b...
People are grossed out by rodents and a leaky roof has to be addressed, but if their heating/cooling cost goes up slightly because a cable installer messed up are they going to hire someone to hook up a blower door, patch things up, and charge this back to the cable company?
There really is just a severe lack of building science education in American construction, because the margins are so thin and it is still dominated by blue collar "man in a van" companies. So you have boneheaded contractors drilling holes into air barriers because that's how it's always been done.
Heat conduction through studs in an insulated wall also carries sound. A 2x6 plate wall with 2x4 studs on alternating faces (think slalom) helps with both.
Fortunately this was part of a project to finish my home office, so I still had access to the space between the internal and external walls. Not only could I see the insulation damage, I could also repair it without too much effort.
But in general, I agree there's a responsibility gap when it comes to these installers. I think the best practical solution for now is to factor into such projects the cost of restoring a building's thermal envelope.
EDIT: I should mention that a blower-door test might not have detected this damage. The cavity whose insulation was damaged has pretty good draft-blockage from the rest of the house, due to fire-code requirements.
What, $5 for a tube of exterior grade caulk? Vapor barrier seal tape is 10 cents a foot. Add in $10 in labor per penetration and you're done.
You could leave it out of your estimate entirely and not even notice if your guys did the work.
edit: I'm a commericial construction estimator
I agree that restoring an air seal is trivial on a per-hole basis. My main point was restoring the lost insulation performance that comes from trashing one stud cavity of fiberglass batt insulation when the hole is made.
Based on my limited knowledge, I don't know what impact that might have on the overall structure's thermal efficiency. I would also worry about risk to any water-carrying pipes running through such a section in a cold climate.
In the Midwest there is an utter catastrophe where modern high efficiency houses are rotting away because construction and design errors let water in or water to condense with no way out.
We've only been hearing about how well Sweden and other Nordics do insulation, community heating, heat pumps etc for about 40 or 50 years. Various combined heat and power, insulation, passive houses etc would turn up on things like Tomorrow's World (60s-90s technology TV series) fairly often, like it was some sort of breakthrough new discovery. Well it was, to the UK, I guess.
"Hey, do you know why the English put their pipes on the outside of their houses?"
"It's so they can reach them easier to thaw them when they freeze!"
And then everyone laughs.
...and then you learn that it's not a joke, and then you cry.
Ventiliation is shit, one side never gets the sun so the outer wall is cold which means condensation is a daily battle, I basically run a big heavy duty dehumidifier from mid-autumn to mid-spring (at least its not a net loss, it dumbs a fair amount of heat as a byproduct so I can run the heaters less).
It's rented though so not something I can fix until I buy a property in a few years.
You can change out your furnace/AC/Heat Pump anytime, but try tearing off all the drywall in your entire house to replace the fiberglass insulation that doesn't work or was installed incorrectly. Spray Foam Insulation pays for itself and to think it's only around $3.00 a sq/ft at 3 " thick installed. People have no problem paying more for carpeting or tile floors, strange....
When it runs, you can never set it higher than 2 degrees F above the current temperature and if you do that when it's even close to freezing outside the unit will build up a think layer of ice around the casing...which just makes it spin constantly until we turn it off to go manually de-ice it. It's the most hated piece of equipment in my entire home.
Do you have a reference for one of these more effective modern heat pumps? I've been sincerely planning to install geothermal when this thing dies.
Heat pumps work best when you maintain a room at a stable, comfortable temperature.
Right, but for this to be economical, you need to have a well-insulated house, which is pretty much impossible to retrofit. So practically speaking, only newly build houses (and then, only those to the highest energy standards) should use heat pumps for heating. If we go around promoting them for other purposes, they will build up a reputation for being a crappy solution and people will shy away from them. That's my main problem with people promoting them - they often promote them for retrofits.
It is a complicated system -- lots of valves and reservoirs and so on, but very efficient and doesn't need much maintenance.
In a dense urban setting, you can heat homes with water heated at the local power plant, either fossil or nuclear. https://en.wikipedia.org/wiki/Cogeneration
I don’t think they’ve bothered to calculate the effects of pumping warmer water into everyone’s air conditioned home...
Here are some calculations suggesting that the numbers simply don't add up for ground-source heat pumps at urban population densities: https://www.withouthotair.com/c21/page_152.shtml
No need to muck around with fins in the sewage, or trying to convert to electricty, simply heating the incoming water a degree or two saves energy for your water heater.
