As to using pumice or perlite in a cementitious mixture, everything I have read would seem to indicate that as soon as you fill those air spaces in the rock with the cement slurry, you lose the insulating quality of the material. I was really bummed to keep reading this over and over on the net. I do think that your climate makes a difference, and that in some places you can get away with it better than others. We built a 16' ID catenary dome tank house for
water filtration equipment from scoria bags, and then had it coated with 3" of shotcrete inside and out. Even in our severe climate, it takes only a
light bulb to keep it above freezing. There are no windows for solar gain, and two 6" vents that are open year round to reduce humidity levels. I do not think we could have gotten this kind of performance if we had used pumice-crete (the first choice). Just my 2 cents-
We are in the planning stages for a house. We are almost set on a modified post and beam frame with one inner row of earthbags and one outer row of scoria or perlite. The bags would be contained within the framework. The walls would be plastered with a vapor permeable earthen plaster. This seems to be the best use of both mass and insulation. It will certainly take longer, but we have adjusted our expectations to fit a good outcome, even if it takes more time. I don't know how much time your
project is worth.