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    Posted: 28 Oct 2022 at 4:00pm
Originally posted by StephenH

My sister and her husband installed a ground loop heat pump. It took some doing in the rocky soil of western NY. One part of their yard was solid rock so they had to route around that. It is more efficient, but I agree. There is nothing to see. A fireplace or wood stove with window is much more pleasant to look at.

We have a fireplace, but prefer to use the gas pack furnace/AC for heating and cooling. We used to live in a house with a heat pump. Our electric bills in winter were sky-high and that was keeping the heat turned down. We had a couple of oil-filled electric heaters to use at night in the bedroom since that was a more even heat than the heat pump could provide. I don't want to live in a house with a heat pump for heat again. Natural gas heat is much more affordable.

That is no longer true.  The old style heat pumps quit being effective around the low to mid thirties. Below that all they do is blow cool air so the resistive heat strips have to operate  and that is where your costs skyrocket. 

The new cold temp temp heat pumps are much improved, and work well down to around 15 degrees or even lower.The Japanese have led the way in this tech, with their inverter based  minisplits. Look at the Mitsubishi hyper heat for example.  That is the way to go nowadays. It will be significantly cheaper and  cleaner than gas heat going forward  and as more and more cities ban new gas installations it will become a bad investment to have one of those systems. 

It also makes ground loop heat pumps less attractive financially  because the benefit of a ground loop heat pump is that the ground heat source is warmer than the air so the heat pump is both more effective and efficient. But if a similar benefit can be achieved without resisting to digging up your yard by using a better air to air heat pump why do it? 

If you look at the btu content of wood on a per pound basis rather than a per cord basis it really doesn't matter what kind of wood you burn as long as it's seasoned properly. Oven dry hardwood holds about 8600 btu/lb. Resinous softwoods are slightly higher at around 9000 btu/lb. Basically, a pound of cellulose is cellulose. Ppl like to burn hardwood because it's denser so if they're buying a cord they get more btus. But if you're harvesting your own wood it doesnt  really matter.  So I just burn whatever I have available. If it's wood and it's dry I burn it. If it's green I don't even try. You're just wasting most of the chemical energy in the wood vaporizing water. 
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Posts: 6288 		Post Options Post Options   Quote StephenH Quote  Post ReplyReply Direct Link To This Post Posted: 28 Oct 2022 at 4:30pm
https://evolvedthermal.com/ground-source-vs-air-source-heat-pump/

Ground loop will still be more efficient than air source.
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Posts: 5290 		Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Posted: 29 Oct 2022 at 5:14am
That company is trying to sell geothermal so they're not comparing themselves with up to date air source heat pump technology.
 
That being said, of course a geothermal heat pump will always be more efficient when it's cold, because the ground heat source will be warmer than the air. 

But would that difference in efficiency ever  pay back the much higher installation cost? Its cheaper most places  just to add some solar modules to make up the difference in electricity usage. 

In a very cold climate where even a new high performance air source heat pump won't work then sure a homeowner should consider ground source. But in those climates ground source gets very expensive because the frost depth and ground temps require a very large deep geothermal loop or it can freeze up since it is continuously extracting heat from the ground all winter.  I'd like to be wrong but I don't really see a cost effective alternative to combustion in those climates. Keep those wood stoves going! 
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Posts: 1214 		Post Options Post Options   Quote David and Danette Quote  Post ReplyReply Direct Link To This Post Posted: 30 Oct 2022 at 7:12am
   I think when we replace our Carrier package heat pump we will replace it with the better design Carrier package heat pump the Performance 15 50VR  it has a more efficient heat pump I think like what offgrid had mentioned with a two stage compressor. By the past posts wood is a popular option for heat and watching the national news it mentioned someone installing a wood burning stove to replace an oil burning furnace to save money from the high price of oil.
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Posts: 6288 		Post Options Post Options   Quote StephenH Quote  Post ReplyReply Direct Link To This Post Posted: 30 Oct 2022 at 8:51am
Part of the problem is the frost level. I saw two types. One used a run that was bigger, buried so that the ground loop was wide and shallow. The other was deep and the loops were installed vertically. Those would likely work in the really cold climates. The need to dig deep for a horizontal loop would likely not be too much more than drilling for a vertical loop.