In Norway most pumps are Toshiba and Mitsubishi. F.ex Mitsubishi FH35.
I'm joining you in that. I'm in Dubai at the moment thanks to airspace closure over Pakistan.
I noticed that richer Middle Eastern countries are the few places outside of the ex-USSR where foamed concrete picked up popularity as an insulation material. Seems to be a very popular choice for detached housing here.
I also noticed that despite the fabulous wealth, glass curtainwalls are not so widespread here. Even the most "skyscrapery" skyscrapers here have some solid walls and/or external shading (even Burj Khalifa on some levels.)
My exposure to the Nordics is limited but in the pictures I’ve seen there were lots of wood single family houses.
I think relative cost of timber is a bigger factor than you might think - the US has endless forests, while the UK came quite close to deforestation round about WW1 (earlier in Scotland). Traditional Scottish cottage construction had essentially only one structural timber piece - the roof beam. That was the most difficult part to source.
There is also a mentality of homes being forever. My house was built originally in 1870 and that's not particularly old. In the US old homes (except perhaps in a few stylish old areas) are something which need torn down and rebuilt.
I don't really understand where this belief arises from. Most homes in the US are built on undeveloped land. It's not typical to tear down an existing house to build a new one.
To the extent that it happens, it's generally because an area is essentially undergoing redevelopment. i.e. a rural area is being consumed by an urban city. In cases like that, the purpose is to increase density. It's pretty rare to tear down a single family home just to construct an equivalent but newer one on the property.
To the extent that teardowns are more common in the US than the UK, I imagine it's driven mostly by the ability to massively upgrade in the process. If you live in a 150-year-old stone house in the UK that's been updated over the years so that it's got modern electrical and plumbing and already maxes out your square footage (meterage?), what would you gain by tearing down except a lot more debt and some better insulation? With that said, I think this math generally doesn't work out for Americans, either, who generally trade up homes rather than rebuild.
If done right, it is likely the most durable material to use for siding. Will last for hundreds of years. Same with bricks if well maintained.
All other kinds of siding deteriorate quickly in comparison.
I am keeping an eye on the new cement siding that's now on the market, that's very interesting.
The British Geological Society lists "Significant Earthquakes since 1932" and there are twelve, but they're dated 1580, 1816, 1880, 1884, 1896, 1931, 1984, 1990, 2002, 2008, 1974, 1979. Three are offshore, three in the Scottish Highlands.
But wood in the UK was in demand by the Royal Navy, to the point where they depended on imported oak from the Baltics, forest cover in the (small) UK was down to 5% around the turn of 1900.
https://www.theguardian.com/travel/2013/jul/27/history-of-en... and a skim-read of the start of http://www.wou.edu/history/files/2015/08/Melby-Patrick.pdf
I wouldn't be surprised if the advantages of stone in the UK were/are availability until it became the default.
Mindful of how flames [Great Fire of London] had destroyed a third of the largely wooden city, building with timber frames was banned in the years after Sir Christopher Wren's 1667 Building Act. [..] until 1999
Ah, probably a lot of that involved.
On the west coast of Canada we'd probably never hit -20, but lots of other parts of the country do regularly.
In northern Sweden you can’t be surprised to see a month of -20 some years, so you probably want either a bigger heat pump, expect to use more direct electric in the pump (the heat pumps are air/water so the houses are heated with circulating water, not hot air) or something else entirely like geothermal.
Also worth mentioning is that Sweden pushes a lot of retrofitting of older houses, not just new ones. In the 90's, triple-pane windows became a legally mandated standard, so every old apartment building that only had double-pane windows had to add a third pane somehow, or change out all the windows or whatever.
A lot of older buildings are also adding extra insulation, one complex I used to live in that was built in the 1940's did that after I moved out. They stripped off all the outer layers to get to the brick, added foam insulation blocks, and redid the plaster finish.
When I lived there, the complex did the mandatory energy certification and got a shit score, so that's why they had to do it.
I do wonder how X's technology compares to existing household products, though.
Then he complains about the heating bill and blames me for it (because I cranked the heat when I came over for dinner one night). What a mystery.
p.s. even though the refrigerants are bad, still a mile better than the old oil heaters everybody used when I was a kid
I'm guessing here. I just know that the outside condenser and inside evaporator (in a cooling setup) need to match each other pretty well to avoid damage to the compressor or inefficient operation.
