Slab-on-Grade Foundation Best Practices

On-grade foundations are a popular design in Interior Alaska. This project uses modeling software to address these questions:

  • A shallow frost-protected foundation  relies on heat loss to the ground to keep the soils beneath the footing above freezing. What’s the optimal amount of subslab insulation to use to achieve this goal while maximizing energy efficiency?

  • The Design Guide for Frost-Protected Shallow Foundations (prepared by the U.S. Department of Housing and Urban Development) is based on the assumption that the bearing surface of the building foundation is uninsulated in order to maintain heat flow into the soil.  What is the energy loss due to this strategy?  Alternatively, what is the right amount of insulation that could be used beneath the foundation bearing surface that both saves building energy while maintaining frost-free soils beneath the bearing surface?  

  • How much “wing” insulation do I need to use if I increase the amount of subslab insulation?

This project will help builders evaluate the most cost effective, energy saving, and safe insulation options for under the slab. A resulting online calculator will help builders and homeowners make decisions about foundation insulation.­

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Projects

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Designs for Rural Alaska Walls Monitoring CCHRC demonstration homes for efficiency and moisture infiltration several years after construction.
Structural Insulated Panels Structural Insulated Panels (SIPs) are prefabricated building materials used in residential construction in Alaska. This project prepared resources for homeowners who want to learn about SIPs, where they are used in cold climates, and considerations for Alaska.
Safe Effective Affordable Retrofits Testing a new batch of wall systems that can provide affordable retrofit options.
Energy Recovery Ventilators (ERVs) in Cold Climates Energy Recovery Ventilators (ERVs) are whole house ventilation systems that exchange stale indoor air with fresh outside air, recovering both heat and moisture from the indoor air to save energy. They have the potential to improve indoor air quality in a cold dry climate like Interior Alaska.