The thermal mass of the concrete floors combined with the very high insulation values of a straw bale home make it an excellent choice for radiant floor heat. The cost of a radiant system in straw bale home is very low, often no more than a water heater, a circulating pump and a couple hundred feet of pex tubing.


Solar can be used to supplement the heater in a home of such low heating demands.

PLACE THE INSULATION IN THE FORMS AND POUR THE CONCRETE
THE INSULATION WILL BOND PERMANENTLY TO THE CONCRETE

http://www.energycodes.gov/support/slab_faq.stm

IMPORTANT INFORMATION: in areas that are prone to termite problems use foam insulation that is termite resistant.   


STYROFOAM™ BLUEGUARD™Termite Resistant Insulation