Note that this thread is still active 13 years later! The most recent post is by the OP, and reads:
> I want to take a moment to recognize that the Homemade Heat Pump Manifesto has gone beyond 2 million page views. I would like to thank Daox and any other people who may have worked behind the scene to make it possible.
> My initial goal was to make available the knowledge and possibility that anybody with a few tools and gumption could convert discarded air conditioners, and dehumidifiers into very high efficiency heat ources, or cooling sources. Through the years, we have received reports of success from many people, living in many states, and countries.
> Another goal was to make zero money from this project, to give it away and to encourage others to take it, share it, sell it.
> In the beginning I thought that maybe 200 people would find this interesting. Obviously, I was wrong, gloriously wrong.
What I mean regarding Reddit is that you couldn’t have a thread running for 13 years like that, which you could easily follow (track up to which comment you’ve already read) and conveniently browse like on a forum. Pagination is important for that.
On web forums, a new comment on a thread automatically bumps that thread up to the top of the thread list, which means that even after a pause, existing threads gain traction like if they were new threads. (Possibly even more than new threads, due to the existing contents.) That way it’s easy to have a focused discussion for weeks/months/years on a particular subtopic.
But the problem with that approach is that people tend to revive zombie threads. I would estimate that <1% of threads actually have any useful discussion after 10 years, the rest is bumping zombie threads.
I’m not sure what qualifies as a zombie thread. If the new comments are meaningful contributions to the topic, it’s perfectly fine to revive an old thread. It’s certainly better than to have new threads about the same topic every few days or weeks, ignoring the previous discussions.
In any case, I’ve never experienced reviving old threads to be a significant issue, or to happen inappropriately to any significant degree.
I would just like to estimate that >99% of threads older than 10 years have useful information and the potential for useful discussion.
I realize that where i am enthusiastic about older things, cars/bikes/tech/languages, you probably like new stuff. I hope you realize that most of the zombie revivalists agree with me. Most of the time we are looking for a new solution to an old problem, which is the definition of progress. Locking threads after 6 months (thanks Reddit) or berating someone who want to revive an old topic, cripples progress.
One approach is to post an old, valuable thread (from Reddit or elsewhere) to HN, where annotated/appended conversation can continue indefinitely, especially if it reaches the HN front page for a one-time infusion of new readers and commenters.
What we need are search engines to offer an opt-in view or keyword which prioritizes this genre of valuable older evergrowing content. Perhaps Brave Goggles can be adapted to this purpose, using HN reposts and other signals of longevity.
Not my experience at all. I spent a whole lot of time on the endless sphere forum (forum for building PEVs) when I was in my teens and early 20s, and in my 30s now some of the technical threads from back then are still relevant and going strong. The discussion on there is light-years better than Reddit and HN for anything related to power electronics or EVs in general.
A simple visual indicator of the age of a post such as a zombie emoji (or something less tacky) is all that is needed to quickly disregard zombie posts you aren't interested in. Forums are great but we definitely need a UX overhaul incorporating the last 15 years of web UX research.
About UX, I agree insofar as web forums have worse usability than Usenet clients had before. However, I don’t see how web UX has improved in the last 15 years, in particular on the desktop, and in particular regarding forum and messaging apps.
I wish more people would do that. Reddit used to have that stupid 6 month limit on threads making it difficult to reply to someone saying something 4 years ago. They also need better tools to keep track of replies to older comments.
High-quality, long-lived threads could be renamed "Immortal", since they are periodically renewed with fresh content/life, while some older comments are still relevant.
A Reddit thread is automatically archived due to inactivity, forgot the exact duration. So in theory as long as somebody is posting a comment on a thread every few weeks (months?) it never archives unless the mods manually do it.
The problem with this is that adding comments to a thread does nothing to make it more visible. Traditional forms bump up all threads as long as they have recent activity, which Reddit doesn’t do.
The closest solution you could probably find would be for the mods to pin the post to the top, but in my experience most people just ignore pinned posts except in very specific cases.
That's not correct. On Reddit, thread archiving (on subreddits that haven't opted to keep threads open forever) is based on time elapsed since the thread was posted, regardless of how much activity there's been. IIRC the interval is 6 months.
Reddit Threads are locked after a while aren’t they?
Even if all of this would be in a Reddit thread I’d argue the usability of their site has declined to a point where using it for longer reading is unpleasant. (Login-Wall, collapsed threads, slow JavaScript frontend)
So yeah discoverable yes, but nobody would use it like that.
What? I've seen more recent threads getting "archived" (no one can comment or vote) earlier and earlier than ever. It used to be that every thread was guaranteed to stay communicable for at least a year, maybe 2. That was enough for most things but still represented a discontinuity in the transfer of knowledge as a new thread would need to be made and gain traction and votes and rarely (very rarely) the previous thread would be linked to avoid just recycling the same points and never making progress. That exceedingly rare linking now basically never happens and threads get archived as early as 6 months! I assume there's some variation as I believe I may have seen threads that don't get locked so early but it's a significant disruptor on the transfer of knowledge. And with how bad reddit's searching is, unless the previous thread is linked there's a tiny chance you'll ever find it let alone even know it existed.
That format just promotes reposting and restating the exact points that were popular 6 months ago. There have been many times I have had something to contribute to a discussion and have been rebuffed by the "This thread has been archived" popup. Truly any thread more than a year could not survive most current social conglomerates, I understand the scaling issues but it does not make it untrue.
sometimes whole subreddits get deleted because of $reasons. sometimes I get to a link and a message greets me: this subreddit has been deleted because of no moderation.
IMHO a bit of the problem with Reddit is that it's so extremely threaded. I can understand replying to an individual message within a discussion topic, but the tree growing to the right just makes it hard to find out what's the "latest".
