Heat pumps of the 1800s are becoming the technology of the future
knowablemagazine.org
knowablemagazine.org
Ducts are dead.
The Daikin Alira X is the gold-plated option and cost $8k AUD for 2x2.5kw and 1x7.1kw units including installation. Payback time is about 3 years. The system is oversized, but enables excellent zoning and of course provides cooling which is a must on 40C/104F days.
Why do they seem to be so much more expensive in the US?
Ducted heatpumps are a thing here in NZ and make sense to me, not that I have used one. The heatpump sits in the roof and air is pushed into three or so rooms through ducts.
If building a new house I think ducts would be the way to go.
Most roofs in Australia still aren’t sealed. The air barrier and insulation barrier is the ceiling. The roof space itself is not insulated, so the ducts are exposed to extreme temperatures, thus destroying the efficiency.
Here is just one article on it: https://newenergythinking.com/2018/10/20/dont-use-ducts/
My argument with split systems, at least how they are installed in NZ, is that they are usually installed in the main living area and if there is a second unit, in a corridor.
So corridors are heated or cooled far hotter or colder than they need to be in order to heat/cool bedrooms.
One has mini splits. You definitely don’t generally put mini splits in every single room (like bathrooms or interior hallways) because each mini split requires tubing, is large, and expensive. No, I think it’s way more likely that you would have them in the bedrooms rather than the hallway
But we have many very toasty hallways leading to cold single glazed bedrooms!
In the last few years the central govt has brought in legislation requiring landlords to heat and insulate homes to a certain standard.
Edit: not to mention the huge difference in surface area. Ducts can expose your conditioned air to a huge, poorly insulated surface. Bad for efficiency.
They also recently undid a long held myth about ducts buried in insulation leading to condensation issues. Most areas now allow ducts to be buried as long as you have R19 above and below, or R30 above. When I just installed a ducted mini for 3 upstairs bedrooms, I surrounded my R8 flex duct with R30 insulation.
Like you said, it’s physics.
We have a two-level, five bedroom new build in Auckland which came with a single-zone ducted system. So outputs are the bedrooms plus upstairs and downstairs lounges. The vents are tidy and unobtrusive - much less space than a wall unit in each location.
We're having major issues balancing the temperature across the different rooms as there is one thermostat.
Think setting the temperature overnight for one room with a couple plus a cat vs another room with one of the kids. Basically the wife and I are always far too hot because otherwise we're freezing all the other rooms. Or setting a reasonable temperature in the lounge makes all the rooms icy in short time.
I'm now thinking about forking out the couple of thousand to get a small heat pump installed directly into our room so we can run it separately from the rest of the house.
So if building from scratch, either look into a multi-zone system or separate heatpumps. If you can get separate systems but hidden in the walls/roof that would be the best.
I have the fan programmed to run 10 or 15 minutes an hour regardless of if the heat pump needs to run. It keeps things pretty even.
https://www.amazon.com/AC-Infinity-Register-Thermostat-Contr...
Appropriately placed In-line duct fans and register fans will pull the heated/cooled air where you want.
The stat is that you lose between 25-40% efficiency for "typical" existing installations. The document goes on to explain that an insulated duct which doesn't leak doesn't have this kind of efficiency loss.
[1] https://www.google.com/url?q=https://www1.eere.energy.gov/bu...
Ducts are still needed to circulate air, especially if you want to remove stale air (e.g., bathrooms, kitchen) and bring in (filtered) fresh air (to bedrooms).
I have a CO2 detector that I believe is a reasonable proxy for stale air. When it goes above 1000 I simply open the windows. By the time I remember to close the windows the reading is almost always below 500.
A great option for keeping CO2 levels down in a house is with an HRV (or ERV) [1] that will heat the fresh air coming in to cycle it throughout the house.
I did not 3D print mine, but ordered it, though as an early adopter, adjustment was required.
> During the warmer seasons, an ERV system pre-cools and dehumidifies; During cooler seasons the system humidifies and pre-heats.[1] An ERV system helps HVAC design meet ventilation and energy standards (e.g., ASHRAE), improves indoor air quality and reduces total HVAC equipment capacity, thereby reducing energy consumption.
> ERV systems enable an HVAC system to maintain a 40-50% indoor relative humidity, essentially in all conditions. ERV's must use power for a blower to overcome the pressure drop in the system, hence incurring a slight energy demand.
In Jan 2023, the ERV wikipedia article has a 'Table of Energy recovery devices by Types of transfer supported': Total and Sensible :
> [ Total & Sensible transfer: Rotary enthalpy wheel, Fixed Plate ]
> [ Sensible transfer only: Heat pipe, Run around coil, Thermosiphon, Twin Towers ]
Latent heat: https://en.wikipedia.org/wiki/Latent_heat :
> In contrast to latent heat, sensible heat is energy transferred as heat, with a resultant temperature change in a body.
Sensible heat: https://en.wikipedia.org/wiki/Sensible_heat
There's a broader Category:Energy_recovery page which includes heat pumps. https://en.wikipedia.org/wiki/Category:Energy_recovery
Are heat pumps more efficient than ERVs? Do heat pumps handle relative humidify in the same way as ERVs?:
That seemed like the easiest thing to do without making much more complicated system. Basically risk 1hour of bad air for 23h of "clean" air.
I was responding to a comment that presupposes the need for fresh air. If you don't need that, feel free to close the windows then.
Following the thread of conversation, it just didn't compute to me:
>>>> Heat pumps are great for climate control >>> Yeah, ducts are dead >> What if you want to recirculate air in your house through your central air filter to eliminate smells? > Just open the window
It's like we've hit a contraction: the premise is that we care about energy but the contractions is then that we don't and we open the window while climate controlling the house. So to me it does seem to prove that in some climates, duct work with a central blower and filter mat not be dead.
Ducts running in an insulated space are sources of huge energy loss.
We've just today had our first snow of the season here in a lower elevation of the Sierra Foothills. It's been chilly for 3 months or so, and our heating is an 'old school' ducted propane furnace. In time, we'll replace it with a heat pump, but not this year. Anyway, we're sensitive to accumulated odors that go with a well insulated, closed-up home in winter.
Every evening, we open three doors in the house to the outside. This is after the furnace has entered its timed 'off for the night' state. We exchange pretty much all of our air for fresh ambient, which is great when we wake up in the morning.
