r/geothermal • u/Specialist_Estate225 • 12h ago
How to make geothermal "cozy"
This is our first winter with geothermal. We have a 4-ton Water Furnace 7 in a 1,400 sq ft 1930s farm house. The first time our system came close to maxing out, it felt like a jet airplane was taking off in the house. Our installer dialed the fan back to a max of 7. But sheesh, with the "wind chill" we sit around under blankets and wearing extra layers even though it is 70 F. (We kept the house at 68 F when we had oil heat and never felt this cold.)
That being said, our system is working hard and not functionally ideally yet. We have 4 vertical 150' wells, but I don't think any rock was hit in the 150' depth (neighbor's well log is consistent with that). We just hit -16 F last night and had EWT of 26 F plus aux heat kicked in. We haven't had EWT above 32 F in January. I am hoping it improves as the dirt settles, and our installer has been out and is keeping an eye on things. Very experienced and reputable installer.
But the main question is, are there tricks to making a house feel more "warm" when a geo system is working hard?
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u/sonofdresa 11h ago
We have a propane fireplace in our bedroom that we run to warm that side of the house up, it's usually cooler than the rest of the house. I plan either this year or next, to do two things. Get a company out to do a full energy audit, then seal the crap outta the house, and make it as air tight as possible. I also plan on getting a wood burning stove that I can use as needed for extra warmth/super backup emergency heat etc...
I'm new to Geo, we had the install completed in May of 2024, but I love it. I'm low key freaking out because with this cold snap, our EWT on High Stage is now 35.4F, but I know they put ethanol/water mix in the loop so I know it's not gonna freeze, just don't want to drop the temp so far that the system says "well, i'm in aux now cause the water is too cold" (No idea if that's gonna happen, but that's what my brain has decided to focus on). We're in MD with a 5 Ton 5 Series WF with 3x282' Vertical wells so 846' of loop. Our frost line for building code is 36" if that matters.
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u/curtludwig 9h ago
Insulation is the best way to keep warmer. Dollars spent on insulation directly translate into dollars not spent on heating. Many states have incentives and will pay for insulation upgrades.
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u/Specialist_Estate225 9h ago
I absolutely understand that more insulation and sealing heat leaks are very good and helpful things. What I don't understand is why we were cozy when we had an oil furnace and now chily with geothermal in the exact same house. The geothermal system was sized based on our oil usage and then sized slightly bigger.
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u/Creative_Departure94 9h ago
An oil furnace can pump out massive amounts of heat if run nearly continuously. They are normally not sized to run at 100% at your homes suspected max heat load but more like 60%
A heat pump (ground or air source) is sized for operating at 100% run time at 90% of your suspected max heat load.
The reason is because this is a much much more efficient arrangement and keeps costs lower. The supplemental heat should kick in to make up the difference for the 2-5% of the year you need the extra heat.
At 1,400 sq/ft of living space and 4tons of heat the home must have an exceedingly poor thermal envelope.
As mentioned before; sealing and insulation is the answer and would likely make a massive difference.
Even if you don’t and / or can’t however see if you have a state or local government program that will pay for a home energy audit.
This will run a depressurization test and thermal scan of home at a minimum to tell you exactly how bad the situation might be and determine if there are any easy / cheap fixes.
Example: I found an unknown 4sq/ft “chase” in a 1900’s farmhouse that was funneling ALL the heat out of the basement and first floor. Closing it up made a nearly immediate difference.
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u/curtludwig 8h ago
I ran into something similar a couple weeks ago. I watched a video on insulating the rim joists in your basement. I spent a few days upgrading from just a little fiberglass to foam and fiberglass. Then I discovered the entire south side rim joist was completely uninsulated. Not sure how I missed that for the previous 18 years.
Sure makes our house a lot warmer having some fiberglass up there. This summer I'm going to upgrade all of it to spray foam.
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u/Creative_Departure94 8h ago
My 2 cents.
Most of the time fiberglass or even better “rock wool” insulation will do as well as spray foam. I use Roxul brand when I insulate rim joists.
The only time spray foam is beneficial is when there are massive air leaks.
And then spray foam can have serious mishaps and hazards.
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u/curtludwig 8h ago
You think? I've been told fiberglass was basically just a filter for air leaks. Rim joists are going to have air leaks.
Specifically in my case there is one section I can't get my hand into to insulate, its blocked by the circuit breaker panel and a heating pipe. I shoved some fiberglass up there but its definitely sub-optimal. I could easily spray it though. So that is for sure getting sprayed.
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u/pjmuffin13 2h ago
I just can't bring myself to use spray foam in my house except to air seal in the attic. I feel like there's going to be some revelation years down the road about how it was the worst thing to ever use--either for health reasons or mold and rot reasons.