The great thing about old style forums is that you'll check it once in a while and just go looking for the "latest" message, almost like joining IRC after a few days. You can go look at earlier messages but it's not always necessary.
Or am I wrong - can you make some sub-reddits work that way ?
It’s barely usable, for starters. Desperately trying to coerce me into downloading some mobile app. Riddled with ads and UI/UX anti-patterns. It looks more like a spyware site or a scam site than the modern “front page of the internet” they liken themselves as.
For the rare times I want to navigate to that cesspool I have to manually change the URL to “old” but it’s just a matter of time before they get rid of it.
Not to mention all the other issues that plague the site. Archived posts, dead links, deleted posts, deleted comments, deleted entire subreddits, and more. It’s not a place to effectively find older content much less truly old content. And worst of all the search function is comically useless so much so that there is practically zero self discovering within Reddit itself. You must exit Reddit and search on a search engine with “reddit” at the end of your query.
On a ten year old reddit thread you'll find the top voted answers and top voted replies to those answers but not a sequential discussion for page after page.
One thing I noticed when reading on diy hrvs in the past, is that many porjects are not taking into account air volume in the two ducts, and the amount of nominal flow for the size ducts compared to the ideal amount of air exchange. A 5 inch duct inside a 7 inch duct is more or less the correct size for many homes: about 50 cfm each direction. I do like the fact that there is a ton of dead space in most attics, where you can just drop a long, well insulated pipe hrv and be done with it for a relatively low cost.
One note of caution, he describes removing the lath and plaster and inserting eps insulation. It didn’t mention if he did this, he might have done, but it’s important to have a continuous taped vapour barrier on the warm side of the insulation to prevent water vapour from passing through, condensing on the timber structure and causing it to rot. Also ventilate the cold side of the insulation or a least have a gap to form a capillary break with the cold outside wall. I’ve seen a few badly done insulation jobs in timber buildings that have needed floor joists and studs cut out and replaced. It only takes about 15-20 years.
Be careful with an impermeable vapor barrier especially if adding one. It may work perfectly for keeping water out of the wall cavity in winter, but become the condensation layer in summer - on the wall side!
You can use smart vapor control layers (such as Intello) to counteract this - but be sure you’ve discussed how the wall can dry out if it gets wet.
And the worst of all is if you end up with two vapor barriers - one on the inside and one on the outside - you’ll end up with a “dirty diaper” effect.
Lath & plaster does not form a vapour barrier; deliberately not in most cases (there was perhaps some crossover when more moderm building techniques were still using lath and plaster) - old houses need to 'breathe' as they say, moisture needs to be allowed to move between inside and out. They can be warm & dry, but the way to achieve it is (paradoxically) porous materials.
Yes of course, but I was thinking more in terms of DIYers jamming a lot of non-breathable eps into old houses. Probably better to say consult someone who knows what they’re talking about before you internally insulate your old house.
Under my house ( 1920's wooden home ) I see EPS pushed up against the wooden floor boards. This was done by the previous owner. The EPS itself is exposed. Is this safe ?
> continuous taped vapour barrier on the warm side of the insulation
so what do you do when it is 100 degrees outside and 70 degrees inside during the summer, and 30 degrees outside and 70 degress inside during the winder? Move the vapour barrier?
I'm glad someone addressed this as I cringed visibly when I got to this part of the post. I'm very much hoping someone with actual experience with controlling moisture stopped this person before they completed this installation. If not, that house is the residential equivalent of a dead man walking.
But like it says on the page, because air source heat pumps have been getting a lot better they no longer sell the kits. There are a couple of individuals on YouTube who have used similar GSHP kits and had good success. The main challenge is that you need to dig 100ft of deep trenches per ton of cooling.
Edit: should be 300ft not 100
We just build a house on the west coast of Sweden and we initially considered both a ground or air heat pump. Essentially our builder said with modern houses and heatpumps going for the ground heat pump was really not worth it. Their efficiency gain only becomes significant at outside temperatures below 10 deg C and there were just not enough days of such low temperature. Instead it is better to invest that money into a solar installation.
As someone who's used air source heat pumps for years, they were good to around 5C, at which point they would start to ice up and need heat pumped out to melt the ice. They were utter crap if you had any kind of winter conditions.
I'd love to believe that modern ones are better, but its hard to pull the trigger on them after years of suffering.
I currently have oil heat, and love it. Nice hot (not luke warm) air. And if the power goes out, I just fire up a generator and I have good heat, because the blower doesn't take much to run. Having been w/o power for stretches as long as a week during winter, that is a massive benefit over electric heat.
Many modern heat pumps are much better than what you remember. Some maintain their full rated BTU output to 17F, or in the extreme models, 0-5F. They usually output some percentage of full BTU at even lower temps.
The common Asian 'mini split' models also use variable fan speeds to maintain higher coil temps and have output air that is warm enough to avoid the 'luke warm' issue of heat pump coils on 'dumb' air handlers that blow full speed.
That said, for cold environments, a backup is often required to make up for the performance drop at very cold temps without massively oversizing the system. Hopefully, you have your oil furnace coupled to a heat pump or perhaps supplemental minisplit heads. That is the best of all worlds: the HPs can cover 80-90% of the load, only needing the oil for extremes. Oil is likely to hit 5 a gallon this year, like last, so it would suck to rely entirely on it.
Yes - we have a dual fuel system. HP is used when the temps allow it. As far as I can tell, it's not eonomic to run it below 5C, and certainly not comfortable.