The impact from doing this on our propane bill is undetectable. This is because air, even humid air, has a trivial heat capacity compared to the warm house structure and contents. Those are by far the greatest energy reservoir in our home. Very little energy is lost in a daily air exchange with the ambient.
*edited for typo
I live in Florida, we've used Heat Pumps for as long as I can remember. We also have central air handlers with blowers and ducts to distribute the conditioned air. Mini-splits can _also_ be ducted mini-splits. According to my HVAC geek friend, mini-splits are pretty terrible about humidity control (an important thing in Florida). For proper humidity control you'd ideally have a dedicated set of dehumidification ducts (powered by a central dehumidifier) as well. Mix in an ERV and you have the ability to build a fairly air-tight house with _controlled_ ventilation and very efficient conditioning of the air in the house.
I was going to install an ERV system but the payback was not within the life of the equipment.
Someday I’ll build a Passivhaus with a system as you describe.
This morning it was -5C, so not cold by continental standards, but certainly cold enough.
In the UK recirculating air is very rare. In cases that bathrooms don't have a window (or indeed in new houses where they do) there's an extractor fan, but that just vents the air directly outside.
The only requirement is "2 channel low drift NDIR gas sensor". Cheap CO2 detectors either have zero IR sensors (instead they guesstimate eCO2 using a VOC sensor) or a single IR sensor that requires weekly calibration outdoors or it will just assume that the lowest sensor reading means 400ppm.
No, you can go to ducts by installing them. I believe the comment is advising against doing so.
But I want to know if there is a way uneven spots could cause a problem without some effect tanking the average. What do uneven spots themselves do?
[edit: add link]
[0] https://www.energyvanguard.com/blog/Flat-or-Lumpy-How-Would-...
https://www.buildwithrise.com/stories/ductless-heat-recovery
Another option is to supplement an existing ducted system with a ductless one adding additional zones where you might want conditioning over night. E.g. bedrooms where you want to sleep in cold A/C in the summer where the rest of the house can warm up a bit, or a person in the household who likes their room to be warmer than everyone elses in the winter.
>A recirculating central heating system doesn't do that.
They definitely circulate air, and they definitely filter the air. Whether there is fresh air depends, mostly no.
ERV/HRV has its place it less moderate climates where there is significant efficiency loss from pulling in outdoor air, especially if indoor conditions require a significant amount of fresh air turnover. But a central HVAC system with a recirculation fan most definitely can be beneficial in a lot of cases.
It's really a very good proposition. Has all of the advantages of central heating and the efficiencies the heat pumps
How do you move the heated/cooled air into/around the house without ducts?
A mini-split system puts an ugly, cheap, plastic wall-cyst within your field of view in every room they’re installed.
Nah.
There have been minisplits in the US for years, they are just not very common. Moreover they have been commonplace in Asia for decades now. They are noticeable. I personally think they look like ass. They are huge and you are blind if you don't notice them. There is a reason why ducted or recessed models are available internationally for luxury homes. It has nothing to do with Americans.
Ducts are a superior look and experience IMO, just slightly less efficient. Nothing wrong with preferring them.
So people COMMONLY wind up with unbalanced floors, and people typically try to fix it by adjusting the vent register opening with mixed success.
Part of the problem is that the thermostat is biased to wherever it is located. You can get systems with remote add-on temperature sensors, but that doesn't by itself adjust where heat/cold is being sent through a ducted system.
The great thing about a Mini-Split is that you're, at minimum, heating each floor independently with its own thermostat. You can then put in e.g. interior door vents that simply let air pass between common areas and the rooms when the doors are closed.
This can go even further with for example two Air Handlers per floor (quad units) on the east and west. So that as the sun moves, the correct level of adjustment can be applied to only the side of the floor that needs it.
One of the biggest pros (in addition to the improved efficiency of a heat pump) is I heat and cool less space than i did before because i can target individual rooms. When i'm in my office all day I only need to heat my office. When it's hot and I'm struggling to sleep only cool my bedroom. There's no point in heating my living room^^ at 08:30 in the morning if i don't intend to spend time in there till 17:00.
Sure, when it gets to 17:00 my living area might not be comfortable, but that can easily be overcome by turning it on half an hour or so beforehand (either manually or with a timer).
^^ I don't live somewhere where freezing pipes are a concern. But i'd imagine you could just set them differently, slightly above freezing for the rooms you aren't in and a comfortable living temperature in the room you're in.
And mistakes by installers will cost even more. Our installers didn't flare a line set connection properly and it leaked slowly and that was a very expensive bill (especially since refrigerants have changed so much).
Our Daikin indoor units have also had condensate leaking issues, probably due to poor installation.
Ductless heat pumps do seem like the future but I think there are issues with regards to condensate draining, air filtering, and indoor unit cleaning/maintenance and replacement that could be done much better.
I sourced opinions far and wide and in the end it seemed to be a coin toss between Mitsubishi Electric and Daikin. A lot of it comes done to parts availability, and both seem very strong in Australia.
I once looked at a house with a new GSHP horizontal loop installed in the desert southwest US. I talked to the installer and they said the loop was only 12” deep. There’s no way the ground maintains steady temp at that depth, meaning you’re losing efficiency in the hot months when you need it most. Not to mention thermal pollution which will exacerbate the problem and the risk of hitting the loop with even minor ground work. They were adamant it was a good design.
Unfortunately, many installers jump on the bandwagon without the necessary expertise.
Cleaning basically involves a dedicated cover + drain that diverts water to a bucket, and blasting it with what's effectively a "low power pressure washer" I can use indoors (carefully), and "Lemocide" to properly disinfect... And coil cleaner for the fins. Takes me a good 4+ hours per unit, largely spent preparing the area in case there is any rogue spray. (Though TBH I may be a bit obsessive about getting it right.)
I also had a drain leak as you mentioned -- blasting the drain line with aforementioned "low pressure washer" helped with that. Still a bit gross to deal with. (And learning how to properly disassemble and clean the drip tray is the final thing I've put off leaning for a completely-thorough deep clean... I'm a bit horrified anticipating what I'll find...)
So far, it seems to be working! Better than relying on everyone to manually do it (literally this is the instruction in the Mitsubishi Electric user manual).
Yes, over time - any amount of moisture will produce some mold. But it will be negligible.