What makes the air source so much less attractive is that when the heat just isn't there to extract, pure resistance electric elements are used. This is why my heating bills were very high. I admit the newer, high efficiency ones would be better and not use resistance heat as much, but that is not to say that there are not situations where they would not be used. Also, the air source ones need to run a defrost cycle periodically to make sure the outside coil does not get an ice build-up. If one lives in an area where there is a lot of snow, then one would need to have a way to keep the outside unit sheltered from snow build-up so the snow does not block the airflow. Ground loops don't have those problems. 

In some areas, solar modules would work great. In others, subject to many days of overcast skies, solar might not provide much assistance. I grew up in western New York. We had plenty of cold, cloudy, snowy (lake effect snow belt) days where solar would not have contributed much. If these days were followed by sunny ones, then one would have had to go and clear the snow off the panels for them to do much good.

I would say that if the situation is such that air source would work, then go for it. If not, then ground source is a great option. It is also good for those scorcher days when the air temperature is hot since the heat pump would have a much cooler place to dump the heat from the house. That is the other half of the heating/cooling problem which has not been addressed so far in this topic.

Another option is a water-jacket wood burning furnace. It could be teamed with different backup sources for heating water to circulate in a hydronic heating system (radiators) or a water to air heat exchanger for a forced air system. I know people who have had such systems. Some use indoor water jacket wood burning stoves. Others have a system that is outdoors and so keeps the indoor air clean and free from smoke and the possibility of CO poisoning.
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Posts: 1067 		Post Options Post Options   Quote Pod People Quote  Post ReplyReply Direct Link To This Post Posted: 30 Oct 2022 at 10:22am

We have been in our house since we built it in1975.  The insulation at that time was not great, but adequate. We have gone through several heating system configurations since the beginning--all electric heat pumps, hydronic system, propane furnace and wood stove has been used. We currently have a good combination that serves us well.

 We live in a rural area with no natural gas available. So, we use a combination of electric, propane and wood for our heating needs. We have a Trane high efficiency dual fuel heat pump system (electric/propane) that is augmented by a jacketed woodstove with blower.

 Being in central NC, we use the heat pump(electric) most of the time.  Once the outside temps get to around 40-42 degrees, the propane furnace kicks in. We have five acres of woods, so we augment the heat with our woodstove.  In the depths of winter, we will use the woodstove almost every day during the daytime and it will usually die out around 3-4am. We use about 2 cords per winter that we cut and  split.

 Our combined electric/propane bills are reasonable for our square footage. However, as we both are approaching our middle 70’s, our wood usage will probably be declining in the future. We have a small tractor to move the logs, a hydraulic splitter for the wood and 5 acres of trees for wood supply.  The only issue is labor and energy in this case. So we have to assume that our actual cash heating costs will be increasing as we age.

 Travel often and safe

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Posts: 5290 		Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Posted: 30 Oct 2022 at 12:09pm
Originally posted by StephenH

Part of the problem is the frost level. I saw two types. One used a run that was bigger, buried so that the ground loop was wide and shallow. The other was deep and the loops were installed vertically. Those would likely work in the really cold climates. The need to dig deep for a horizontal loop would likely not be too much more than drilling for a vertical loop.

What makes the air source so much less attractive is that when the heat just isn't there to extract, pure resistance electric elements are used. This is why my heating bills were very high. I admit the newer, high efficiency ones would be better and not use resistance heat as much, but that is not to say that there are not situations where they would not be used. Also, the air source ones need to run a defrost cycle periodically to make sure the outside coil does not get an ice build-up. If one lives in an area where there is a lot of snow, then one would need to have a way to keep the outside unit sheltered from snow build-up so the snow does not block the airflow. Ground loops don't have those problems. 

In some areas, solar modules would work great. In others, subject to many days of overcast skies, solar might not provide much assistance. I grew up in western New York. We had plenty of cold, cloudy, snowy (lake effect snow belt) days where solar would not have contributed much. If these days were followed by sunny ones, then one would have had to go and clear the snow off the panels for them to do much good.

