Passive Geothermal Heating and Cooling in the Straw Bale House
The Strawbale House takes advantage of the natural heating and cooling abilities of the earth.
The building is one level on a floating or bell slab. We did not insulate under the slab, since we felt that this would cut us off from this natural heating and cooling. Instead we used 2 inch rigid foam insulation on the vertical sides of the foundation slab, than we used 4 foot by 8 foot sheets of rigid foam, butting them up tightly length wise to the bottom of the foundation at a downward pitch for drainage.
This created a 4 foot insulation barrier around the foundation called perimeter insulation. This helps capture the natural 55 degree F ground temperature in winter and creates what is called a heat sink in summer to naturally draw heat out of the building. We also believe the perimeter insulation helps prevent winter frost heave.