But one problem is the dust in the house. It will collect on the unit and hold moisture and give a great substrate for mold to grow. But regular cleaning usually takes care of that.
Most of the videos from HVAC people are... sketchy to the say the least.
I've seen videos where they dismantle the whole indoor unit and leave the coil just hanging from the line set or zip tied to the backplate while they take the fan and drain pan outside to clean.
One easy thing we've found that helps with drain clogs is to use a shop vacuum from outside to suck it out (using a towel/rag to get a good pressure seal). Takes around 5 minutes per drain per cooling season.
This video shows a similar process using water pressure to clean the unit: https://www.youtube.com/watch?v=xcIVAv8YbPQ
Some more tips and modifications:
- I cover the electronics in a garage bag held with tape. No need to unscrew the black cover over the power wires to disassemble (I unnecessarily removed this a few times heh).
- I ended up really liking this cleaning shrowd after trying a few; the hard pieces on the sides are key for making it easy to secure nicely, which many others lack: https://www.amazon.com/gp/aw/d/B083S85X97
- I spend more time (like 30min+) spraying the blower wheel so it spins. I alternate spraying with fresh water with spraying diluted "Lemocide" (@10% dilution) from a spray bottle a bunch of times depending how dirty it is. I use this <https://snowjoe.com/products/sun-joe-wa24c-lte-24v-150-psi-m...> which at 100 PSI is 10x stronger than a hand pump sprayer, but 10x weaker than a real pressure washer. I.e. the sweet spot IMO.
- I use foaming coil clean from a can to clean the fins if they're particularly dirty. (WARNING: I have not used in the same cleaning as the Lemocide since I haven't confirmed if they're compatible, so be careful of any reactions if you use both in the same cleaning.)
- I take the outer casings outside for a quick rinse with the hose and dish soap if they're really dusty.
- I tape cheap plastic mirrors at 45 degree angle above the unit so I can see it from above and carefully vacuum the back coil (there are 3 folded over in a U, and you can only see 2 from the front). Otherwise this just accumulates junk and is hard to see. This also really helps with finding the 3x clips at the top of the case that secure it to the back housing.
I may have a few more notes worth sharing at some point; feel free to ping me if you have any specific questions.
Edit: See also this quick video on unclogging the drain line on a Daikin (though I used the sprayer against the tube instead of my mouth...): https://m.youtube.com/watch?v=GDrHe-rli98
Another great thing about having three seperate units is if one breaks, rare as it is, you're not stuck without heating / cooling.
I despair for the rental market right now. High prices and landlords are generally crap at amenities they don't personally use.
If you went with a common US brand you can get a good system with 4 units and a 36,000 BTU heat pump unit for around $6,500 USD installed.
I don't love the wall units - they're pretty ugly, even the new ones. If you're getting a mini-split, the in-ceiling or wall cassettes that are hidden are really the way to go IMO.
I got hung up on the excess line set idea and did a full DIY install of a non-DIY model mini-split. I bought, borrowed, and rented a lot of tools, spent a lot of time researching and learning. I really wish I went with the DIY model.
Despite that lesson, I may do it again when I finish my attic space, but this time I'll add copper line brazing to the list.
I’m mostly curious how these DIY units compare to Mitsubishi, which seems to be what all the installers recommend.
There are also DIY variants where a fixed line length comes from the factory with either a vacuum or a refrigerant in the line. The lines have metal seals on the fittings that are ruptured when torqued down on the equipment.
Stuff I had already specific to HVAC:
-R-410a manifold, gauges, and hoses.
Stuff I went out and bought:
-Nitrogen tank pressure regulator and hose for HVAC.
-Mandrel pipe bender
-Flaring tool
-Micron vacuum gauge
-A slightly better copper pipe cutter and deburring tool.
Stuff I rented/borrowed:
-Vacuum pump from Autozone. Free. It was plenty big enough for a minisplit.
-Full nitrogen cylinder rental from Airgas.
Things I'm glad I did:
-Used a wall mount instead of a pad for the compressor unit. Unit stays clean.
- Pressure testing with nitrogen. It's worth the money and effort to know up front it doesn't leak.
-Followed a more thorough procedure for vacuuming/drying which involves vacuuming down several times and flushing with nitrogen. I got a much better vacuum after subsequent flushes.
Great. You just eliminated approximately 15% of lazy screenwriter tropes for thrillers and action movies. Now they are forced to rely on replacing live surveillance camera feeds with a loop.
Same, and we have just implemented 2 x 7.1kw units along with about 7kwh solar panels. Our heating costs have plummeted and we can survive on days like today (17th Jan) with minimal impact to our comfort.
We are looking at changing water heating next as this is now the biggest part of our utility usage.
Heat pumps need to be scaled for the maximum heating or cooling load, whichever is greater. The optimal situation is that the heating and cooling loads are similar, but in colder parts of the U.S. the heating load is much larger than the cooling load and the case for the heat pump is not so good as a place where the need for heating and cooling are more balanced.
https://en.wikipedia.org/wiki/Syracuse,_New_York#/media/File...
the average temperature is below freezing for four months.
I guess that's the value of having a big heat sink, the Pacific Ocean, at your doorstep: temperatures are more stable.
When it's really cold out (say 25F or below), the heat pump stops for around 10mins to defrost the exterior coils, which means no heat running at all in that period, and this pause happens more frequently the colder it's outside. The end result, our ~1400 sq place took more than 24hrs to heat up from 55F to 72F when we got back after christmas.
Also you don't save any money on operating it, even with the efficiency yade yada the cost of electricity will run you more than the equivalent in nat gas. So nothing but downside.
My limited understanding of the defrost cycle is that it’s most a problem around 0c? If it’s a colder or warmer it doesn’t get triggered as often?
They're pretty quiet, too. You can certainly hear the air coming out, but it's fairly quiet and certainly wouldn't be noisy enough to bother you over tv, work, or anything else.
Installing good insulation is also really important even if you're not using heat pumps! With bad insulation, you're wasting energy no matter what technology you're using.
Also insulating an old home (pre-WW2) could begin to introduce moisture issues in the walls that weren’t there the last 100+ years since the leakiness of the home would dry the structure. Last thing you want is for condensation and water vapor to build up in the insulation and then begin to rot the wood. Modern build have vapor barriers and airtight seals.
