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04-06-2020, 07:46 AM #1
Home Heat Pump for a mild climate
Does anyone have a heat pump in their home and live in a mild climate? Does it work well for you, and what should I know? I'm considering adding one to my Seattle home at some point in the future. The house is 106 years old, has some insulation, weather stripping, etc. but is still super old and not very well insulated with many single pane windows, etc. I added a ton of insulation to the attic before we moved in. We have a gas furnace which is maybe halfway or more through its life. It heats the house just fine and I have no problems with is. We also use gas for hot water and cooking range. We used 849 therms of gas last year, of which I estimate 753 was for heating. We use a smart thermostat, turn the heat down when we are away, and keep it set to 68 in the winter.
These are my main reasons for considering a heat pump:
- Burning up natural gas when I could heat with low-emission electricity seems stupid. My house is old, and I dislike having a nearly 1:1 ratio between burning gas and not feeling cold in the house. I've added the amount of home insulation that makes sense and is feasible.
- Having the ability to use AC in the house is not something I frequently want/need, but on the occasion that it is hot and the air quality is bad (i.e. in a bad summer fire season) having the option would be great. We currently have a "portable" AC unit that gets used a few times a summer. It works but is load AF and annoying to deal with.
Do people ever install a heat pump and keep their gas furnace as a backup? I think I have room in the basement for both, and like the idea of having redundant heating systems.
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04-06-2020, 08:10 AM #2
Home Heat Pump for a mild climate
You’ll need to add ductwork for a/c, tho likely not that much
Keeping a redundant forced air system is gonna add an entire second system of ducts, which you likely do not have space for...( I’m guessing the add’l a/c ductwork may be a challenge)
If you have a great centralized duct system, heat pump could be a great option
Multiple mini splits might be cheaper and more efficient (if the ugly head units don’t bug you, potentially duct free too). That would be the easier redundancy, if that really was a consideration
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04-06-2020, 08:35 AM #3
Heat pumps do fine to about 30. Our last house in the Midwest, we had a dual system - heat pump for cooling and heat down to 30, then a gas furnace that took over below 30.
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04-06-2020, 08:42 AM #4
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04-06-2020, 08:44 AM #5
I’m in Seattle. Electric baseboard heat. No AC. No ducts. I’ve priced out a few companies to do mini splits - 1 ceiling unit and 2 wall units.
Mitsubishi and a few others make a horizontal ducted mini split. It’s a fan cool unit you can hide in your basement or attic (wherever your existing ducts are) and run hydronic outside to a minisplit heatpump. Tie the unit into the existing ducts with a manual damper on the furnace... just an option. No idea what is cheaper and more efficient.
All the AC guys were trying to upsell me on buying that unit and running ductwork in my attic...
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04-06-2020, 08:44 AM #6
Yes (assuming a somewhat recent furnace)
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04-06-2020, 09:22 AM #7
What additional ductwork would I likely need for AC? There are ducts for heat from the furnace to just about every room. Does AC require different ducts? I certainly don't have room for more.
Were they mini splits or did they use the same ductwork?
I have found windows and related installation cost to be expensive AF - I also know they are generally not the biggest source of heat loss. Also, in terms of emissions, switching from gas to near-zero emission electricity seems a lot better than just burning less gas.
Sounds interesting. I think my issue would be that I need heat to flow mostly into my 1st floor in the winter (because the heat rises) and then in the summer I need it to flow mostly into the 2nd floor (because sun heats it up a lot more). Perhaps the damper allows that to happen. I have manual dampers on a few of the ducts coming out of the furnace and I've been using that to tune how much heat flows to each room. I was inspired to do this when I brought my work computer home and realized what an enormous amount of heat it produces.
I have relatively little space outside the house, so placing the unit(s) could be tricky. The lot is small and a driveway directly abuts the entire W side of the house - the side you would definitely want AC to serve directly.
Thanks for all of the advice so far!
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04-06-2020, 09:31 AM #8
A/C for heat pump requires a return loop in addition to a supply duct loop. So, likely you need returns to make your duct layout work. These can be minimal (far less than a new layout might be set up for).
Mini splits can be ducted or ductless. The ductless ones are a kind of modern version of that wall unit every motel room had. The thru-wall units are nicer than the motel version but still a bit of a dog. If you have high ceilings and can sort of get them out of the way, then they aren't too bad. Basically a head unit will service 800-1200sf of somewhat contiguous space (no ducting). VERY VERY efficient and cheaper than a heat pump usually. There will be a compressor outside (12" x 30" x 24" or so), a lineset that runs to the head unit, and the head unit on the wall or in the ceiling -- no ducts. They do both A/C & heat. You can run multiple head units off a larger single outdoor compressor to get zones thru the house.
Yes, expensive, re: windows. But they are one of the first items to look at regarding energy loss. Insulation is cheap at the price. More = better in almost all cases. Disagree that the zero emission bit is more important. (not unimportant, just less)
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04-06-2020, 10:17 AM #9
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04-06-2020, 10:32 AM #10
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04-06-2020, 11:09 AM #11
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04-06-2020, 11:54 AM #12Registered User
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We are in the Okanagan and have a heat pump. I think the OP mentioned he does not have a lot of room outside his house which tells me the homes might be close together. Before making any decisions he needs to visit a heat pump in action and see how loud it is as his neighbours may not appreciate the noise. While not loud, our airtherm (not geotherm) unit is quite new but also not silent by any means. Our neighbourhood is all one acre + lots so it's not an issue.
