This knee wall space was insulated with Foamax Insulation board. The superior R-value and a foil face on the outside reflects heat out in summer. Foamax™ has a class A fire rating and can be left exposed to living area without a thermal barrier. No harsh chemicals are sprayed in your home, like spray foam. The attic is now part of the con-ditioned space in your home, and ducts in the attic are no longer in a hostile environment.