I guess my point is to be careful with old structures without considering things. They were built the way they were because those were the materials we had (old growth wood!) and they were designed to function a certain way.
Im not sure I’d spend the money (or desire the inconvenience) on a job like that on my old home. I’m not sure I’d make the money back in savings during my time here. But during a gutting, makes sense.
In Denmark, this was solved by adding a second, modern window on the inside. The outside kept the same look, and it is even more insulating than a single modern window. Is it a bit clunky to have to open two windows ? Sure. But it is better than not having insulated windows, or ruining the appearance of cities.
This hermetically sealed environment that we create for ourselves is bad for us.
1. https://en.wikipedia.org/wiki/Energy_recovery_ventilation
Side note: As a US resident in an area with a ton of mosquitos, I cannot understand why other countries don't heavily use window screens. Lizards a pretty cool, flies and other flying bugs are just annoying and gross.
After spending some years in Italy I developed a partial immunity to mosquito bites. It lasted for about half a year.
Use to be... native species were mostly a problem during summer and during night time.
But since about 15 years ago you had a massive spread of invasive Asian Tiger mosquitos (Aedes albopictus) genomic studies show it was likely introduced via Italy and Albania simultaneously.
Those things are nasty, go 24/7, and are just a very different beast in terms of disease vector.
There are already established population pockets as far North as Switzerland. Yet another problem that is likely to worsen as temperatures continue to rise.
They employ an amazing tactic by sometimes walking up to their target.
You can hear mosquitoes flying, but their footsteps are obviously inaudible.
Obviously this is location dependent advice. If you live in a lifeless suburban wasteland, then outside is no better than inside. If, on the other hand, there is nature around you, and it doesn’t get too cold in winter, then insulation is a pointless exercise! Get a ceiling fan and learn to tolerate a bit of heat.
I, personally, need nature to stay mentally healthy, and having nature wander inside from time to time helps greatly.
That's a feature not a bug.
> This hermetically sealed environment that we create for ourselves is bad for us.
Not at all. Heat recovery vents exist for a reason!
I would feel terrible either knowing I'm wasting half my heating energy, or freezing in my home.
Also, relatively small amounts of electricity. Radiant, just like your soul would become.
About radiant heat: it is nowhere near the comfort of uniform whole-room heating.
Then you put on a jumper, or use a bit of radiant heat if really soft.
Some might say it's the defining feature and purpose of having shelter is that we don't live at the mercy of the weather.
I can't run a business with indoor temps from 24-31c during business hours. Compounding loss of brain function outside of 18-23c is found by every study I've read.
The less exposure to particulate pollution and extreme temperature, the healthier you are, I can't see any arguments otherwise.
From a business perspective, I think you are probably right. I don’t personally find cold affects my brain function (you can put on warm clothing right?), but heat probably does once we get above 30c. It’s summer right now in Aus, might be affecting some of my posting.
For home though, I’m happy for the inside to be much the same as the outside. Mostly though, I just want the interface between my home and the natural world to be permeable. I think that’s good for mental health, and that the pros outweigh the cons. The thing is that you can’t have that and properly insulate it at the same time. So a choice has to be made, and I personally lean towards less insulation/more lizards.
Having said that, we’re all different, whatever floats your boat. If you prefer plastic bubbles inside caves of steel, who am I to judge?
[1] https://amp.theguardian.com/environment/2023/jan/01/rebound-...
But it's not like heat pumps stop working because of your insulation. They just get more costly to operate. And especially the smaller systems can only deliver so much energy to your house. Basically, if you multiply the maximum output by three, that should be above whatever you are currently using to heat your house during a really cold month. If it's lower, it's not big enough.
When it’s freezing cold outside, it seems crazy that I warm the air of my house and then use electricity to keep the fridge cooler than the air I just heated.
Someone needs to make a standard for moving heat/cool through all appliances in a house…
The fridge is simply moving a little of the warmth in your room out of its box, and adding a little more warmth to the room in the process. You lose no heat from the room, which is what matters, really. It would be worse to dump the heat outside! At least in winter. The heat has to be removed in summer if you have air conditioning.
In any case, an exterior heat exchanger and heat pump that can handle a wide exterior temperature is much more heavy duty. This could all end up being less efficient, in practice. House-scale heat pumps can efficiently move heat even from a freezing cold outside into a warm interior. Just as fridges can efficiently move heat from their cold interiors to a warm room.
Even if we consider incandescent light bulbs, which waste most of the energy they use as "heat", that heat is actually being transferred primarily through radiation, so it can escape through windows more easily than the heat that a furnace transfers to your indoor air.
Still, not much is going to hit a window on average. So maybe 90% efficient.
Surely properly installed gas boilers always did that even without balanced flues too.
There is something very very wrong with your equipment (or you're measuring something else not having anything to do with the heating equipment - more likely). A high efficiency furnace has a sealed combustion chamber, the entire thing runs in a circuit vented to the outside - combustion air comes from the outside and it is vented to the outside. If it is not airtight sealed from the indoors, it is broken. Even a mid-efficiency furnace with a non-sealed system will vent 100% of the flue gas outside.
> Natural gas combustion is at best _mostly_ exhausted.
Bullshit for any modern equipment (ie installed in the last 50 years).
But yes, the GP is full of shit. Maybe they have some other non-induced vented gas burning appliance (ie a hot water heater or gas hob), or their measurement equipment is faulty.
Or you live insulated from shitty alliances and low income life.
A friend's husband was killed by a faulty boiler, carbon monoxide poisoning. In 2015 I lived in a house where boiler ignition didn't work and you had to reach inside with a lighter. That unit was definately not sealed.
UK only required consenser boilers since 2005, the ones before that used to air from inside your house.
Whether most boilers are prehistoric, or it's just years of neglect, I don't know.
"It does cost more to run an appliance than to heat with gas."
That's highly dependent on the appliances involved and the price you pay for each fuel. For me, a heat pump is much cheaper to run. You really need to calculate it for each individual situation.
If I'm running my computer to use it & it keeps me warm, there is no way turning on a natural gas heater is going to reduce my costs.
If you have a thermostat in your home, any appliances you use will reduce your heating usage because the thermostat will automatically decrease how much the furnace runs. So, yeah, it’s not wasteful to vent your computer exhaust outside in the winter, but no one’s doing that. On the other hand, it’s not worth it to run appliances you wouldn’t otherwise run unless you have an electric furnace, in which case it doesn’t matter.
