What is the roll of airspace when using HeatBloc-75?
To function effectively, a radiant barrier must face an airspace of 1″ or greater. A radiant barrier will not function if sandwiched between two solid surfaces. HeatBloc-75, when installed on the underside of roof decking, normally faces downward into the attic. If insulation is installed in the cavity formed by the roof trusses and the roof decking (as in a cathedral ceiling), at least 1″ should be allowed between the top of the insulation and the HeatBloc-75 surface.
