Slab-on-grade Straight Edge Insulation, referred to as slab-edge insulation in the IRC, is one of the most under-used and often abused construction details. When done properly, it can add substantial energy efficiency and occupant comfort to the home. But getting it right can be a challenge for builders, and if not, the result is often sub-par. The graphic above illustrates what can happen if this detail is not implemented properly.
The images were produced by Lawrence Berkeley National Laboratory software called Therm, and provide a vivid demonstration of why this type of insulation is so important to the performance of the home. While these results are quite extreme, it is possible to see a visible gap of even a few inches between the slab and the frame of the house.
The Straight Edge Insulation Process: What Homeowners Need to Know
If you are constructing a new wood-frame home or retrofitting an existing structure, we recommend using a professional installer. However, if you do plan to install the insulation yourself, please follow the manufacturer’s instructions and safety precautions carefully. Dust masks and long sleeve shirts are a must, especially when working with fiberglass or mineral wool, and protective goggles should be worn when spraying foam-in-place insulation.
Foam-in-place insulation is injected into the walls of the home, either as a prefabricated (Structural Insulated Panel, or SIP) or sprayed in place by contractors at the job site. This type of insulation offers higher R-values than batt insulation, and it also forms an air barrier that eliminates the need for other weatherization tasks like caulking, applying house wrap, and vapor barriers. Foam-in-place insulation products and installation generally cost more than traditional batt insulation, but it reduces construction time and the need for specialized contractors.
Straight Edge Insulation
5248 Sultana Dr. 95301 Atwater CA
(209) 678 4276