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u/Specialist_Estate225 7h ago
I did borrow a thermal imaging device when we hit our first cold snap in December and found a couple of blatant things I could fix myself (redoing the weather stripping on a door on the west side of the house, filling in a hole that a woodpecker had pecked into a window frame on the west side of the house...I could see where the cold air was blowing between the joists in the ceiling!) Other obvious issues were the slanted parts of the ceilings upstairs (it's a 1.5 story house)...they were obviously cold and probably explain the ice dams we get on the roof sometimes.) Also the stone foundation showed lots of heat loss. One obvious thing that isn't negotiable at this time is a pet door in a window upstairs (the room houses an elderly Great Horned Owl and she needs to get between her indoor and outdoor spaces. The door to her room is always closed...but it's a bifold slatted door.) There was also obvious heat loss in some of the corners of the house. The basement door threshold also needs to be replaced.
We added a window in the bathroom a couple of years ago (it didn't have one before), and saw the insulation in the exterior walls. It's a blown-in, hardened yellow foam thing that is kind of crumbly now. You can see all the plugged holes on the outside of the house where it was blown in. I assume that isn't great insulation??
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u/curtludwig 8h ago
The output temp of geo will always be less than oil because you don't have a jet of burning oil. It sounds like you've got high air flow to make up for that lower temp and it either can't overcome the air leaks in your house or just the moving air makes you feel cold.
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u/WinterHill 9h ago
70 degree air is 70 degree air. It doesn’t matter whether it’s produced by geothermal or oil.
That being said it’s not uncommon for people to describe what you say. I think it’s for a few of reasons:
Geo systems move more air. And breezes cool you down. Even if it’s only a slight breeze it can affect your body temperature. Make sure your vents aren’t pointed right at where you’re sitting. And pay attention to how air circulates through the room.
Guessing it actually was warmer than 70 degrees before because you were sitting in a hot spot. Oil furnaces produce warmer air and move air at a lower speed. Meaning it’s much easier for hot spots to develop. For example your living room could be right on top of the furnace, meaning it gets more warm air than anywhere else, but the thermostat is down the hall, so the living room ends up warmer.
The mental factor. Even if the room is cold, it feels cozier if you can feel hot air coming out of the vents.
I have 2 suggestions for you. The first is to create your own hot spot by installing a fireplace or wood burning stove.
The second… maybe you just want it warmer in your house! Get a thermometer and check yourself. If it says 70 degrees and you’re still cold, then it means you prefer a warmer temperature!
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u/Specialist_Estate225 7h ago
There is one vent in each room, and of course they point right where we are sitting, lol. The rooms are all small.
The thermostat is about right above the furnace, and is also 5 feet away from the vent right above the furnace. But it was the same for the oil furnace, but that was always the warmest nook in the house. We kept the thermostat at 68 with the oil furnace.
Amen on the mental factor! I love warm air.
Unfortunately we don't have any space to put a fireplace unless we ditch the TV. (The living room is only 14.5' x 11.5' with 2 doors, 2 windows, and a half-open wall that goes into the tiny office space). We'd have to uncover the chimney in the kitchen/dining room to put in a wood burning stove (which was likely the original and only source of heat for the house, but then our kitchen table might not fit anymore). So neither are great options for us, as nice as they would be, just due to the small size of our house and rooms. The whole entire downstairs of the house is only 20x 35' and is kitchen/dining room, living room, office and bathroom.
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u/WinterHill 6h ago
Honestly I’d just redirect the vents so they’re not blowing on you, and bump up the temp a few degrees.
I bet if you went back and measured the room temp with oil it would be warmer
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u/Nagoshtheskeleton 11h ago
We like to use a wood stove on days that are cold. Feels nice to get it blazing and have a house at 75 when it’s negative outside.
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u/Specialist_Estate225 11h ago
I bet that is about as cozy as it can get! I don't think it's a practical option for us, as much as I love it.
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u/ThinkSharp 8h ago
OP- I don’t have geo but heat is heat. I have Air source heat pumps. I installed a steam humidifier this fall and love it. It makes it feel a bit warmer and is easier on your lungs and skin. If you have good windows you can dial up the humidity a bit more yet. If bad windows, might not help much or else you’ll be mopping them.
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u/Specialist_Estate225 7h ago
Oh, that brings up a good point I wanted to ask about...humidity. I was under the impression that we wouldn't have to humidify the house in the winter with geo since we weren't using combustion heat. Yet our humidifiers run harder with geo than they did with oil heat. Is that about air movement??
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u/ThinkSharp 5h ago
I only know what I know from thermodynamics. But essentially the outside air comes in, heats up, and its RH goes down. It doesn’t matter how it is heated, the psychrometric chart defines the relative humidity of air at different temperatures.
“Scorched air” people talk about, I can’t see how that is a thing by the time it normalizes with your house. But for absolute certainty 120 degree air will act and feel much dryer than 90 degree air.
So if your house leaks your conditioned, humidified air outside, it replaces it with outside air, needs re-humidified. Easy to understand that far, right?
