I am planning on installing a radiant barrier in my attic and garage door. I read all over that radiant barriers and reflective insulation “must always be installed in the presence of an air space.” However, I have a few questions regarding that air space:
- How big does the air space have to be?
- Do you need air space on both sides or only one side (if only one side, which side is best)?
- For the garage door, can I install insulation first (directly against the aluminum garage) and then attach the radiant barrier to the insulation? Again, I think this relates back to airspace, does the inside of the garage act as airspace or does the insulation?
- When you install the radiant barrier on the underside of the roof rafters, the large air space it faces meets the requirement.
- The most effective application has the reflective side facing the attic air space. In this application there would be an airspace on both sides.
- Assuming you plan to leave the reflective side facing the inside of the garage airspace, that is all you need to do.
In answering your questions, I am assuming you are planning to install the radiant barrier according to the best practices method endorsed by RIMA. If you are planning another method, you might want to specify and I’ll respond.