Alex Heath

Thanks so much, Matt! You've been a great help.

That looks to be a good bit cheaper than solid foam. How well does it breath? Are there any extra precautions to make installing it in an enclosed wood subfloor? Also, do you know of any suppliers that will do a bulk discount?

I also saw that Kelly Hart's foundation was just laid with some scoria. Does anybody have any knowledge of the thermal performance of such a foundation?

Hi all, and thanks in advance for the advice!

I'm currently designing an earthbag home with a rubble trench foundation and a high square footage (about 1700). I plan to do an earthen floor with a hydronic heating system embedded. The home will be built in climate zone 4A (coldish and moist), and I wanted to figure out a cost effective method of insulating under the floor. I looked into R-Tech by Insulfoam, but the cost for a high R value (35.5) is about $5/sq ft. I was thinking about using bagged rice hulls (R value of 3/inch) such as was done in this CoolBot project by HortCRSP and UC Davis in Uganda: https://naturalbuildingblog.com/diy-walk-cooler. Would this work if I built a wood framed subfloor and filled in between the boards with bagged rice hulls (along with probably some recycled cellulose or similar for moisture management)? This would be similar to straw bale walls, but I'm not sure if the boards will bleed heat (softwoods have an R value of about 1.4/inch). For reference, I'm shooting for a total R value of at least 30.

Thank you,
Alex