Similar in Lithuania, where buildings are required to be certified to A++ efficiency. Electric floor heating and air to air heat pump (aka split system) is enough. Solar panels are much better value. Cooling in summer is kinda becoming much bigger issue.
For older building even replacing wood furnace with air to water system is enough.
Ground heat pumps provide free cooling in the summer for a very limited amount of electricity as the ground will be at 10-15C (depending on where you live) so you don't need to use the compressor and just make the liquid flow to cool down your house.
It also has the extra benefit of heating up your ground for the winter period.
While that is in principle true, in practice there are quite a few issues. Many heatpumps here are made to heat the water for floor heating but don't transfer heat to air indoors. So you would cool using your floor which isn't very comfortable usually. More importantly because of the above the heat pumps are build for only one directional transfer. If one builds their own system it might make sense to plan for it, but even then it's unlikely that Sweden will become so hot that opening windows will not cool off the house enough. If it comes so far we likely have more pressing problems.
The ground heat pumps are not used in the opposite direction, it doesn't cool down water to the floor but it flows water at 10-15C into your floor. According to the installers I've talked to here in Belgium, all the ground heat pumps devices are capable of doing that.
While this might not be needed in Sweden, it's more interesting further south. I live in Belgium and we had a long heatwave this summer and they predict more of those in the coming years. So cheap efficient cooling might turn out useful here (even if nobody had AC systems 20 years ago)
Not to say you were wrong since in making that choice but with climate change days of extreme temperatures in both directions will become ever more common so so you may have considered it an investment into the future. Of course you may have other problems by then (a reliable source of food for example)
> (...) with climate change days of extreme temperatures in both directions (...)
This sort of take is unwise. It makes zero sense to invest today in domestic systems with the expectation that at some point in the future there will be extreme events a hand full of times throughout the year. The benefit of shaving a fraction of a percent from the baseline outweighs multipercent gains of hypothetical extreme events that happen a few times a year.
When building spend as much as you can on the building envelope (preventing air, vapor, water movement) and insulation.
Those cannot be easily changed at all, but you can relatively easily add another heating or cooling device.
And if you build above code minimums (you should!) be sure to have someone knowledgeable calculate the actual heating/cooling load. If you don’t, the HVAC contractor may assume code minimums and oversize the system.
Or get systems that are entirely variable.
And get every step inspected! Mid build blower door tests are a great thing to do (right after the air seal envelope is up).
> Spending money hoping to bank on the occurrence of unexpected outcomes simply can't be justified.
I would have agreed a decade ago, but in the one year our house has been standing, it has endured two 100 year events (a heat wave and a rain/windstorm).
We overpaid about $1000 to go one size up on the (variable) heat pump / AC and $10-20k to oversize + harden the solar / battery.
It has been worth every penny at this point; the solar kept the fridge, freezer and AC happy in > 100F heat during a power outage. That's $500-1000 of food just for the one event, and outages are increasing in frequency. (Air conditioning was mostly unheard of in this area 20 years ago, since it didn't get hot enough to ever run it.)
My big concern is that we're already eating into the engineeeing tolerances for the wind rating on the house itself.
I do agree that you should consider what can be upgraded later, and put money towards things that are hard to change (insulation, wind ratings, etc.)
the "it doesn't get hot enough to need air conditioning" argument was used to build out tons of apartment complexes in the pacific northwest, say, around Tacoma and Seattle. I lived in Tacoma in the mid-2000s for a summer and it was miserable. And everyone i spoke to about it said "yeah, that's the joke."
You are making assumptions that may be not true.
1. Those events will be a handful, I see no indication of that on the contrary
2. You can always upgrade later. You don't how a system can deal with extreme
and you don't that those things will be available later. Maybe they will, maybe they won't.
> The same can be said for most insurance products.
That's a terribly silly thing to say. Think about it for a second, particularly how insurance premiums compare to the cost of buying/rebuilding a new item.
The part with the compressor in it costs $12000-$15000 minimum just for the device, nevermind installation and the rest, and that's for an equivalent to 3-6 ton systems commonly installed.
My mini-split system worked fine down to about 10F, then it was defrosting for 10 minutes after every 8 minutes of use or so. I just turned on crypto miners on a few computers to supplement. Laptop crypto mining is useful if you want to keep your hands and wrists warm, hats, blankets, sweaters, and some old 100+ watt light bulbs will also help.
All this is to say "you can just get a -30 degree capable system" is out of reach for most people in the world. A large swath of people geographically close to my house still use window or wall HVAC units, rather than ducted systems. I was the only split ductless system my HVAC installer had ever installed - they had to come fix their install 4 times (four!) and eventually i contacted the asurion purchase protection people and got refunded for the cost of the HVAC system.
it works fine now, i told the HVAC installer to cut the threaded connectors off everything and sweat all the copper lines together, and it hasn't had an issue since.
it was always breaking in the late fall and early spring, where it had to heat at night but cool during the day, it would always break around 11AM. The pressure differentials must have been an afterthought in the design, i guess.
Here in Finland you can get a split system good for -30 Celsius for 2-3k€ including installation. Mitsubishi is considered the best, but others are available. My Panasonic has been working fine.
is that for a single head minisplit? In the US i installed one back in 2004 by myself, and i remember it costing around $1400.
the system i have now is also a minisplit, but it has 5 heads, and is 5.5 tons. If i run one of 4 heads by itself, it can do 3 tons to just that head. the fifth head is smaller BTU, i think it's 3/4 ton max. It cost $3,723.68, plus an additional $5000 to get it installed and working, give or take. As i mentioned, i got the $3723 refunded due to manufacturer's defect.
That's for single head, yes. From my point of view, single head is the norm here. In here too, I would imagine multi-head to be cheaper per head than single head.
