There was thread in GQ recently on different types of Geo Thermal heating systems. I’m in the process of designing a home I plan to retire in that is located in northern Montana and I’ve been thinking about putting in the most cost effective system I can. While making sure my house is well insulated is obviously important, I have a number of options for how I would heat and cool it.
Some background… the house will be of standard construction, is 3,500 sf including a daylight basement, and is located 30 miles south of Glacier National Park. The winters are long and hard, with temperatures dipping into the minuses for weeks on end. They just had a late-in-the-season snowstorm there last week! The summers are nice and warm but it doesn’t ever get really hot, so heating is going to be the big issue with this house, not cooling. The petro fuel source is Propane, which is more expensive than natual gas but would be cheaper (I think) than using electric heat alone. Here’s what we are looking at:
Standard forced air heating and air conditioning, using propane as the heat source
Electric baseboard heating (I don’t think this really makes sense)
Radient heating which requires a propane boiler and coils runing underneath the flooring
Wood burning fireplaces… we have good supply of wood but at best this would be only be used to supplement our normal heating system
Geo thermal system, we could either dig an addition hole or run pipes on the property (we have almost 7 acres so space is not a problem). This would be used in conjuction with a forced air heating and ventilation system. If we went this way we would likly have to provide a propane heat booster to keep the temperature up where it needs to be (68 - 72 degrees in the winter). The system by itself should be great for the summer months.
I am willing to pay up front for a more expensive system if it means it will cost me much less to operate over time. For example, I was the first person on my block to purchase a hybrid car which is now much cheaper to run. The extra cost of the hybrid was paid for with gas savings after the first few years.
So given that whatever system we end up with will probably be running for most of the winter what would make the most sense? I like the idea of geo thermal, but I don’t know anybody that is using it where I currently live (in Northern California).
And while we will be on the grid, just in case we will have a solar assisted and/or propane generated power AC source so you can assume we will always have power for the pumps and fan motors etc.
I can’t comment on much other than to offer that a coworker of mine installed a propane heater with under-floor water-filled coils. She’s at 9000 feet in Colorado so it may be a similar climate to yours. 3600 sq foot house.
She’s chewing through literally hundred of dollars of propane per month. She wants to turn off a zone (she foolishly heated her garage floor) but cannot because of the inability to drain it. If she turns if completely off, the pipes will freeze and burst.
A different co-worker at a similar altitude (smaller home) swore by his wood-pellet stove for efficiency.
My own home, down here in the flats in Denver, has electric baseboard heat and it’s hard to control - no central thermostat, each room has its own. It does make it very easy to turn off a room, though.
All anecdotes but maybe a jumping off point for further research.
If you’re able to afford it, the GeoThermal system will be your best long term. Most heat pumps (and your geo will be a heat pump) need a source of backup heat. That is particularly true of a standard air source heat pump. The fact is, even a standard air source heat pump in Montana will produce heat cheaper than any other source.
The problem is that as it gets colder outside the amount of heat available to extract from the ambient air is less and less; precisely at the time your home needs more and more. So the issue is not whether a heat pump can produce heat economically. It’s whether it can produce enough heat.
A Geo system solves this by getting it’s heat from the earth below the frost line. Rather than trying to extract Btus from 0 degree air, it extracts Btus from 55 degree earth. While it is still common to have a source of backup heat, the geo will need it much, much less.
The upfront cost will be higher. But over the middle to long term you’ll come out way, way ahead. I can even post the math so you can do your own calculations.
FYI
There is often some confusion about economic efficiency and operational efficiency.
Electric heat—like baseboard heat—is extremely operationally efficient. (close to 100%) The problem with electric is that it is more expensive; it is economically inefficient.
If you have a cheap source of electricity (most of us don’t) electric heat may be good.