Uh, come again? If I am using my computer anyway - why would I exhaust the waste heat outside if I have to heat the indoors anyway? That is wasteful.
Your fridge has the potential to go even higher than 100%, as it's a heat pump. But for more than a temporary effect you'd have to keep replacing the stuff inside it with stuff warmed up to outside temperate, which would have to be between fridge temperature and room temperature. Perhaps slightly impractical.
I really enjoyed reading The Homemade Heatpump Manifesto on Ecorenovator. https://ecorenovator.org/forum/showthread.php?t=484
Voila: everyone has heat pump heating! (And dead compressors).
The dumb thing is having the compressor itself indoors in summer. Should be outside.
Yes, more efficient than a resistance heater. Possibly more cost efficient than gas.
Wastes a lot of water (if you don’t have a well).
A fridge is just a heat pump.
Today fridges are more or less plug and play. Most kitchens don’t have a hole in the wall going outside where the fridge would go. Some kitchens aren’t even on walls facing the exterior (which I dislike, but they exist)
It should net out to no less than the same energy though, right? That refrigerator needs energy to move the heat out of the fridge and into the home. If that process takes more energy than just letting the house HVAC deal with it, wouldn’t the energy bill be higher?
Keeping a big reservoir warm for the sake of keeping it warm only becomes efficient with regular usage.
From a cost perspective, the slight efficiency increase of tankless never pays back over the cost of the unit, and unfortunately, usually the more frequent repairs. The big benefit is the 'unlimited' hot water.
At large scale (think like walk-in coolers of supermarkets), this is actually being done in the form of district cooling [1].
> Someone needs to make a standard for moving heat/cool through all appliances in a house…
The problem is that the piping itself and the circulation required are sources of energy loss, and it's hard enough to keep these appliances sealed so they don't leak their coolant - most coolants have insane CO2 equivalent potentials. It's not worth the effort.
I often see my HVAC cooling when the set-point temperature is actually _higher_ than the outside temperature. Logically, the house is a heat generator, it makes sense physically. The roof is black, etc.
It would offer a good number of benefits if the system could outright open a duct to the outdoor air, and suck it in whenever the local outside temperature is within the range requested by the user. People who are into optimizing energy use (they exist) can go even further and pre-cool their house during the night in summer.
For this to work, all you need a pusher fan, no refrigeration at all. There might be some pressurization problems, like, you may need a duct both for the intake and outlet. Also might require another filter... but air quality would improve significantly.
This is a really "dumb" idea, but it's perfectly in-line with all the new ideas being thrown out there. The new ideas just tend to throw in an additional heat storage mechanism, like a water tank (in the article). You can get a lot more efficiency gains by saving the night's cold in a tank and using it through the day. But on a more basic level, you can pump straight into the house when the conditions are right.
My thought is I should keep them closed due to extra load on the AC to dehumidify the outside air. Or open windows and turn AC to fan-only mode to prevent stagnant air in rooms without windows.
Unfortunately I have only seen commercial humidification units that boil water into steam with the use of natural gas. Without exception, everything for sale for home use uses electricity (you'll need 230V minimum, single phase will do just fine) to boil the water, which is costly (though this year natural gas prices have risen or even doubled, but even in states with cheap electricity it's probably still cheaper to use natural gas).
That said, it still may be more efficient to open your windows, depending on the humidity.
The idea of doing the same in my home has been taunting me for years now. Ideally you'd have two such louvres, one with a push fan in the upper floor and the other with a pull fan in the lower floor to simultaneously eject unwanted heat, bring in fresh air, and boost whole-house circulation. They'd be set up to interface with the thermostat/hvac and would operate when the outdoor temperature at intake is lower than the temperature at exhaust and both are above the set point on the ac.
The biggest problem is really one of convenience. You'd need a filter on the intake and a rather large and powerful fan to overcome that static pressure - ergo, a noisy one. And you'd probably have to fully dismantle the system in the winter to prevent the cold from getting in (the Midwest is cursed with both hot and humid summers and cold and dry winters). It just end up being the kind of thing where the devil really is in the details and you either do it right and it's a huge undertaking or you do it fast and sloppy and its drawbacks won't be worth it.
But I agree, nothing is more infuriating than seeing the AC on and the outdoor air temperature being lower than that of the home. And opening windows just doesn't make a difference since in most 20th century homes there's just poor airflow and no circulation.
https://www.thespruce.com/whole-house-fan-vs-attic-fan-diffe...
Crack open a window downstairs before switching it on.
When it’s colder outside, liquid will evaporate on the bottom and condense at the top through gravity. Once it’s warmer outside, the whole process just stops.
No valves, no pumps, no analog or digital controls. Ok, maybe a fan.
I actually want a fridge/freezer at the cabin that works like this in fall/winter/spring. I know it’s technically moving heat from inside to outside, but I’ve got more wood than electricity to work with.
I see https://www.qats.com/cms/wp-content/uploads/2015/03/Qpedia_A...
How might this be applied to a residential setting?
Won't cooler temps outside make the AC work more efficiently and get to the desired temp more quickly?
Most of these systems have a damper that the system can use to choose how much fresh air is used or how much return air is recirculated so it’s not difficult to use that to just put fresh air in directly with no cooling or heating. Even systems with heat or energy recovery will often have a bypass damper.
You need the humidity to be in the right range as well as the temperature, but it can save a lot of energy!
For something the size of a home fridge the costs would be immense compared to the energy savings. You're far far better off spending that money on more efficient heat pumps and more/better insulation.
The federal limit for the amount of power a fridge can pull is 527 kWh/year, which at my rates (admittedly on the low end these days) is ~$70/year. There are very commonly available fridges that are < 300 kWh/year, which would be ~< $40/year. So before even taking into account the efficiencies you implicitly make back when you're heating your house anyway, that's your per-attached-appliance limit for input cost on building out, maintaining and running that system.
Though, I admit that the idea of a completely silent fridge & A/C is alluring. Here's to hoping we make some breakthroughs on sold-state heat pumps.
It was never pursued further for reasons I discussed in another comment on this thread.
Not really, efficienty aside the heat it puts out the back is coming from inside the fridge... Which is coming from the room housing the fridge. So over the course of a day it should be neutral.
