[stevehull]

Sam,

Sounds very nice. Being a dome, the ratio of surface area to volume is a minimum.

What you need now is to estimate how many BTU's per hour you need to heat your home. There are several ways to do this.

One way is to turn on a known amount of heat, during a cold night and see if the inside temp stays even. For this, you need to circulate air with fans, so there is a uniform temp.

For example, if a propane furnace of 36,000 BTU (36 kBTU) on 100% of the time keeps the house at a constant 65 on the coldest of winter nights, then you know the answer (36 kBTU/hr).

If the cycle time of the same furnace is 50% (1 unit of time on, 1 unit of time off), then you need 18 kBTU/hr. If your cycle time is 25% (1 time unit on, 3 time units off), then you need 9,000 BTU/hr.

You need a COLD night and get up at 4 am to record on and off times of heater when it is coldest. Do this quickly while you still have cold nights!

Very hard to do with a pellet stove as the heat output is not a known (but just estimated).

Then you know the size of any heating system for your local conditions (geothermal system or whatever).

Ask your local electric utility of they do a free energy audit. Get one and let us know. There are, sadly, ALWAYS tiny air leaks that really add up. Hopefully, they will do a blower door test that accurately measures the "tightness" of the envelope.

Our first, and collective advice is to button up, insulate up. Sounds like you have foam insulation (how thick?) , but the air infiltration remains an unknown.

Monies returned by reducing losses are FAR greater than any energy device be it GSHP, solar, whatever.

Welcome to the site.

Steve