I would say that if the situation is such that air source would work, then go for it. If not, then ground source is a great option. It is also good for those scorcher days when the air temperature is hot since the heat pump would have a much cooler place to dump the heat from the house. That is the other half of the heating/cooling problem which has not been addressed so far in this topic.

Another option is a water-jacket wood burning furnace. It could be teamed with different backup sources for heating water to circulate in a hydronic heating system (radiators) or a water to air heat exchanger for a forced air system. I know people who have had such systems. Some use indoor water jacket wood burning stoves. Others have a system that is outdoors and so keeps the indoor air clean and free from smoke and the possibility of CO poisoning.


StephenH, you keep referring to the performance of the older air source technology. With all due respect,  please get an update. Look for example at the Fujitsu EXLTH mini splits. They operate efficiently down to around -15F. You and I will never ever see temps anywhere near that low. The ASHRAE 99% heating design temp where I live is 12F. That is the number HVAC professionals use to design heating system capacity. Yours is more like 20F. 

I just finished modelling the thermal performance of my house and an upgrade to my HVAC system, prompted by the tax benefits for new heat pumps, solar, energy storage, heat pump water heaters, and insulation in the IRA. A couple of those Fujitsus will heat my whole house. Compare that to the not so old Goodman central heat pump that was here when I bought the place 3 years ago, which craps out at around 35F, just as you say. 

There are modern efficient central heat pumps becoming available as well, but I think I'll go with mini splits personally. I like them because they are zoned, extremely quiet, and accommodate DIY installs. I've installed them before.  Outside North America residential central air is very unusual, everyone goes with mini splits. For good reason. 

I do plan to retain my central ductwork system and air handler though, so I can potentially install a wood based hydronic system as you are suggesting. You can no longer purchase a glass front wood stove with a water jacket (aka a water stove) in the US. These are very common in Europe. I found one on Craigslist a couple years ago and have it sitting in my barn. It combines the benefits of hydronic heating with fire  viewing (which we all seem to enjoy). I would like to connect it with a water thermal storage system and a water to air heat exchanger in my air handler. The storage system will allow on demand heating without needing to continuously fire the stove. Lots of technical and safety details to work out though  and insulated storage tanks aren't cheap...

As for solar, you would be right if we are talking about an off grid PV system, but no one does that if they don't have to due to lack of grid access. Residential solar nearly everywhere except Hawaii is net metered with an annual true up,  meaning that you are credited for summer production in the winter. 100% credit. So no need to match solar production with heat load. Forget pushing snow off the array.... The small difference in electricity consumption between a geothermal heat pump and a high efficiency air source heat pump system can be met far more inexpensively with a few additional PV modules. Personally, if I was in the geothermal heat pump business I would be thinking about how to transition out and into  solar and mini split contracting. 
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Posts: 5290 		Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Posted: 30 Oct 2022 at 12:15pm
Originally posted by offgrid

Originally posted by StephenH

Part of the problem is the frost level. I saw two types. One used a run that was bigger, buried so that the ground loop was wide and shallow. The other was deep and the loops were installed vertically. Those would likely work in the really cold climates. The need to dig deep for a horizontal loop would likely not be too much more than drilling for a vertical loop.

What makes the air source so much less attractive is that when the heat just isn't there to extract, pure resistance electric elements are used. This is why my heating bills were very high. I admit the newer, high efficiency ones would be better and not use resistance heat as much, but that is not to say that there are not situations where they would not be used. Also, the air source ones need to run a defrost cycle periodically to make sure the outside coil does not get an ice build-up. If one lives in an area where there is a lot of snow, then one would need to have a way to keep the outside unit sheltered from snow build-up so the snow does not block the airflow. Ground loops don't have those problems. 

In some areas, solar modules would work great. In others, subject to many days of overcast skies, solar might not provide much assistance. I grew up in western New York. We had plenty of cold, cloudy, snowy (lake effect snow belt) days where solar would not have contributed much. If these days were followed by sunny ones, then one would have had to go and clear the snow off the panels for them to do much good.

I would say that if the situation is such that air source would work, then go for it. If not, then ground source is a great option. It is also good for those scorcher days when the air temperature is hot since the heat pump would have a much cooler place to dump the heat from the house. That is the other half of the heating/cooling problem which has not been addressed so far in this topic.

