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  1. #1
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    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.

  2. #2
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    Home Heat Pump for a mild climate

    Youíll 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...( Iím guessing the addíl 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 donít bug you, potentially duct free too). That would be the easier redundancy, if that really was a consideration

  3. #3
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    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.

  4. #4
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    Would replacing the remaining single pane windows be a better ROI vs adding a heat pump?
    Quote Originally Posted by powder11 View Post
    if you have to resort to taking advice from the nitwits on this forum, then you're doomed.

  5. #5
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    Iím in Seattle. Electric baseboard heat. No AC. No ducts. Iíve 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. Itís 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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  6. #6
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    Yes (assuming a somewhat recent furnace)

  7. #7
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    Quote Originally Posted by ::: ::: View Post
    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
    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.


    Quote Originally Posted by Skistack View Post
    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.
    Were they mini splits or did they use the same ductwork?


    Quote Originally Posted by El Chupacabra View Post
    Would replacing the remaining single pane windows be a better ROI vs adding a heat pump?
    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.

    Quote Originally Posted by nickwm21 View Post
    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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    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!

  8. #8
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    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.



    Quote Originally Posted by Dromond View Post
    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.
    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)

  9. #9
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    Quote Originally Posted by Skistack View Post
    Heat pumps do fine to about 30.
    Newer cold climate heat pump (CCHP) technology works very well down to 10F and okay down to -10F. CCHP is the standard in our area for new construction. Maybe not relevant to OP's query.

  10. #10
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    Quote Originally Posted by Dromond View Post
    Were they mini splits or did they use the same ductwork?
    Same ductwork. Everybody has both heat and a/c there. You can probably count on your hands the number of days/yr. you're not using one or the other.

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  12. #12
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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.

  13. #13
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    Quote Originally Posted by ::: ::: View Post
    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)
    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!


    Quote Originally Posted by GeezerSteve View Post
    Newer cold climate heat pump (CCHP) technology works very well down to 10F and okay down to -10F. CCHP is the standard in our area for new construction. Maybe not relevant to OP's query.
    If it can truly work well down to 10F then clearly that should be good enough for Seattle.


    Quote Originally Posted by apex dave View Post
    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.
    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.

  14. #14
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    Quote Originally Posted by Dromond View Post
    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?
    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

    Quote Originally Posted by Dromond View Post
    Why do you think that low emissions energy source is less important than insulation?
    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

  15. #15
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    Quote Originally Posted by ::: ::: View Post
    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
    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....

  16. #16
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    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.

    Youíd 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.

  17. #17
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    Quote Originally Posted by GeezerSteve View Post
    Newer cold climate heat pump (CCHP) technology works very well down to 10F and okay down to -10F. CCHP is the standard in our area for new construction. Maybe not relevant to OP's query.
    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....

  18. #18
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    Quote Originally Posted by ctsmith View Post
    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.
    ^ what he said about the heat loss calculation. Not everyone does these calcs the right way, so ask around.

    hvac-talk.com = TGR for the hvac trades. Look at the AOP (ask our professionals) section.
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  19. #19
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    Quote Originally Posted by ctsmith View Post
    The Mitsubishi hyper heat series are still putting out heat at outside temperatures of 15 to 20 below zero F.
    They have become the standard for new single family construction in our area. All (7) houses on my street have them. 3 years ago all of them stopped heating one night when the temp dipped to -18F. They all started working when it warmed up to -10F or so.

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