I live in zone 9 (South Louisiana). Can you tell me what radiant barrier or reflective insulation I would benefit from? It would be installed in an existing attic space that houses my A/C ducts. I’m confused and would appreciate clarification if possible. It is my understanding per the Department of Energy “reflective insulation and barriers must have air space adjacent to the reflective material to be effective.” Per Reflectix (sold at Home Depot and Lowes), I should staple the reflective insulation directly to my roofing deck.
Stapling Reflectix directly to the underside of the roof deck would be acceptable. But, a more effective way would be to staple Reflectix or a thin radiant barrier to the underside of the roof rafters. Doing it that way would cover all the wood and would be more effective. As to the issue of an air space where the Reflectix was installed against the roof deck, the air space of the attic itself qualifies. That said, the preferred application is to the underside of the rafters.