This is a wonderful thread, thanks for sharing it here.
> "The kicker is, that the smallest I have been able to find is four ton (48,000 BTU/hr). So this means that in order to proceed with the project, I'll have to build my own heat pump. In HVAC, bigger is not better... just slightly smaller than big enough is best, economically speaking."
Is he saying here that a heat pump that's too large for a space is less efficient at heating, or is he just saying that a bigger one costs more to buy?
If it's the former, can anyone here tell me why that is? It's hard to Google since it gets mixed up with other info like "heat pumps are less efficient at very low temperatures" etc.
I would have thought they'd end up the same. The only reason I can think of is that a bigger one will maybe turn on and off more often to maintain temperature than a small one that's on all the time struggling to keep up.
The term of art is "short cycle". There's also the related "turndown ratio" which is just minimum_output/maximum_output. The discussion at [1] isn't bad, but [2] has a little diagram showing the cycling (in this case as a benefit of variable-rate inverters, but also as a warning).
I agree it’s hard to find reliable information in this - ASHPs and GSHPs are very hyped right now so a lot of the information that comes up in searches is quite low level or low quality. For example I’ve been told that a heat pump is at peak efficiency when it is sized for a duty cycle of 50% but asking why exactly this figure hasn’t yielded good answers.
As I understand it, it comes down to a couple of things.
Heat pumps are much more efficient when providing lower temperature flows, their efficiency drops off significantly where the delta between the heat source (air or ground) and their flow temperate is higher.
When an oversized heat pump cycles it is going to quickly reach a higher temperate and shut off where as a correctly sized unit will cycle for longer. So I guess simply it comes down to having the heat pump operate in the most efficient range for that property for longer vs. short spikes at temperature where it is less efficient.
Most heat pumps have a variable speed motors so they can modulate their output to match a desired flow temperature but this only operates within a range relative to the size of the unit. So if the unit isn’t correctly sized for the required heat output to be in its range then it has no choice but to cycle inefficiently.
I don't think it's the temperature delta in this case, at least not between the room and outside. I suspect internal equilibration of the unit when power cycled and also energy transfer design capacity on the indoor side of the unit are to blame.
> Most of the consumer advice is very low level - this Heat Geeks site seems better that most, but it still lacks enough detail for me to get into the numbers
You'll probably want an undergraduate physical chemistry textbook for this.
Thanks. Yeah, especially difficult when you read multiple different claims and none have a source. They probably heard it themselves from someone else.
I'm quite curious because I have an old-ish heat pump that's a little small for the space and I've been thinking of getting a larger one. But if it'll be less efficient then maybe I won't. The one I have does perfectly fine except on a few of the coldest winter mornings.
800 watt for the refrigerant pump, and about 100 watt combined for the two fans.
This means even when I'd like it a little warmer on the coldest days, making the heat pump use more power isn't an option.
A larger unit would have a bigger refrigerant pump and larger fans. This would result in us inadvertently leaving the unit on a higher heat setting more often.
Also, a larger unit will be turning a larger pump and larger fans even when smaller would achieve the same outcomes. Mechanic losses.
These two factors, human habit & mechanical losses, are, as I understand it, why you're generally better off having more small systems than one big system.
We have three split systems, in addition to the 7kW unit at one end of the house, there are two 2.4kW units, one I'm each of the bedrooms we use. When one or more units aren't required they can be turned off. Another advantage of this setup is that it's extremely unlikely all three systems will breakdown simultaneously.
Another issue with the larger units is they tend to be ducted, where the ducting is in a poorly insulated roof space, so there's additional heat losses there, and additional losses due to energy required to push air through the ducts.
Your first point is a bit silly: get a smart thermostat and it’ll take care of that for you.
Your second argument is silly: a larger pump will surely take more energy to run but will run for less time. It’ll also wear out slower as it doesn’t have to work as hard unless you have drafts and it has to cycle on and off all the time. Generally having more capacity is always a good thing for mechanical things.
> if you have a large compressor, you pay more for it with every revolution the trick is to figure the maximum BTUs or watts you will need, and design a little bit smaller. Plan to use a supplimental energy source to fill in during extreme conditions.
Worth noting the AC_Hacker paid $25 for the AC he used for this.
I think it takes a while for the juices to equalise and reach equilibrium before it’s running at max efficiency. You don’t want a duty cycle of say 15mins. You want say 1.5hrs. Something like that. (Numbers very hand wavy this is not my field directly) With an over designed system it stops and starts too quickly and this invalidates the warranty on commercial systems.
Modern heat pumps drive the VFD and circulation pumps as needed (i.e. the pumps run slower when the heat demand is low).
The main factor for good efficiency is low output temperature- underfloor heating works at ~35 deg C, radiators work at ~55 degC (because of smaller surface area).
I sized my heat pump based on historical data of heating oil /diesel consumption- since I had the data of past two winters, I could reliably determine the maximum continuous heat requirements for my house.
It also makes the environment itself uncomfortable in many cases - excessively drying the air, or causing weird moisture/condensation issues (as it won’t fully cycle the air in the house before stopping).
Essentially, you want your HVAC system to run for long enough it’s a gradual transition in temperatures inside and the equipment can run for awhile each time it needs to run to avoid the start/stop problems and let it ‘settle in’.
Brine temperature varies over the heating season by up to 10 deg C.
I really tried to verify the horizontal coil length and installation depth recommended by installers from the first principles, but I had to give up, as there were just too many unknown inputs: the type of soil (thus, specific heat and heat conduction), water content (which varies over the year), received solar energy (shady/sunny).
I am currently installing a Thermia Calibra ground source heat pump (installers are apparently too busy).
