Re-thinking geothermal

[ametcalf]

An interesting thread that I would like to add my two cents to. We built a high performance home with geothermal in 2008. Before and while we were building I went to the same seminar 5 times and learned more every time I went. I will try to compress a 3 hour seminar into a few paragraphs.
This thread has focused almost entirely on the heating system but you have to consider the whole house as a system and all the components of that system have to work together. From reading your posts I believe you did a great job of building your house to make it efficient. But things have changed since 1992. The first thing I would do before I even started thinking about what type of HVAC is to run a blower door test on the house and tighten it up. Last winter I spent a couple of weeks tightening up the house we moved from when we built our new house. It is a hundred years old and not as well constructed as your house but by using great stuff foam in every crack and opening I could find, putting foam plates behind the outlets and switches and other measures we cut the heating bills about in half and made the house more comfortable. Wish I had done it 30 years ago when we bought the place. What the blower door test on that house told us was that we had more air leaks from outlets on inside walls than the outside walls. When I went to the attic and pulled back the 12+ inches of fiberglass I saw where the air was coming from. The holes where plumbing and electrical penetrations were made were allowing a free flow of air every time the wind blew. After tightening up the house the next step I would take would be to get someone to run a GOOD J-manual calculation on what your heating needs really are. The reason I emphasis GOOD is that we had 2 contractors bid on the geo thermal on new house. One calculated that we needed a 4 ton unit and the other calculated we needed a 2.5 ton unit. The first guy obviously kept hitting the default button on his computer. The second company actually came and measured the windows, checked the type construction, (sips), looked at the north south orientation of the house, etc. They calculated that we needed a 2.5 ton unit but they installed a 3 ton unit because they said they just couldn't bring themselves to install 2.5 tons in a house this size. They didn't know how tight the house was going to be when we got done. As it worked out 2.5 tons would have been better. In fact, after living through 2 winters in this house I think a 2 ton unit would have been fine as we never go off stage one in a three stage system. The fact that your oil furnace is only running 12 to 15 min per hour in sub zero weather tells me that your present system is oversized. An oversized system is less efficient than a properly sized one. An analogy would be a car that races from stop light to stop light and waits for the next green light as opposed to a car traveling at the right speed to stay in sync with the traffic lights.
Our geo thermal uses 3-200 wells. Wells are relatively cheap here because we are sitting on solid limestone so they don't have to put casings in the wells. We are heating and cooling our 3000+ square feet for about 83 cents a day.
I hate to make this post any longer, if you are interested pm me and I will send you my phone number and I will be glad to talk to you.
ametcalf

 

[Rob-D]

If it wasn't for everything else being affected by the oil price, I'd agree with the sentiment.

Sean

Sean,
I agree, that's why I said "almost".

 

[Rob-D]

An interesting thread that I would like to add my two cents to. We built a high performance home with geothermal in 2008. Before and while we were building I went to the same seminar 5 times and learned more every time I went. I will try to compress a 3 hour seminar into a few paragraphs.
This thread has focused almost entirely on the heating system but you have to consider the whole house as a system and all the components of that system have to work together. From reading your posts I believe you did a great job of building your house to make it efficient. But things have changed since 1992. The first thing I would do before I even started thinking about what type of HVAC is to run a blower door test on the house and tighten it up. Last winter I spent a couple of weeks tightening up the house we moved from when we built our new house. It is a hundred years old and not as well constructed as your house but by using great stuff foam in every crack and opening I could find, putting foam plates behind the outlets and switches and other measures we cut the heating bills about in half and made the house more comfortable. Wish I had done it 30 years ago when we bought the place. What the blower door test on that house told us was that we had more air leaks from outlets on inside walls than the outside walls. When I went to the attic and pulled back the 12+ inches of fiberglass I saw where the air was coming from. The holes where plumbing and electrical penetrations were made were allowing a free flow of air every time the wind blew. After tightening up the house the next step I would take would be to get someone to run a GOOD J-manual calculation on what your heating needs really are. The reason I emphasis GOOD is that we had 2 contractors bid on the geo thermal on new house. One calculated that we needed a 4 ton unit and the other calculated we needed a 2.5 ton unit. The first guy obviously kept hitting the default button on his computer. The second company actually came and measured the windows, checked the type construction, (sips), looked at the north south orientation of the house, etc. They calculated that we needed a 2.5 ton unit but they installed a 3 ton unit because they said they just couldn't bring themselves to install 2.5 tons in a house this size. They didn't know how tight the house was going to be when we got done. As it worked out 2.5 tons would have been better. In fact, after living through 2 winters in this house I think a 2 ton unit would have been fine as we never go off stage one in a three stage system. The fact that your oil furnace is only running 12 to 15 min per hour in sub zero weather tells me that your present system is oversized. An oversized system is less efficient than a properly sized one. An analogy would be a car that races from stop light to stop light and waits for the next green light as opposed to a car traveling at the right speed to stay in sync with the traffic lights.
Our geo thermal uses 3-200 wells. Wells are relatively cheap here because we are sitting on solid limestone so they don't have to put casings in the wells. We are heating and cooling our 3000+ square feet for about 83 cents a day.
I hate to make this post any longer, if you are interested pm me and I will send you my phone number and I will be glad to talk to you.
ametcalf