Another option is a water-jacket wood burning furnace. It could be teamed with different backup sources for heating water to circulate in a hydronic heating system (radiators) or a water to air heat exchanger for a forced air system. I know people who have had such systems. Some use indoor water jacket wood burning stoves. Others have a system that is outdoors and so keeps the indoor air clean and free from smoke and the possibility of CO poisoning.


StephenH, you keep referring to the performance of the older air source technology. With all due respect,  please get an update. Look for example at the Fujitsu EXLTH mini splits. They operate efficiently down to around -15F. You and I will never ever see temps anywhere near that low. The ASHRAE 99% heating design temp where I live is 12F. That is the number HVAC professionals use to design heating system capacity. Yours is more like 20F.  There is always heat to extract, as long as the temp is above absolute zero, which cannot be reached anyhow ( 3rd law of thermodynamics). So the heat content of air at -15F is still 97% of air at 35F (if I did the math right). 

I just finished modelling the thermal performance of my house and an upgrade to my HVAC system, prompted by the tax benefits for new heat pumps, solar, energy storage, heat pump water heaters, and insulation in the IRA. Four little Fujitsus will heat my whole house. Compare that to the not so old Goodman central heat pump that was here when I bought the place 3 years ago, which craps out at around 35F, just as you say. 

There are modern efficient central heat pumps becoming available as well, but I think I'll go with mini splits personally. I like them because they are zoned, extremely quiet, and accommodate DIY installs. I've installed them before.  Outside North America residential central air is very unusual, everyone goes with mini splits. For good reason. 

I do plan to retain my central ductwork system and air handler though, so I can potentially install a wood based hydronic system as you are suggesting. You can no longer purchase a glass front wood stove with a water jacket (aka a water stove) in the US. These are very common in Europe. I found one on Craigslist a couple years ago and have it sitting in my barn. It combines the benefits of hydronic heating with fire  viewing (which we all seem to enjoy). I would like to connect it with a water thermal storage system and a water to air heat exchanger in my air handler. The storage system will allow on demand heating without needing to continuously fire the stove. Lots of technical and safety details to work out though  and insulated storage tanks aren't cheap...

As for solar, you would be right if we are talking about an off grid PV system, but no one does that if they don't have to due to lack of grid access. Residential solar nearly everywhere except Hawaii is net metered with an annual true up,  meaning that you are credited for summer production in the winter. 100% credit. So no need to match solar production with heat load. Forget pushing snow off the array.... The small difference in electricity consumption between a geothermal heat pump and a high efficiency air source heat pump system can be met far more inexpensively with a few additional PV modules. Personally, if I was in the geothermal heat pump business I would be thinking about how to transition out and into  solar and mini split contracting. 
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Posts: 1214 		Post Options Post Options   Quote mjlrpod Quote  Post ReplyReply Direct Link To This Post Posted: 30 Oct 2022 at 3:39pm
I use a pellet stove. I cant say enough good things about it. Mine is a Harmon fireplace insert. I never use the boiler in the house, unless I choose too. I burn nothing but douglass fir pellets and can go 2 weeks or more in the absolute dead of winter without emptying ash ashpan. Really good system, except you need to buy pellets. I don't have any neighbors saying " hey a pallet of pellets fell in my yard, wanna come get it?" 
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Posts: 6288 		Post Options Post Options   Quote StephenH Quote  Post ReplyReply Direct Link To This Post Posted: 30 Oct 2022 at 5:45pm
Yes, I keep referencing the old technology. It is what I experienced. I  did say this, "I would say that if the situation is such that air source would work, then go for it. If not, then ground source is a great option. It is also good for those scorcher days when the air temperature is hot since the heat pump would have a much cooler place to dump the heat from the house. That is the other half of the heating/cooling problem which has not been addressed so far in this topic."

I would have to see the newer ones in action. Mini-split systems might really be better, but the units I have seen hanging on the wall are not the most attractive things. It is, after all, a matter of choice. I choose to avoid heat pumps if I have a viable, cost effective alternative such as the natural gas heat and air conditioning package unit that we have. It might not be the most efficient, but it has been reliable except when the power has gone out. That is, however, rare and we do have the RPod to use if there is a longer outage.
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