Daniel Schmidt wrote:One really interesting example of an insulator is in this video below
About a year ago I actually made some carbon foam after watching that video. I used a biscuit tin with a small hole punched in the top, put some bread slices in it, and threw it in a camp fire. It actually worked. It was just for fun though.
I'm not a builder - but I believe the thing about insulation is that if you don't do it properly, you may as well not bother at all.
Daniel Ray wrote:Glass bottles are frequently used underneath cob ovens for insulation and would probably work for an earthen floor.
Bottles are somewhat suitable for clay ovens because solid glass has a reasonably high heat tolerance which is an important consideration for ovens. You don't need that characteristic in a floor. Solid glass is actually a terrible insulator - about the same as solid cement according to
this site I just found. Glass bottles will have a lot of thermal bridging around the walls of the bottles.
Has anybody got scientific test data on glass bottles set in clay? I very much doubt it, and my hunch is that it is not worth the time and labour invested.
The small amount I do know about insulation is that it's all about SEPARATION of materials and restricting the movement of air. You want as little physical contact (bridging) between the ground and your walking surface. There's a reason why cavity-brick walls are two skins of brick with almost no contact between them - that achieves the separation. Then fibrous insulation stops the convection currents in the gap.
Aaron Tusmith wrote:I am painfully ignorant but isn't compaction an issue when insulating under an earthen floor?
Yep, you definitely can't use materials that are both load-bearing and susceptible to settling. That will be a disaster.
@Daniel: From the link you posted:
Irene Kightley wrote:The insulation has been fantastic, cool in summer in warm on bare feet in the winter when the stove is on and when the winter sun heats the mass up during the day.
I believe the above comment is conflating two different characteristics. Cool-in-summer and warm-in-winter is a characteristic of high thermal mass, not high insulation. High insulation feels warm all-year-round.