Nice house!
Thanks for the input too.
This house is so tight that I have to open the front door sometimes to get the Tulikivi fireplace to vent properly. In fact it's mouse proof. The ceiling in the great room is over r55 and the walls are little low at r22.5 or so. The outside of the basement concrete walls are insulated also so it doesn't take much to get this place hot. The oil fired furnace I'm now using is about the smallest I could get to run the place efficiently. I know what you're saying when I called a plumbing firm to give me an estimate for a boiler they came in twice the size of the one I installed!
I'll send you a PM and perhaps we can chat a bit, thanks for your help,
Rob

 

[Rob-D]

When we build our house there was not water in the pond to speak off. The coils were about half above the ice. I measured the water temperature in the inlet of the HP to be about 26F. Nevertheless the heat was working fine whole winter. The pond water temperature is not the whole story. The pipes between the pond and the house will also extract some heat from the ground.

Ladia,
That's interesting, how far is the pond from the house and how deep are the lines from the pond?
Rob

 

[SpringHollow]

If it is that tight, it is not safe to run a combustion device, etc. You need to install an air exchanger.

Ken

 

[Kyle_in_Tex]

I've only lightly perused this thread and it got me to thinking (dangerous thing eh?). At what point in $$$ does it make sense to go to solar PV panels and forego a geothermal? It would seem a large enough solar grid tied into the main grid where the meter turns backward when consumption is low might be an answer. As the costs of PV comes down, it looks better and better. I'm not knocking the geothermal as it makes sense for some who's costs of installation are not that high.

Here in the south, our summer power needs are greater than our winter needs, mainly due to duration of season and not temp differentials. IE, my summer bills stay high for 4-5 months and my winter bills are usually high for about 2 months.

Here is a neat solar calculator link I've discovered.

Kyocera | Solar Energy Products | Products | Tech Support | Kyocera Solar PV Calculator

I will look for a solar panel re visited thread.

 

[Chilly807]

I think solar won't generate enough heat during the winter months at our latitude, when you need it the most it works the worst. I.e. short daylight hours and frigid temperatures.

If you had a big enough solar grid it would do the job, but I have no idea what it would take. No one here is doing that, to the best of my knowledge, so it's most likely cost prohibitive.

Sean

 

[DAY]

Last winter I spent a couple of weeks tightening up the house we moved from when we built our new house. It is a hundred years old and not as well constructed as your house but by using great stuff foam in every crack and opening I could find, putting foam plates behind the outlets and switches and other measures we cut the heating bills about in half and made the house more comfortable. f

Hundred year old houses (mine was built in 1781!) are not a health problem when "tightened up", but new construction can be. Reason: All the synthetic building materials, from vinyl siding to carpets, will outgas nasty stuff (like formaldehyde) for years.
Anyone recall the horror stories a couple of years ago, about Chinese drywall? Or radon? In this area (eastern PA) it comes up from underground, and in a tight house has no where to escape. It was discovered by a worker at the Limerick power plant, who set off a radiation detector on his way INTO work!
Cracking that front door proves that the house is tight- but carbon monoxide will get you if that stove can't get outside air!

As was said above, the whole picture needs to be taken into account when planning an energy efficient house. Even Jimmy Carter's advice to turn down the thermostat, and put on a sweater:laughing:

 

[ametcalf]

Hundred year old houses (mine was built in 1781!) are not a health problem when "tightened up", but new construction can be. Reason: All the synthetic building materials, from vinyl siding to carpets, will outgas nasty stuff (like formaldehyde) for years.

You are exactly right. Our heat recovery unit runs when our heat pump runs. In the spring and fall when the heat pump is not running if we don't open the windows I wake up with a headache. We have very little carpet, lo VOC paint, and Ikea cabinets which I think have about half the formaldehyde of some American built cabinets. We were aware of the dangers of building a tight house so we tried to select products that would minimize the off gasing problem and we have no combustion appliances in the house. We still need to make sure that we are getting outside air into the house.

 

[tractordog]

ametcalf

Thanks nice right up.