Earth coupled floors – high mass floors in contact with the soil below (slab on grade, tile, stone, CEB, earthen floors, salvaged brick) – are ideal for keeping homes cool in hot climates. They are not recommended for cold climates where underfloor insulation is best. Our earthbag roundhouse, which is in a hot climate, remains cool year-round due in part to the earth coupled floor. The indoor temperature is about 15 degrees F (8 degrees C) cooler inside than out, and the temperature remains nearly constant night and day. Plastic sheeting under the floor prevents wicking of moisture.
“Floors are often the primary link between the structure of a building and its foundations (the ground upon which it sits). Where floors are in direct contact with the ground, they can have a major influence on the internal climate by adding thermal inertia (capacitive insulation) which is assisted by thermal coupling with the mass of earth underneath the floor.
The coupling effect of the earth and building structure increases with depth. Walls and roofs can also be earth coupled if the structure is excavated below ground. Once a structure lies about 3.0 metres below ground, it has such great thermal inertia that it is no longer subject to day/night temperature swing, but only to slight effects from seasonal variation.”