Why is the envelope so important on a new construction with a geothermal system?
I live in MN. The code is R-19 in the walls. Some have indicated that to have geothermal the walls should be insultated with nothing less than spread foam, or better, build with ICF. Upgrading to spread foam insulation is twice the cost of R-19, which takes lot longer to get your return on investment which no one seems to be factoring in.
The type of insulation is not as significant as the air seal.
- You live in MN, so you know how well a good ski jacket can perform.
- But you will still freeze to death while wearing one if you don't zip it up!
If you can achieve a sealed envelope, the type if insulation you use takes on less significance.
- Go for the best seal and the highest R-Value.
- Foam in Place is an easy way to get the seal and R value, and has therefore become easy to recommend.
- Products that seal the framing from the inside to the shell of the house, followed with fiberglass work equally as well.
Geothermal is a high efficiency electric heat pump. Better than an air based heat pump, but still an energy user.
Any watt you save is a watt you don't pay for.