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04-06-2020, 01:44 PM #13
My existing furnace system has a single cold air return at the bottom of the central stairwell. Does the return loops that AC requires do something more/different?
The mini split makes a lot of sense, but due to fairly low ceiling on the second floor and limited space on the S and W side of the house, it may not be a good fit.
My attic insulation is maxed out, and that helped. I also have added interior storms in key areas. I'm not ready to tear my house apart for moderate efficiency gains due to cost, time, hassle, mess, etc.
Why do you think that low emissions energy source is less important than insulation?
Thanks for all this great info!
If it can truly work well down to 10F then clearly that should be good enough for Seattle.
The houses are close together - although it's actually a fairly noise area already on the side of the house where it would go, so noise is not an absolute show-stopper. I had considered wanting to check out the noise, and definitely will be sure to now.
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04-06-2020, 02:16 PM #14
In older forced air houses, sometimes they didn't do returns, esp at upper floors. If you have a ducted return, then it may be fine. If the air doesn't have a proactive way to circulate, it can cause stale areas in the house. It sounds like you have that issue with no returns at the second floor...
Think of trying to put water into a water balloon that is already full. It needs a leak or a drain to encourage water to move thru the whole space of the balloon
The first line of defense is a good thermal envelope because it's a one-time cost, whereas the energy source is a continuing cost however low it may be.
There may be a ROI calculus there where there's a diminishing return in a moderate climate, but, as a rule of thumb, insulation is cheap at whatever cost it is, AND THEN, the cost of energy follows
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04-06-2020, 02:49 PM #15
Well to you point it's probably worth getting an energy audit to see if there is any low handing fruit left with regards to insulation. (Insulation is amazing of course - I'm just trying to be realistic about the tradeoffs when it comes to an old home.)
Thanks again for all the advice - great to get a brain dump before starting with quotes and contractors. Clearly that is going to have to wait a while anyways....
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04-06-2020, 05:55 PM #16
The Mitsubishi hyper heat series are still putting out heat at outside temperatures of 15 to 20 below zero F. I have used them on many projects in New England.
You’d want an accurate heat loss calculation to size a new heat pump air handler correctly (this would replace the gas furnace). I think they max out at around 4 tons / 48k btus, but that may have changed.
Upgrading the envelope is good advice, insulation, air sealing, windows etc.
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04-07-2020, 07:58 AM #17
This. We heat in Southern VT with only CCHPs. 2 exterior units and 4 air handlers. About 2,200 sq ft. We lived in Tennessee in the mid 80s and our heat pump there was not enough. The new technology is amazing. We got warm air coming out of the air handlers at -10F the last 2 winters. We have some electric baseboard as a backup but haven't needed it since we installed the CCHPs 4 years ago. Exterior units are very quiet and ours (Daikin) actually have a "whisper mode" which makes the exterior units even quieter. Getting ready to install a unit at a house in SW NH because we have been so happy with the performance of the ones in VT. The NH house has solar so we aren't contributing to climate change....
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04-07-2020, 10:06 AM #18“The best argument in favour of a 90% tax rate on the rich is a five-minute chat with the average rich person.”
- Winston Churchill, paraphrased.
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04-07-2020, 10:23 AM #19
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07-19-2022, 11:50 AM #20
Anyone w/ experience with MrCool heat pumps? My old AC compressor locked up but it looks like I can install a hp condenser, change a valve in my coils, and get ~ 20 seer efficiency on the cooling side, 10 hspf on the heat side. And still have a gas furnace (relatively new) as backup for quick heat ups after being gone or as backup. I see 2-ton units for around 2k and my compressor fix was quoted at 2500!
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07-20-2022, 01:25 PM #21
FWIW, something else to consider when facing the OP's problem with an old house is sealing the attic to stop air leaks.
Comfort isn't just about temperature, it's about draftiness and equipment noise too. Insulation is air permeable so sealing air leaks, especially in the attic, makes the biggest difference in comfort and energy.
Otherwise cold, hot, or even polluted air is pulled into the house due to pressure differentials caused by a stack effect where an unsealed attic acts like a chimney.
Air sealing can make a house feel more comfortable even if the thermostat is set a couple of degrees lower in the winter or higher in the summer compared with before sealing the attic.
https://ene.org/air-sealing/
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07-20-2022, 01:40 PM #22
Anybody here have heat pump clothes dryer? I replaced my 25 year old Whirlpool washer yesterday with a new energy star top load fancy dancy whirlpool. My old natural gas dryer looks like an antique next to it.
Googled heat pump clothes dryer and hot damn. They look viable.
https://www.washingtonpost.com/lifes...599_story.htmlLast edited by uglymoney; 07-23-2022 at 11:27 AM.
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07-24-2022, 12:42 PM #23
Vaguely heard of them, and I believe their main product line and main claim to fame is for mini split HPs, not what I believe you are describing as an outdoor unit feeding into an indoor unit (your gas furnace).
20 SEER rating is very good, and I'd double check you can get this by changing out only your outdoor unit and keeping your existing indoor unit.
Typically HP systems last 10 to 20 years. Assure yourself that over the 10 to 20 life of the equipment you can get parts/service and repairs, as MrCool is not of the main brand lines.“The best argument in favour of a 90% tax rate on the rich is a five-minute chat with the average rich person.”
- Winston Churchill, paraphrased.
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07-24-2022, 09:58 PM #24
When people if you have recently had an 18k btu mini split or similar installed recently, what did that cost you? Thinking a single condenser, single indoor unit, uncomplicated install, including electrical.
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07-25-2022, 06:34 AM #25
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