From the outside

• Insulate the outside wall exactly as described previously for the outside basement wall (see Figure 6-22 and Insulating the basement from the outside).
• If outside obstructions (e.g. a porch or paved driveway) make it impossible to completely encircle the crawl space from outside the house, then insulate the inside portion of the wall at those points. Overlap interior and exterior insulation coverage by at least 610 mm (24 in.) See Figure 6-11.
• If the crawl space does not open into a full basement, it should have some form of ventilation. In general, do not use vents that open to the exterior, as there is a risk of condensation increasing during the summer. Instead, try to incorporate the crawl space with a whole-house ventilation approach or consider using a dehumidifier. Any existing vents should be sealed permanently if you are performing a full renovation where the space will be heated.
• If the foundation footings are above the frost line, insulate on the outside of the crawl space walls. By insulating on the outside, the walls will be kept warmer, avoiding the possibility of frost heave. Shallow footings can be kept warmer by placing a layer of horizontal insulation sloping away from the foundation.

From the inside

• If using rigid board or spray foam insulation, follow the approach as outlined for the inside of a basement (see Insulating the basement from the inside). Treat joist spaces as described in How to frame and insulate inside the basement. Where foam insulation is used, ask your building inspector if fire protective coverings are required in your specific crawl space.
• Apply a polyethylene moisture barrier to the crawl space floor and ensure the space is adequately ventilated as noted in the third bullet of How to insulate a heated crawl space, From the outside.