I'm sure there are heat pumps that don't cool well when the temperature is too high, but I don't think it's a general property of all of them.
For what size house, if I might ask?
Nitpick / clarification: this is not 'EPS' which is what is commonly known in the US a styrofoam (although according to Wikipedia, the trademarked name 'Styrofoam' actually referes to XPS); so not the white grainy stuff e.g. some disposable coffee cups are made from. Modern insulation is done with PIR, PUR or XPS.
What we really need are heat pumps which do not use HFC refrigerants - they are a pretty significant cause of global warming, and there are other options (CO2 being one of the best, in my opinion). https://www.drawdown.org/solutions/materials/refrigerant-man...
If you are going to replace your furnace or AC get a quote for replacing with a heat pump instead, either central or multiple mini-split heads. Heat pumps have gotten a lot better in recent years, particularly being able to work in cold weather down to 0F or below, expanding northward the places they are practical.
Gas units range in efficiency based on how much heat they recover from the exhaust, 80% is typical, 90+ for a condensing heater with two stage heat recovery. The problem with condensing is the exhaust gases fall below condensation point for the water vapor created during combustion requiring a condensate drain complicating the install location and cost significantly.
Heat pumps are over unity they use some energy to move more energy from the environment into the water, they are basically solar assisted resistance heaters.
The energy cost difference is not as clear when comparing a heat pump tank storage unit to a gas on demand tankless they are both typically more cost effective than tank storage electric or gas.
I have a 80% efficient tankless natural gas, it is wonderful having endless hot water at all faucets concurrently with a family of 4 plus occasional guests. I wanted to go condensing 90+ efficient but it was to complex based on its install location.
My previous water heater was a 70 gallon conventional electric. It didn't have quite enough hot water to get everyone through showering when we had extended family over, but it recovered reasonably quickly so that we only had ~ 30 minute gaps or so in waiting between the person who felt it get cold first and the next in line. Pretty reasonable.
Ours was about 20 years old and we also wanted a bunch of other plumbing work done, so we decided we may as well bite the bullet and get a new one. We replaced ours with an 80 gallon hybrid (electric + heatpump). We figured the extra 10 gallons would probably actually completely negate the need to wait between showers for those last people, so we were super stoked.
The reality is it exacerbated matters drastically. The refresh rate on our old water heater apparently was almost good enough to keep up with sustained usage between 7 people. The current one runs out of hot water out of 2 and takes well over an hour to even have enough hot water for a single next shower.
I tend to take pretty long showers in the morning - like 20 minutes or so. I use a CPAP and clean my mask, I brush my teeth, I brush my invisaligns (which is why I do my teeth in the shower - it's impossible to scrub invisalign braces and not fling infinite toothpaste flotsam everywhere), and I wash myself (which honestly is the fastest part - I keep my hair next to non existent and just do a body wash from head to toe, rinse, and leave. The point is that the 20 minutes I spend in the shower, with a low flow water reducing showerhead, still means my wife gets to get a cold shower an entire hour later.
However, from what I was told, there are new regulations regarding electric hot water heaters; namely, you can't get over 60 gallon tanks with a conventional hot water heater. Apparently people are getting around this by buying light industrial ones, which don't have this limitation. I wanted to try to cut down on energy usage AND I was keen on the idea of having a heat pump in my garage, transferring the heat in said garage into the water, thus leaving the garage cooler. It's like a really inefficient air conditioner for my garage, but given how hot that gets in the summer and how little I spend time in my woodworking shop, I wanted to leap at the chance to maybe make it a better environment.
All of this is a long winded way of saying it may win on efficiency, and it does have a number of compelling secondary features about it, but it also still suffers from poor refractory performance. If you have one as well - do you notice issues like this? Perhaps the one I got is faulty or just ... not good.
(Unfortunately it doesn't work well with certain plumbing layouts, and the rising price of copper has reduced the cost effectiveness)
So far so good - we do a bunch of baths/showers at bed time and no one runs out of hot water. Also - I'll add that we accidentally had the plumber remove all the low flow "plugs" from the showers so there's a lot of water flowing.