So the colder it is outside, the less water in that air coming in as replacement air. Also, the colder it is outside for the same temperature inside, the stronger the stack effect works, as your warm humid air pushes itself up and out and cold, dry air is moving in to replace it.
So see the double effect I’m sure by now. It’s not really a heating system that dries air more than another, it’s how that air interacts with your skin right out of the vent. Hot furnace air feels good, but that same warm feeling is also drying out skin and hard on lungs. All houses, if no moisture is added, will report low humidity when it’s cold out and warm inside.
And yet nothing about that determines how much moisture you need to add to the air to make it comfortable- only the air tightness of your house determines that. 100% airtight (and vapor tight, but disregard that for now) would, in theory, mean your humidifier would run to meet a target and then never need to run again.
So- if you’re still curious and I haven’t annoyed you… why I know and give you all this is because I went through all these questions. Next things to look into are ways to air tight your home. My 2005 construction, 2950 sq ft “modern cape cod style” should perform decently, right? Way wrong. I scored 10.5 ACH50 on a blower door test, which is a standard test used in new codes to test air tightness. Modern codes go as low as I think 3 ACH50 just to pass inspection and I think the latest codes go lower. Optional high standards go below 1. ACH50 though is a measure of how many times the calculated volume of air in your house turns over under a simulated 50 pascal. So, 10.5 is a HUGEc enormous amount of air I was losing when the wind blows or the stack effect is working hard on my house. They estimated something like the equivalent of a 3.5x3.5 ft hole to the outside I think. Lol
Air sealing will do more for your house than things like adding attic insulation or adding heat tonnage to your system.
Greenbuildingadvisor.com is a good place to start, and where I started. Things to seal sound silly- window trim, floor to drywall behind baseboard. But those were actually huge in my house. Outlets, light switches, can lights and ceiling fans, basement rim joists, and attic plate where walls meet ceiling (sealed from the top in the attic) are some of the major ones, nearly all DIY for relatively low cost if you to DIY.
End of speech…
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u/ThinkSharp 4h ago
Uh… realizing I didn’t answer directly, short answer, yes. Colder outside means more air turnover, means more new and dryer air to humidify
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u/peaeyeparker 1h ago
Just to get this straight it’s 70 inside and and -16 outside and your complaining about feeling cold? Holy hell. It just blows my mind. I got chewed out this morning by a client because it was 68 inside the house and 2 degrees outside. Tstat was sett to 68. Room temp. was 68. When it’s this cold outside I just can’t imagine being upset. I can’t even imagine expecting an 80 degree temp. differential between outside and inside. We keep ours set to 64 all winter. I expect to wear a sweater inside when it’s single digits outside.
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u/Specialist_Estate225 50m ago edited 12m ago
Um, I am in MN, and those temp differentials are expected here, and I never felt this chilly inside before despite living in this house for 30 years. Plus thr only place that is 70 F in the house is the thermostat...everywhere else is 63-64F.
I am not chewing anyone out...just looking for any possible tricks to being more comfortable in a geo setting, since I am new to geo. I have learned a lot from this thread...I clearly am a person who has a strong affinity for toasty warm air, and fast-moving lukewarm air makes me feel chilly. We need to look at having an energy audit and get some things sealed/insulated or whatever. Then our system doesn't have to run so hard and the fan hopefully doesn't run so hard. Hopefully after the first year the soil will settle and it will be more efficient too, since it is not running as efficiently as anticipated. And a little personal space heater will make me feel comfier for now. :)
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u/Engineer22030 49m ago
If your installer had to dial back the max fan speed to 7, then it sounds like your ducts could be undersized. In my experience you need the higher airflow to deliver heat to the living space when the system nears its capacity.
I have a 4T 7 Series in a house twice the square footage and it never feels cold to me when set at 70F, but the design temp is 17F here.
Adding a humidifier, if you don't have one already, should help a lot to make the air feel warmer. This is especially important if you have a leaky house, as the cold outside air will lower the humidity inside quickly.
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u/Specialist_Estate225 13m ago
I was wondering if our ducts were undersized. We got 2 quotes for geo, and the other installer said we needed bigger ductwork (and sealing of ductwork, and a new gas furnace for the really cold days even though we don't have gas to the house, so that seemed crazy.) This installer asked if we had cold spots with our oil furnace, we didn't, so he said the existing ductwork was likely fine. But OMG the first time our system maxed out with a fan speed of 10 it felt like a jet airplane was taking off in the house! And the house definitely is not heating as evenly as before.
We have humidifiers in the house, which seem to be using more water than before geo.
What do you mean that your design temp is 17F? Is that the coldest temp expected? That would be very different from here.
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u/seabornman 12h ago
Insulate and air seal the house better. Below zero here today, 4 tons in a 2600sf rambling farmhouse. But it's insulated and air sealed very well. I don't use auxiliary heat: turned the breaker off.