When I looked at the insides of the pump, the simplicity of construction was surprising- I could readily understand whats going on, as it consisted of off-the shelf parts made by other companies- compressor, circulation pumps, VFD and heat exchangers.
I second to that. Just got same model installed few weeks ago and was having exact same thoughts. However, now I start to think that devil is in the details (as always). And it has ton of details, which probably have cost thousands on people hours to design, test and implement. Most are related to how to make it work with maximum efficiency while consuming as little power as possible, some are safety related, etc etc. And the build quality is outstanding, it works flawlessly so far, no complaints. Despite the steep price, one of the best investments I have made recently.
Yeah, I have travelled that road too often (hmm, looks simple, I bet I can make it for half the cost- and a year later I have spent way more even disregarding the cost of my time and still only have a barely working thing) to know how that would turn out :)
Ah, the vive of people on the Internet talking for over a decade on an old phpBB forum thread...
A bit off topic, but I really think the existing forum sites aren't really that incompatible with "younger" people, and might have a renaissance later on (looking at how they are using Discord in a similar manner!) It's just that these old forum sites have lots of UI clunkiness that deter people from browsing or joining the site (older people who kind up grew up with phpBB might be accustomed to these sorts of jank, but you shouldn't expect someone who weren't in that era to be accustomed to it.)
I still use a couple of them for niche interests. The one thing that annoys me is that they still make uploading photos a chore. Usually you have to resize the image your self to get under some pathetic size limit. It's enough that people tend towards text when a picture or a drawing would be much better.
When you're a guy running a long lived online community on a $100 a year VPS you avoid storing media as mush as possible. There's a reason photo bucket sites used to be so popular.
To aid the discussion: There are multiple kinds of heat pumps used for homes, mainly air-to-water and water-to-water. Since the post is 12 years old, the availability of air-to-water solutions may be understated. At least in Europe it is now quite common to find them in front of new homes. Placed and looks like an AC unit, sounds like a laptop from 2005.
I get that if your heart is set on having a heat pump you need a heat pump, and that's the end of all financial consideration.
But how does, say, $10K of heat pump compare to $10K of insulation and better windows/doors/roof, or $10K of solar panels and cheap ultra-low-tech repairable all-electric HVAC, or $10K of some other form of physical investment I'm not aware of?
If you have a perfectly serviceable means of heating that you are happy with, then it's a straightforward cost analysis (cost of consumables for the current heating method vs cost of electricity for the heat pump).
I can only give an example that applies to my situation: previously I burned ~2300l of diesel which cost around 2300EUR for the previous heating season. So the yearly energy consumption is about 24MWh (combustion heat of fuel multiplied by efficiency of the furnace of ~94%).
If I were to install air source heat pump, it would require about 8-9.6MWh (COP =2.5-3) of electricity per year (4000-4800EUR at the current fixed price offering from my electricity supplier of ~500EUR/MWh).
If I were to install a ground source heat pump (COP of 4.5-5.5), expected electricity consumption is between 4.3-5.3 MWh or ~2200-2600EUR/yr.
If I were to power the ground source heat pump using the electricity generated by my solar panels (Latvia currently has 1:1 net billing system, but there is a grid cost of ~50EUR/MWh) the expected yearly heating cost is ~210-260EUR.
At the previous electricity cost of ~100EUR/MWh, air source heat pumps for not-so-well insulated houses might be attractive option- but not at the current prices in Europe.
When I did the calculations this spring, the break even time for heat pump + solar installation was ~8 years (based on fuel and electricity costs at that time).
Right now it's around 4 years (and I might even get ~40% of the investment from a government clean energy incentive programme). However, I have to operate under assumption that a crazy dictator of a neighboring country doesn't decide to invade and wipe my house off the Earth...
Insulation almost always wins during initial construction.
Solar panels probably come in second because they create waste energy that unlocks free EV charging, etc, etc (but you will pay more than $10K for the system), so, thanks to sunk costs, other stuff becomes "free".
Heat pumps are probably the cheapest big bang for the buck upgrade for existing construction (especially if you have to replace your HVAC anyway). Minisplits are often a big win for retrofits of buildings without central air.
All of these things are dominated by labor costs, and we are in the middle of a labor shortage. You are unlikely to find realistic financials unless you get bids and compare with your personal energy rates.
We didn't do any of that.
We just assumed energy prices would continue to explode over time (we were right), and jumped off the inflation carousel by putting in solar and all electric appliances.
Also, we can't get natural gas service, and propane costs 4x per BTU more than natural gas around here. Most electrical appliance upgrades are subsided by the government to make them competitive with natural gas.
That made it a no brainer.
Since then, a bunch of indoor air pollution research showed that natural gas causes asthma, etc, etc. Also, the war in Ukraine started.
So, what are your health, future financial predictability, and engineering economics braincells worth? For us, the answer was "less than the installation cost of the system".
Also, after all they put us through, seeing a -$120 bill from PG&E each month makes me irrationally unhappy. ;-)
A heat pump is 3x more efficient at heating than a resistive electric heater, making it just about a wash with a gas furnace in most markets in terms of sustained cost. The hardware is more expensive, but not THAT much more expensive. When you include installation costs and amortize over a 20 year system life, the overhead is non-zero but quite low (10% or so). If you guess that gas is going to be more expensive in the coming decades where electricity is futureproof, it seems like a good bet to me. Ask me in 20 years.
Lived & owned homes for 20 years in an area where ASHP are standard installs as the climate range meant 100% of normal (outside of freak polar vortex) heating and cooling was covered by the heat pump. Inexpensive part failure is common annually - usually capacitors and fan motors. Usually expensive part or system failures occur around 10-15 years.