The pipe is pretty fun - not only is it fun to look at - but when someone is taking a shower it's fun to feel the heat at the top of the pipe and as you move down the pipe it gets colder until it reaches the temp of the cold water coming into the house.
Since it was new construction - we'll never know how much of a different the drainwater heat recovery pipe is making - but it is definitely doing work.
I can imagine these pipes becoming more popular (though rising prices will kill off any efficiencies real fast). Maybe code?
My plumbing layout actually might be darn near ideal for this. I'm not super keen on spending another thousand or so on getting it installed - at least not prior to the "planned but not scheduled" bathroom remodel, but that is at least worth considering when we do do the major remodel and complete bathroom reconfiguration. Our master bath is on the first floor and we don't have a finished basement so making something like this work should be comparatively easy. Thanks for the idea!
I'll have to pay attention into summer when it's like 95 in my garage. Maybe I can presume raging hot showers -for days- at that point :D
Speaking of which, does your model not have a resistive backup? Ours has several modes:
- only use heat pump, unless not safe to do so (ambient too cold)
- use heat pump normally but fall back to resistive to recover
- use resistive only
We only have 2 people in the house so we are able to leave it on the first mode, but in the second mode it would, presumably, be the same performance as our old resistive-only heater.
I also use a 1.5gpm low-flow showerhead (many "low-flow" heads are 2.5gpm).
Many manufactuers seem to offer warm and cold climate models. For example, pulling a random manufactuerer, Mitsubishi brands their cold climate line "Hyper" and specs out much better efficiency down to -13F temperatures.
Below 20F it puts out so so heat but can maintain.
Below 10F electric heat is needed from time to time to maintain.
Below 0F heat pump is worthless.
Edit: Wanted to add my is air heatpump, not ground source. Also reading other comments looks like heatpumps range from amazing to utter crap.
2. If it's not a coolant or compressor issue, you might need to replace it (either because it is undersized or end of life). Your local government or utility might have energy incentives for replacing it. There are also federal tax credit incentives .
My heat pump in Iowa worked just fine to keep the house comfortable down to 14F (the system automatically switched to backup heat colder than that). Something is wrong with your system if it can't do that. I couldn't begin to guess what though.
Insulation can be done to some extent — I've managed to insulate my 1930s house to a thermal resistance of R⒞ = 4,5 m²K/W in the attic and parts of the level above the ground storey, but this is not realistic for the ground floor — but it is not feasible to reach the R⒞ ≥ 6 m²K/W mandated for newly built houses.
The noise is a serious problem too. In terrace housing you simply can't expect everyone to install these things and maintain a sane level of quiet.
Better to solve this problem by insulating as much as possible, and to provide heat by collective solutions such as geothermal heat on a neighbourhood scale. The current 'let-the-citizens-solve-this-themselves' approach of our government is making homeowners insecure about what to do though.
As much I love TOH, I do wish they would take on more "budget" projects or at least talk a little bit about costs. But ATOH kind of fills that gap.
The concept of energy efficiency didn't really exist before the 1973 oil crisis as oil use per capita was steadily going up and up until then.
Energy Star, for example, was only established in 1992.
Energy efficiency is very very recent.
He does renos and new build in Austin, so mostly worries about keep heat out, but air tightness and insulation apply everywhere.
It provides heat (working great so far), hot water (but I already had an electric inline heater, so I can't speak to the slow-refill issues), and A/C in the summer. I'm curious to see how well the AC performs!
I also eventually want to swap out my electric stove with propane, though my last experience with induction stoves has me considering them too. Electric conduction stoves just aren't fun to cook on...
I'd love to convert the fireplace to run on hydrogen that I create myself via electrolysis one day (and have 0 emission tiki torches on the porch) but I'm not sure how safely I could pull that off! It's a bit of a moot point until I get solar installed anyways, since my power isn't coming from a clean source as it is.
Even here in western NY we occasionally have to deal with -10 F (-23 C) weather for a week and so that's a pretty big temperature delta if you want a comfortable 68 F (20 C).
Combine that with the fact that gas is still quite a bit cheaper per unit of energy than electricity (in my area) and a heat pump just doesn't make any sense.
The ability to have a single unit heat and cool is definitely nice, but without a geothermal-like ambient temperature to work with, I just don't see this working out, even with all the insulation in the world.
Of course in Sweden residential natural gas prices are almost 4 times what they are in the US so its a very different economic decision. Shows what a carbon tax can do.