1) Long refrigerant pipes. This is unacceptable because it increases the amount of refrigerant in the systems (refereed to as the charge of the refrigerant). Refrigerants are powerful greenhouse gases so it is important to design low charge systems.
2) Another process fluid (e.g. water or glycol). This adds expense (more pumps and heat exchangers). You'd increase the cost of all these systems by a lot.
Also, both 1 and 2 involve running a new set of single use pipes around your house.
3) Make a "single appliance" household. A design like this has been tried - single AC/heat pump hooked to fridge, freezer, oven, dishwasher, washer/dryer, and water heater. The problem is that you really have do design the house around this and it is quite limiting from an architectural perspective.
Combined AC/heat pump and water heater is a thing though.
Air-sourced exchanger individual appliances are just so much simpler for the consumer.
Not dissing ground-source heat pumps. Those are fine, since they are typically a plumb-once-and-done. You just generally don't want separate appliances which quick-connect.
It can be implemented as a single line of force water flow with 20-25 Celsius. It is viable as both a heat source and a heat sink at the same time.
This thing can be connected to both your coolers and heaters, and thus transfere heat from one to another. Maybe you could even get you desktop computer into the loop.
Usually it implemented on a lager scale, but i don't see why this would work scaled down.
However unless the house was built, and / or the pool installed in a coincidentally fortunate configuration where the AC compressor and the pool filter pump are within a meter or two of each other, these devices cannot be used effectively due to impractical tolerances and insulation needed to mitigate losses from contact with the highly variable outdoor environment.
that makes no sense. effective insulation is no problem at all. In large parts of europe they even have centralized water heating and run insulated hotwater pipes to houses across kilometers without huge losses, hell, for this kind of setup it would even be possible to just run refridgerant, which typically specs at ~15m for minisplits as maximum(with very minor losses) distance
Installing ducts, etc. might take more energy than is consumed over the product life-cycle.
It would add other limitations, such as only being able to put fridges next to exterior wall.
Or most likely it'll add additional installation cost. Money perhaps better spent insulating your house better.
You'd have fewer compatible vendors to choose from. Less competition.
Flexibility is probably way more important than micro optimizations.
They move the heat from inside the fridge to outside. That heats up your home. This reduces your need to heat your home, temporarily.
Generally, every device in your home that uses electricity is creating roughly the same amount of heat as an electric heater would have using the same amount of electricity. Even fridges and freezers, so long as nothing is being vented outside.
Just to be pedantic, but not exactly. The typical design in a domestic heating unit, or refrigerator is mechanical. A fluid is pumped and cyclically compressed/expanded. While electric motors are usually used, they can be driven by any source of mechanical energy; driven directly by a combustion engine is not too unusual.
There are also heat pump cycles that can be driven directly with heat. Refrigerators based on that are relatively common here in Canada in areas without reliable grid electricity. Usually a propane or natural gas flame.
Thermoelectric coolers are actual electric heat pumps; directly moving heat across a semiconductor junction. Not very efficient and quite expensive practically. They're used in those USB drink coolers and to cool down lab equipment. Finding a high-efficiency thermoelectric material that works at normal temperatures and pressures is nearly as much of a Holy Grail as finding a high temperature superconductor.
Are they two sides of the same problem?
I.e. an internal combustion engine implicitly uses some kind of burning fuel; if on the other hand you want to use electricity as energy source, it needs a different kind of engine entirely. But that, as I understand from the post, is not the case here - heat pump as described here can operate on same principle and look broadly similar in its core parts, whether powered by electricity or something else.
They are called https://en.wikipedia.org/wiki/Absorption_heat_pump
But they are much less efficient that electrical ones, adding even a small amount of electricity to the cycle (even if the primary energy is heat) can dramatically improve efficiency.
Notably, the propane fridges used in RVs (which AFAIK usually use ammonia for the refrigerant) are extremely inefficient. They have the huge upside of requiring very little electrical power to operate, but would never be my choice if I wasn't tightly limited on electrical power.
But that is the introductory paragraph, the author is defining what they mean by "heat pump": a device for heating a house which is powered by electricity. You could power it with something else, but the point is to replace natural gas furnaces.
Our fallback is the pre-existing gas boiler which is much simpler, more reliable and able to be powered by a small generator during our all-too-frequent power outages.
If I am still in this home when the current heat pump fails I will seriously consider a ground-source system instead. The ability to operate during an extended power outage is a significant concern and I expect to always retain the gas boiler as a backup.
The tech is not ready if you need a backup. I've lived in extreme cold climate areas and no gas furnace I've had has ever needed a backup.
I live in the city and don't lose power, but I'm hoping to eventually use a EV as a battery backup when the equipment is available and standards are finalized.
A battery in a compact like the Chevy Bolt could power my heating system for several days.
It's not like modern gas furnaces don't require power to operate. In a recent Buffalo blizzard power went out and many people with gas heating still froze and had their pipes burst.
At some point a bit further on, the backup can be simple direct electric heating.
Eh? Most new houses in Ireland have them these days (it's more or less the only way to meet the efficiency requirements). There's never a backup.
> Same thing for induction stoves.
Eh? Again, these are pretty standard these days, and why would you need a backup?
We are living in a developed world with working infrastructure.
Power outages happens only by accident like when an US helicopter tries weird landings: https://www-abendzeitung--muenchen-de.translate.goog/bayern/...
https://www.rcinet.ca/en/2017/01/05/canada-history-jan-5-199...
https://www.cbc.ca/news/canada/toronto/hydro-one-downtown-po...
You're welcome, we bombed all your infrastructure into oblivion about 80 years ago, now it's all new! And also, your country is quite a lot denser than North America, so you can bury every single power cable (though you don't, obviously) and if you think -10C is cold, just wait until you see what much of North America experiences during the winter.
This is common for my area.
During installation we've even made a mistake and it heated the building up to something like +27°C inside during early winter all without breaking a sweat (or my wallet.)
The tech is ready. Many attempts to apply it is what’s getting botched.
* EDIT: having checked, most of europe falls within temperate – the country is up north.
Not only they are used in Scandinavia for years. Also in Germany they are used for years. The company Waterkotte operates since the 1980s in Germany and is a pioneer in this showing it is working.
But there are always people ignoring the facts.
My parents live in rural Scotland and use a ground source heat pump for heat and an induction stove for cooking. Power outages happen more often - but still pretty rarely. If they do, they burn wood for heat and eat cold food for a few hours.
