In order to maximize the heat retention within a building and thus minimize any transfer of cold temperature into a building we have gone to great lengths to ‘break’ any contact between the two. At Friends School of Portland we installed 12″ (±R54) of rigid insulation in two 6″ thick staggered layers under the concrete slab to prevent any heat loss to the cooler earth temperatures below. Around the sides of the slab we installed 5″ (±R23) of rigid to do the same from a horizontal transfer of heat loss. This has a significant effect on the size of the heating and cooling system required and will pay back the added costs many times over during the lifetime of the building in lower energy costs.