I have zero knowledge about the topic but I wonder how NA specific is this thing? As far as I’m aware houses built with thin wood walls are more prevalent there, like in the original example. I live in a similar aged house (maybe a bit older) in Europe but we have 1 meter thick stone walls. We don’t have AC or ceiling fan but house always keeps cold in the summer and warm in the winter. I like the topic but curious how would that work with stone wall houses, especially like my example old style ones with thick walls
Stone walls are terrible for heat insolation. They have inertia but no insolation. So they are good in the Mediterranean coast where you want inertia in summer as some sort of natural climate control to keep it cool during the day. But they are terrible in winter when what you want is insolation to keep the heat in during months.
A 1m stone wall doesn't even insolate as good than 5cm of dedicated insolation panels. It happens very frequently now that old houses are renovated by adding insolation to those old stone walls, but of course you lose the charm of stone on one side of the wall.
This is why you have basically no stone houses in Scandinavia, because in winter it would just be impossible to heat.
Stone houses (in the modern times they're made from concrete or brick, sometimes with insulation) exist in Scandinavia and they have good insulating properties. A modern stone house is even better than stick built houses when it comes to insulation.
insolation is not insulation. Insolation comes from the sun. You want stuff that rejects insolation for the summer, and you want stuff that allows the sun to heat the mass of the house in the winter.
Indeed, that seems absolutely insane. Like a castle that would need to survive some sort of siege. Land is expensive where I am and I cannot imagine wasting that much on such insanely thick walls.
I want a picture. Walking through the front door must feel like going through a tunnel.
I’ve seen some that are basically build as two concrete block or brick walls, and the center are was filled with rubble stone and dirt.
This is similar to an “earth house” and is very comfortable where the average (or basement) temperature is comfortable. The walls make an insane amount of thermal mass and the temperature inside changes very slowly.
It's not insane. I currently live in a house where some older rooms have 0.9 meter adobe brick walls. These were built in mid-XX century, when this was normal. Now we have better materials and don't need that much width.
When you are building your most expensive purchase of lifetime everyone needs to pragmatic and cheap. Each area have their own climate, cost of materials, cost of labour, building code (safety, efficiency, style) and tradition.
Europe spans 40 degrees of latitude - not listing yours is dishonest.
My new dryer is a heat pump. Uses less than half the energy my previous one did. It does take longer to dry clothes, but it's much gentler on the clothes so it's a perfect trade off for me. I'd love to do a heat pump like this for the house but there is so much oil pipeline around me and there's no way a truck with a pile driver can reach my back yard.
We do it. It’s not yet economically worth it but I’ve seen installs. I can’t find it but I saw one that was designed to let a massive shower run continuously with very little heat loss - the water coming out the end of the drain was as cold as the inlet water from the main.
What efficiency are these? Brainstormed this a bit and feels like shower cabins (pretty popular over NE Europe) should have such system as standalone... As in - it collects waste, collects heat and stores it for next shower. Dunno how much energy a typical refrigerant can store tho. Also great fit for Japanese-style smart baths (press a button and water of desired temperature fills and stays warm), tho they seem rare outside Japan.
There are systems that replace the shower drain with something like a heat exchanger, the water is warmed with the drain water right away, no need to store the heat. For example https://www.oeko-energie.de/shop1/de/eco-shower-duschrinne.h... (in German, but the image is simple to understand.)
I think they can recover up to 60-70% of the heat in the drain water. Not bad for totally passive. The installs I have seen are on the main drain for the whole house and located right next to the hot water heater. For it to really work you need a hot water tank, but I have seen some small tanks combined with tankless.
"My new dryer is a heat pump. Uses less than half the energy my previous one did. It does take longer to dry clothes ..."
I used a very modern heat pump dryer in Switzerland all summer and "... longer to dry clothes ..." is an understatement.
A normal, mixed load of clothing took a full 2.5 hours to fully dry.
It reminds me of CF lightbulbs: a failure to solve the real, big problems (efficient and clean generation of electricity) leads to widely distributed pain for end-users (dryers taking hours or terrible, dim, purple lighting).
Far more interesting than hyper optimized electrical loads would be abundant clean energy sources. I would rather have solar panels and free electricity than have utility power and weird, complicated clothes dryers.
... and yes, my analogy is imperfect because the lighting issue was elegantly solved with LEDs. That's unlikely to be the case with clothes dryers, however ...
I've read it before and it's got some cracking info in there. One of my favourite bits was him using propane as a purge gas to get better quality brazed joints, though interestingly he baulks at the idea of using propane as a refrigerant gas!
No the brazing sounds dangerous. How does it not ignite?? Brazing is done with high heat open flame. Unless it's just for back purging? But that sounds even more dangerous - intentionally building up a propane resivoir behind the braze.
Probably because you need sufficient oxygen for combustion. The propane would only ignite where it comes out and mixes. Once the flame travels into the purged pipe it will probably die out for lack of oxygen.
Ticklish though I'm sure to do it properly and safely.
Propane is not an explosive. Environmental concerns aside, millions of people burn propane each day all over the world relatively safely, explosion isn't really the leading concern.
You may be thinking of acetylene. But that isn't really that dangerous in modern usage either.
Where is the propane going when used as a purge? If it stays in the pipe, you may create an explosive mixture. If it doesn't stay in the pipe, you might create a fireball in your face.
They are great if you are looking to use electricity to heat because they are 3 to 4 times more efficient than resistive heaters. It depends on the price of electricity and other heat sources in your area.