This is not an academic question, especially in North America. The weather here can be very harsh.
We lost power earlier this year as the temparature dropped to 0F (-18C). Our contingency (oil heat, oil generator) kicked in and we were fine, but many people were not.
After power was restored, people with air source heat pumps were still stuck, as the heat pumps don't function well at all at those temps, and heating up a house after it has cooled to a low temp is not what a air source heat pump is good at. These are not problems at all for an oil furnace.
I haven’t had a power outage lasting over an hour for as long as I can remember (years), but that doesn’t mean I’m not considering that scenario. There could be wars or sabotage or whatever. One should always be able to manage for a week or so without power and that will require some form of backup such as a combustion heater of some sort. But having a backup solution that keeps you alive for a week isn’t so expensive. You don’t need two completely separate and redundant heating methods simply because one of them relies on the power grid.
I live in a heavily populated area with high standard of living, and yet we have had power outages lasting up to a week in the years we've lived here. Almost all in the winter, but also some due to hurricanes. We have have solar, which is great in the summer heat, but not as wonderful in the winter. We have air source heat pump, but also oil furnace backup.
We normally run the heat pump when its above 35F, as the efficiency of the heat pumps drops like a rock below 40F and its just not worth running below 35F. The heat pump is not an ancient POS. It works great 99% of the time, but 1% of 365 is 3.65 days per year. Banking on "most of the time" to be alright all of the time is foolish.
We have diesel generator in case of power outage, which allows us to run the oil furnace using the same fuel as the furnace. This strategy has allowed us to ride through many 1% case scenarios without drama.
Looking at [1], I can see only two power cuts lasting more than 24 hours (Barcelona, 2007 and Cyprus, 2011).
Instead, "major power cut" refers to things like "The power cut occurred at 4:20 pm and power was slowly restored between 5:20 and 6:30 pm." (Glasgow, 2009.)
I can't remember being without power for more than 6 hours, and it's probably more like 3 or 4. I've been responsible for some colocated servers for about 8 years, and there's been one occasion where grid power was lost. That was about 20 minutes. A Raspberry Pi I have in a village in England has lost power once in the last three years.
[1] https://en.wikipedia.org/wiki/List_of_major_power_outages
Maybe you are in the USA? The infrastructure situation seems to be different there. We don't have any above-ground power lines in this country (except for high-voltage long-distance transmission trunks) and in the past ten years the power has gone out exactly twice, according to my uptime logs - once for 40 minutes and once for about three hours.
I'd also suggest that the necessity of a backup plan can be reduced as well. Having an unreliable power grid is probably not an immutable law of nature so much as a policy choice and modern heat pump technology performs well at considerably lower temperatures than you describe.
I'll also have solar + battery. Should be able to run the furnace & fan but not the heat pump (too many kW/h) during a power outage and thus heating with gas. It'll run off the heat pump for 90-95% of the year, only using gas on the coldest days, or during an outage. To go full heat pump for 100% of the year you need to seriously upsize the heat pump(s) and you wouldn't have performance during an outage.
You could still circulate air with the blower running in fan mode and you may not need humidifiers as that’s the biggest negative to forced air heat imo.
Curious which humidifier systems you’re looking at?
I put in heated electric floors in the bathrooms (about $1k each).
Byrant has a humidifier (https://www.bryant.com/en/us/products/humidifiers/) that integrates with the system. It also has integral HRV. As well as an air purifier: https://www.bryant.com/en/us/products/air-purifiers/dgapa/
It's not a bad compromise for our climate. Currently living in a home I designed that has mini splits everywhere and I really dont like them. Not enough air circulation and it's really hard to balance given a well insulated house on mildly cool days which is very common here.
I intend to always keep the fan going to circulate the air in order to clean (we have allergies) and humidify.
Smart man.
> Currently living in a home I designed that has mini splits everywhere and I really dont like them.
I have a similar opinion. They're fine in a 1-off room that is isolated but I don't like them much otherwise. They don't look good at all.
You’re right though, they take awhile to heat up and if you’re in a place where you may need heat at night and AC in the day, they won’t be ideal.
Not to mention radiators are sort of lousy ways to heat a room anyways. They take up space and leave one side too hot and the other too cold.
I guess it depends if your natgas bill has a big fixed cost (and I guess you’ve already covered the sunk cost of connection…)
Myself, I would like a ground source system that lets me store in heat from an oil fired AGA, a wood burning furnace and water heater panels on the roof.
Of course, the question is at what scale we can build such systems and if that would raise water temperatures significantly.
I am not a biologist.
https://en.wikipedia.org/wiki/Outdoor_wood-fired_boiler
If you have enough sufficiently dry wood, downdraft gasification models burn extremely cleanly (they're effectively rocket stoves), but those models require a fair bit of maintenance, especially if your wood is slightly wet or green, because soot can quickly build up on the water envelope.
That is a standard package provided by many companies from Austria and Germany.
In Germany if you want to build a house, almost every construction company will default to some variant of heat pumps. Actual plumbing companies are more likely to recommend an air-sourced heat pump, prefab construction companies seem to have taken a liking to air-air heat pumps (which like air conditioners pump hot air into rooms rather than running hot water pipes through the building for heating) but either way it'll be a heat pump of some kind or another.
Also not only is there a legal minimum requirement for insulation but all grants and subsidies (when available) specify a minimum standard for insulation that must be met. Note that in new constructions they're also combined with a ventilation system to prevent mould and improve air quality. In older buildings retrofitted with modern insulation, tenants are usually instructed on how to vent by opening the windows.
On the other hand, air conditioning is almost unheard of compared to the US outside retail. Even office buildings usually only have desk fans.
At its very simplest it is just a box where incoming air is being heated by outgoing air without both getting mixed. It is a bunch of pipes, radiators and two fans in a box.
Whether you heat or cool your house, an open window is energy loss. The heat exchanger lets you keep your house nicely ventilated while reducing those losses due to ventilation by something like 90%.
The cold fluid will meet (thermally, in adjacent pipe) more and more hot other fluid and finally as it reaches the end it will meet the hot fluid at exactly the temperature it comes in. If the fluids are flowing slow enough and the thermal bond is good enough, the cold fluid can get heated up as close to the hot fluid temperature as you want.
