Cantilevers are areas that protrude beyond your home’s foundation or lower supporting wall (e.g., upper floor bump out, bay window, room over a porch, etc.). The thin construction material found in cantilevers creates an ideal space for unconditioned outside air to infiltrate the home, and for conditioned inside air to escape.
Cantilevered spaces in homes create distinct energy challenges for homeowners. Unless special consideration is given to these unique construction features and their insulation requirements, you may suffer from cold temperatures and high energy bills.
Oftentimes, cantilevers are not air sealed and insulated. If the builder does insulate this space, installation of an air barrier is many times overlooked. Why does this space need both insulation and an air barrier? The space below a cantilever is shallow which does not allow it to meet local codes for R-value. Installation of a proper air barrier and insulation will prevent air infiltration by creating a thermal barrier.