If you live in the north where temperatures go below -15 Celsius, air-to-air units aren't as great because they lose efficiency as it gets colder outside. My heat pump has a COP of 3, meaning it can generate as much heat as a resistive heater using 1/3 the electricity, but it shuts off at -15 Celsius because below that point it is less efficient than resistive heat. If your heat pump has a COP of 4, you might get to -25 Celsius before it is less efficient than a resistive heater.
Better, but more costly, heat pumps use in-ground water, either from a pair of wells, or from a deep pond that won't freeze to the bottom, or from many meters of water pipe buried deep enough beneath your lawn to not freeze in the winter. Because of the depth, they always have access to the earth's heat so they don't lose efficiency in the winter.
The Technology Connections YT channel has a couple of good videos about how them:
Reminds me of a surprising armchair heat macguyvering idea I've had: if for some reason you are stuck with resistive heating, you could use an old fridge as your resistive converter, with the cold end inside (cold end outside would be an actual heat pump, but probably not a good one and very limited in placement, likely losing more to the insulation downgrade from the placement): open the door just enough to get the inside walls below condensation of your current humidity level, collect the condensed water in a way that it doesn't just evaporate again but can be carried to the sink.
Why? Slightly less air replacement required to fend off mold, slightly more heat created, because the condensation is the inverse of evaporative cooling. Haven't done the math but I think it's safe to assume that the benefits would be tiny, but if, for some reason, you were limited to resistive heating, doing it this way would be slight
ly less bad.
Except you usually have a very dry environment when heating due to the lack of moisture in the colder environmental air, and need to add moisture to avoid falling out of healthy humidity levels for human beings.
We are talking about large amounts of moisture that need to be added to the air when heating. There is 0 risk of mold in that situation. Ideal humidity: General recommended range: 40-60%; ideal/goldilocks humidity, 50%; mold conducive conditions: 60%+; air when heating: often ~30%.
Perhaps if the house leaks air like a sieve and you just compensate by more heating watts (or if you use some fancy heat recovery ventilation), but in a properly closed shell, with considerable cold outside, your primary problem is getting rid of all the humidity human life produces without the water condensing on whatever surface is coldest. I suspect that we are talking about very different environments.
If you have a house that tight, you need to compensate by a certain number of minimum forced air changes per hour, on top proper ventilation in your bathrooms and kitchen. In fact, modern building code in the US, and likely throughout most developed countries, requires a tighter envelope than the minimum number of air changes per hour, thus requiring, intrinsically, that all houses have ERVs or HRVs. This is all a solved problem, and you are never going to need to dehumidify during the heating season if you are respecting the principles of building science. It is possible to build "too tight" by neglecting basic ventilation principles, but that is not what I would call "properly closed".
Properly built modern houses would certainly not be the realm of slightly less bad resistive heating improvisations. But here in Germany we have plenty of old stock modernised to the point where is sufficiently air tight for insufficient ventilation to become an issue (and often it does!), but not to the point of active ventilation. Moisture buildup is a major concern, particularly at times of heating scarcity (which is when improvisations become more likely) As I said, different environments.
My humidifier uses about 3 liters of water per day for 40m2 apartment during winter, to keep the humidity at acceptable 40%. Otherwise it's extremely dry inside.
I’ve heard that air source heat pumps can be very effective too, and far simpler to install. I wonder if there’s any discussion about converting ordinary AC units into reversible units, which supposedly is basically all an air source heat pump is.
Exterior heat pumps used in humid or below-freezing environments need some kind of defrost mechanism, just like a refrigerator. Otherwise your coils end up clogged with ice and the system stops working. The compression cycle is indeed symmetric, but the second order design constraints are quite different.
Modern setups are really good about managing frost buildup and can be more efficient than resistive heat down to -20C. Waste heat from the compressor is often used for the defrost.
tangent: for a small air-to-air heat pump, what's the best commercially available coefficient of performance (COP) for a zero-delta-T ?
all the common ratings that i've found online refer to COP at a non-zero delta-t over a ranges of conditions. to illustrate my question, if you needed to pump heat from 70°F indoor air to 70°F outdoor air with a 1-ton unit, what would be the best COP you could achieve in 2022 ?
Absolutely but typically two wells, one to pull water from and one to put the cooled water down. You also need a minimum amount of water flow, depending on the unit and how much heat your home needs.
They're considered better than air-to-air heat pumps which become less efficient as the outside temperature goes down. Ground source units remain efficient in cold weather as the water in the well is below the frost line (only the top few feet of the soil freezes). They cost four or five times more than a typical air-to-air unit though so aren't as common.
Some of them are basically multiple bidirectional wells (when installed vertically in a colder climate) so drilling one more for a wellhead is probably possible.
I've got wells on my property. Rather than drill more wells, I am wondering if there's something that could be put in the well to utilize the stable water temperature down below to heat exchange? Seems like there would be a big market - lots of people on wells are heating with oil or propane or electricity at massive costs.
It would depend on the well and the “heat availability” (not a technical term) and how deep it was.
I suspect it could work but it’d be marginal enough as not to be worth it compared to straight air heat pump or an actual field (similarity could a heat field and a septic field be installed at the same time ,,,)
I understood, perhaps incorrectly, that the ground below the frost line is stable year round and if air source heat pumps work more efficiently down to -10C, we know the water isn’t that cold (otherwise it would be ice), so wondering if the efficiency threshold is the same for ground source heat pumps?
I understand that in a few years every new build in the UK must have a GSHP (no gas boilers) and the goal is for every house to have something like it.
I think this manifesto is a piece of genius - I think I shall be studying :-)
GSHPs are rare in the UK and likely to remain so. In practice building regs will require most new homes to have heat pumps but they'll almost all be air-source units. UK winters rarely get very cold (typical minimum design temperatures are above -5C in most of the country) so ASHPs work well all year.
