If you're designing your own, build in a thermal mass:
http://www.consumerenergycenter.org/...n/thermal.html
As a person who aspires to be a survivalist, I would build a thermal mass that contains a large quantity of sealed water. It would act as a thermal mass while also giving you a huge emergency water supply.*
*Note that I have no idea if this is feasible or if you end up being a mosquito breeding ground, but it seems like it would be possible.