And the hot fluid will meet colder and colder other fluid until it reaches the coldest at the other side.
The efficiency of heat exchanger could be as close to 100% as you want, in ideal world.
In real world higher efficiency requires larger device and there is a point of diminishing returns. You also get other losses like mechanical losses due to need to pump fluids through pipes (with large surface area), due to need to have turbulent flow (to ensure mixing within pipes) and due to heat loss to the environment.
https://en.wikipedia.org/wiki/Energy_recovery_ventilation
I think another part of this is that there is generally a significant moisture content difference between hot and cool air, leading to some additional gains versus thinking in terms of air temperature alone.
And conversely, if you live in very hot and humid climate, you need to remove water from incoming air (actually, there is no other way to cool the air). This unfortunately further warms the incoming air and will necessarily lower efficiency of the exchange. Especially because you don't want to remove only minimum humidity -- you probably want to remove enough of it to get to at least 70% for comfort.
So these are extreme climates. In a more moderate climate you can get away with no need to add or remove humidity and you can get as close to 100% efficiency as you want.
FYI the "industry term" for these is an ERV or Energy Recovery Ventilator. (I think I've seen them referred to as Enthalpy Recovery Ventilator -- but I assume that fell out of favor since it's too pedantic for most people heh.)
If you get one, one tip is to ensure the air inlet is covered with a fine mesh screen. This cut the number in bugs in the filter 95%+. Also you can upgrade the filter from what's included to MERV13 or whatnot for better incoming air filtration.
I sort of knew this for a long time and that's why I, for example, always sleep by an open window. But knowing it is one and actually seeing a completely different thing.
So this caused me to start thinking about installing one or more of these boxes in my apartment.
But ducted are not as efficient compared to ductless due to the long runs of ducts and cold attics (even if ducts insulated). Plus my province won't give any rebates for ducted only ductless.
Even better would be ground-source heat pump. But still I'd prefer ducts I think you'd have to with a ground source system.
That’s the kind of speed we need if this is going to be any help before everything’s on fire anyway.
From what I can tell (in / for the UK at least) heat pumps currently aren’t that great - my dad’s boiler just died and every plumber he spoke to said heat pumps kinda suck and to just get a nice new gas boiler…
Heat pumps are extremely excellent, and have been for years. We've even reached the point where heat pumps are able to work effectively in places like North Dakota. For reference, the UK doesn't even have the concept of weather like that.
Similar issue in the states. HVAC specialist trash talking mini splits because a mini split's advantage of cheaper maintenance and install is meaningless to the HVAC specialist. Instead they only see the trade offs. Then they quote a bill as if installing a mini split requires a diploma and point out just how uneconomical the farce is.
What did they say precisely?
Heat pumps are used to heat a storage container called buffer, a water container of 200l or more of water. This is used to run the heat pump when energy is cheap to warm up the buffer. That is for example in daytime when energy is available from the photovoltaic. If you don't have photovoltaic you can also have a good energy price when running this at night.
Also the storage of the heat in summer is nothing new. These systems are also commercially available for years. It is only that they are so expansive that many companies have backed out of those.
The idea here is that in summer time you heat up a big tank in the ground like with a thermal system on your roof. Then in winter time you use that "saved" energy to run the heat pump. At the end of the winter the water in the tank will likely be freezing. That state change of the water will give an additional energy boost, because it is the same amount of energy you need to boil water. All this is well known and working and commercially available for years.
Some irony on a story with the title "Heat pumps of the 1800s..."
And how does it fit into existing setup? I can imagine it can be connected before water boiler to supply the lukewarm water.
https://www.smallplanetsupply.com/sanc02
https://r744.com/co2-heat-pump-water-heater-market-for-homes...
I've seen that story a few times now. The free time let a lot of innovation happen. Fuck jobs
So they are ready.
-1F is -18C
-1C is 30F
Even for less effective heat pumps, gas backup isn't really a requirement since you can often use electric "heat strip" backup like my home does. Heat strips are not particularly energy efficient, but many places that can get cold during the winter aren't continuously cold, so a less efficient electric backup is just fine.
In Vermont, we are in our first year with heat pumps. Have a wood stove as backup and supplement when we want to go pantsless mode. The original oil burner is currently turned off, out of commission waiting on some parts. We could go without the wood stove, and have done so for stretches.
We installed Mistubishi Hyperheats, 3 external units, 5 heads. Zero interest financing by installer, for about 21k all in including electrical work. Earlier this year we also did air source hot water heater, for about 4k all in.
We were spoiled by the whole house air conditioning over the summer, and the heating has been performing just fine. It about doubled our electric consumption, but that bill is still less than my oil bill was, before the price of oil nearly doubled.
We're motivated primarily by a desire to minimize fossil fuel consumption, and then to mitigate volatility in fossil fuel markets. With this install we completed electrifying all utilities in the house , and have a rooftop solar array that previously offset the entirety of our consumption, but will not at current levels.
The heat pumps will just about pay for the cost difference between them and a new oil burner before their parts warranty is up. Add in the cooling, and the increased control and comfort we have, and it's a pretty sound investment, IMO.
As an anecdote, the conversation at the local bar in Rutland, VT the other night was all about people planning to get heat pumps, or promoting them after having them installed. Not wealthy tech enthusiasts, but bartenders, small business owners, and working class families. With the IRA inventives, and the price of heating oil -- it's becoming a normal thing, not an exception.
Its not a one size fits all solution, that's all.
If you have to have a backup it is _not_ a replacement and it will not get us off of carbon. Most people cannot afford a heat pump system much less a heat pump _and_ a furnace. Heat pumps seem great for moderate climates but it is not gonna happen up north where things actually get cold and stay cold for long periods of time.
Anyone who actually has experienced this type of cold would run in the opposite direction of a heating technology that produces less warmth the colder it gets outside. Literally the opposite of what is needed for existence.
The author is not "pulling crap" because they point out the real experience of Norwegian home owners while also describing the diversity of heat pump installations and outcomes.
They're actually being very honest.
Also, Norway doesn't get as cold as you might think. They get some heat from the gulf stream in the Atlantic ocean like the UK does. Russia and Canada get a lot colder in their northern parts, like -40C quite often and sometimes even as low as -50C. Heat pumps aren't very viable below -25C, but work is ongoing to make the more efficient at lower temps.
This works great since all houses, including those 100 years old, are well insulated.