Building a Good Foundation

In the quest to build a better building envelope and more comfortable, cost efficient home the foundation is the least complex system to address because there are the fewest options.

Basements, crawlspaces and slab on grade foundations are often the lowest location of air entry in a home. Cold dense outside air pours into any opening to replace warm house air that leaves in the high parts of the house. The foundation, sill plate, and rim joist are all locations for air entry.

Basements and crawlspaces are subject to moisture from a variety of sources, high water table, poor drainage and condensation. Since foundation walls are permeable to moisture and can store moisture, basements can influence the relative humidity of the entire house. Concrete conducts heat much faster than wood and has a poor R-value of 5 for a typical 8" foundation wall. Therefore it is imperative to have quality insulation system and vapor barrier. The insulation system needs to create a “thermal break” to reduce the heat loss through the foundation and through the slab. While vapor barriers are required in most locations by code quite often they are inadequate, or poorly installed. By installing a superior insulation and vapor barrier system you minimize the ground contact that greatly effects the efficiency of your home, as shown above.

Insulation materials used in below grade enclosure applications are primarily limited to rigid extruded polystyrene board (XEPS) due to the need for high compressive strengths and moisture resistance. Extruded polystyrene board (XEPS) is more commonly known as blue board, though it comes in pink also. It has a very high R-value of 5 per inch of material along with it's resistance to the elements. For vertical wall applications, grooved insulation boards with applied geotextile fabrics can be used as a protection board for the waterproofing membrane and serve the function of a synthetic drainage layer.

Extruded polystyrene has a well established reputation for long-term reliability and superior resistance to the elemental forces of nature: time, water, cold, heat, and pressure. So while you can have a patented system installed from various manufactures you can also use extruded polystyrene board (XEPS) with a vapor barrier system.