Also, no one uses gas for heating in Sweden. Very old houses down town use it for cooking only.
We ended up having the compressor custom made by local fridge factory. Engineers there told us that designing such a small piston compressor and hoping it to be reliable and efficient is a futile effort, but they still did their best.
Is between piston driven compressors, and peltier coolers, is there just anything on the market? More quiet and robust than small piston compressors, and more efficient than peltier?
The factory and their tech level truly surprised me despite them being complete nonames, who mostly do fridge part kits for local production in 3rd world countries.
This reminded me yet another time of just how underappreciated are those no-name factories. They truly are the real unsung heroes of our globalisation era.
Body, piping, insulation, every other part came at less than that
I live in a temperate climate. I've sometimes wondered if it would be worthwhile to adjust house construction so that:
- In the summer, the kitchen refrigerator's heating coils touch outdoors air instead of indoors air.
- In the winter, the refrigerator's cooling is provided, at least partially, by the outside air.
- In the summer (only), the kitchen oven vents into the outdoors rather than into the kitchen.
- In the winter (only), a heat exchanger recovers some of the heat from our electric clothes dryer.
Why does a fridge need its own compressor that vents heat back to the house even in the summer?
Why can't your water heater use that same heat instead?
This all started because my brother used to redirect dryer air back into his apartment during the winter, using a saw dust sock to keep the lint contained.
I started thinking about how heat could be better managed if everything used a central ac/heat pump. heat generated by the fridge, your computer, the ac, etc could be used by your water heater, your heater heater, your dryer.
Add heat recovery systems to your dryer, and your drains, and bam super sustainability.
Once the water tank reaches its max temperature, then heat is dumped outside.
The practical problem is that you need to have the different parts work together, and fridge makers don't don't to hot water makers.
You don't need a fridge or a hot water heater or an ac or a furnace at that point, because the primary function has been offloaded to the central heat pump. you need heat exchanger attached to water, heat exchangers attached to a cold room, heat exchangers attached to a central air system.
You don't have to have the parts work together if the most expensive part of each appliance has been centralized. At that point you've now reduced the appliance to where to put the heat exchanger.
They are not connected at all. And this is in a building that is about ten years old.
I have no words, it's so fucking stupid.
There are also hot water heaters that, instead of burning something to heat water, have an heat exchanger on top of them to extract the warm from the surrounding air. Usually called "hybrid".
I known Rheem makes such units, but there may be others.
It won’t be anywhere near 100%, but the extra $50 in copper pipe could pay for itself.
I just hang my clothes and let the evaporating water cool the place a bit.
Right now it's mostly wasted heat, or IIUC even worse, in closed spaces it forces more energy consumption from the fridge.
Fridges for enclosed spaces should have a fan to push the air around.
The more space you give a radiating fridge, the more efficient it’ll be.
I do wonder if a small fan on a radiating fridge would pay for itself if controlled by temperature probes.
We have dual fuel, so we burn oil below 40F. Works great.
If you can afford it, putting in a heat pump that works off of ground will eventually pay for itself.
I'd say practical limits of current models are probably around -20C (-4F)
If you're interested here is an example datasheet of an air to water heat pump (2018) (using Celsius here):
Mitsubishi PUHZ-SHW112YAA Guaranteed operating range (outdoor): Heating: -28 to +21 Domestic hot water: -28 to +35
On page 108 you can find the actual co-efficient of performance (COP) for different outside temperatures and inside water heating temperatures. As an example: at -10 and an water temperature for heating at 25 you still get a COP of 3+. That means that 100% electricity moves 300% of heat into your house.
I have a ground-source pump and its brilliant. But plenty of my neighbours are happy enough with air-source pumps.
Mitsubishi and Fujitsu seem to have a large lead in cold-climate air-source heat pumps that are rated effective to -13F (anecdotal reports greenbuildingadvisor.com indicating effectiveness down to -20F). Yet, talking to builders, contractors, friends, and family, you will often still hear old tales about how "heat pumps aren't effective below 40F". Heat pumps come in a wide range of flavors. It's clearly possible to heat your house exclusively using an air-source heat pump in most USA climates.
Modern, high efficiency air source heat pumps can work well even below 0F.
Most of modern heat pumps (air to water) can work without issue all they way to -15/20* C.