Even better would be to build out (in new build housing estates at least) district heating. This is common in quite a few other countries and it should work pretty well in the UK too - it's always seemed odd to me that it isn't more common here.
I used to have it; it's a technically nice system when working, but the problem is having no choice of provider, no control when it goes wrong, etc.
Makes sense for flats (or dense area of many leasehold houses, if that happens) where there's a management company holding your throat anyway, but otherwise I can't see how it works unless perhaps it was provided by the council (similar disadvantages, just more trust/better outcomes from complaints).
For horizontal designs yes- the rule of thumb is the brine coil area should be around 3x the heated area.
However, the vertical bores don't need much area, just expensive drilling work.
Also, you know, it's the UK Government's plan, so you know it's going to be something that is deliberately designed to not work, but will funnel billions of pounds of public money into private firms with relatives of Tory cabinet ministers on the board.
If the UK Government appears to be doing something "good for the environment" you can rest assured it's only because they've found a way to use it to siphon money out of the public purse.
I don't think the original claim is quite right. The UK govt is banning new gas boiler installations after 2025, but I believe there's a range of alternatives such as an air or ground source heat pump, or a hydrogen boiler.
From what I've read through, replacing my boiler with a gshp would cost in the tens of thousands, not a million pounds.
Somehow all the leaky old cast iron pipes that just about suffice for carrying gas around the country will be able to be used for hydrogen Real Soon Now, and everyone will be able to just go out and buy a new £6000 boiler to replace the natural gas ones they had fitted recently.
Then all we need to do is start turning the natural gas into hydrogen - releasing just as much carbon dioxide as burning it does - and we've got a clean green hydrogen economy!
The plan is to convert the existing pipe network to use hydrogen. British Gas are planning to trial it starting with a village of around 2000 homes next year. Meanwhile modern boilers are often being sold as "hydrogen-ready" in preparation for the switch.
Ground source boreholes are mostly 10-15 metres deep, so not wildly expensive, especially when part of a new construction. You may be thinking of classic geothermal bores? Drilling down to proper hot-rocks would be a much costlier scheme in most of the UK.
I skimmed the plan and didn't find any requirement to use a ground to water heat pump. Air to water devices are mentioned several times as viable heat pumps for this plan. These do not require boreholes.
I think the UK is effectively banning gas boilers and its upto the developer/consumer to choose an alternative - a combination of CHP (local heating), GSHP, but most likely air source heat pumps.
>Many even now are (blower on/off) and (flame on/off). Only the high end ones have variable blowers and flame heights.
There's a few other safety checks the board will do.. check pressure switche to ensure there is draft before attempting to open the gas valve and light off. There's also thermal limit switches to make sure things don't get to hot if your main blower goes out.
On some boards they're inputs as that's what provides the necessary info for the board to provide flash/error codes. Not unusual to see additional standalone limit switches (like what you observed) for extra protection.
HN loves heat pumps; I'll never have one again - utter shite.
I lived in the mountains of Southern California. As part of an FHA loan in buying my childhood house from my dad, we had to "upgrade" from a swamp/evaporative cooler and wood burning stoves and went with a heat pump. The unit and ducting just couldn't keep up. It sighed out slightly warmer/cooler air and, when it kicked on, it pushed outside-temp air into the house that, in winter, would take the unit over an hour to bring the house back to its starting temp, let alone warm it. It really sucks to be cold and to have to get colder before a chance at warming up. It was similarly lame at cooling, though it would keep the house from sweltering if started before sunrise. Temp range outside: 20-40s in winter, up to 90s with a couple of days in the 100s in summer.
We went back to the wood burning stove and swamp cooler.
Something doesn't sound correct now. In an air heat pump, the compressor and a heat exchanger are outside, only warm liquid flows through a hose into the building where its heat is spread out with a room unit. The system doesn't move air in or out.
It sounds to me like the problems with a "portable" AC or heat-pump. They are freestanding units that look a bit like a room air purifier and are similarly meant for a single, small room. These are something one might buy online or at retail with the idea that there is no installation. It is worse than a window unit because both heat exchangers sit inside the conditioned space, and only a temporary/portable ducting arrangement connects the "outside" loop to the outside. They are also low power because they plug into a regular 15/20A power outlet.
We bought such a portable AC unit as an emergency measure during an extended heatwave and wildfire smoke event in the past. We bought the better kind of unit that has intake and exhaust hoses for the "outside" loop. Astonishingly, there are even worse products on the market that lack an intake hose. So they, by design, draw conditioned air through the output loop and then through the exhaust hose! You can imagine how inefficient that is, to be pumping air out of the conditioned space and create a negative pressure across whatever other leaky paths can refill the room.
Our portable unit with intake and exhaust hoses still does not work very well and leaks a lot of outside air into the conditioned space, obviously reducing indoor air quality when used on those smoky days. We had to hack together a big intake filtration box to keep the smoke out by drawing the intake air through a set of MERV 12+ furnace filters. We also added fiberglass insulated sleeves to the air hoses, which improved thermal and noise comfort.
> I want to take a moment to recognize that the Homemade Heat Pump Manifesto has gone beyond 2 million page views. I would like to thank Daox and any other people who may have worked behind the scene to make it possible.
> My initial goal was to make available the knowledge and possibility that anybody with a few tools and gumption could convert discarded air conditioners, and dehumidifiers into very high efficiency heat ources, or cooling sources. Through the years, we have received reports of success from many people, living in many states, and countries.
> Another goal was to make zero money from this project, to give it away and to encourage others to take it, share it, sell it.
> In the beginning I thought that maybe 200 people would find this interesting. Obviously, I was wrong, gloriously wrong.