I live in south Alabama (Mobile) and recently purchased a home that was built in 2003. The AC unit is in the unconditioned attic, and I have soffit vents and an electric power vent near the ridge. In spite of these, the attic temperature is quite extreme on a 90-degree day, approaching 125 degrees ambient, and I measured a few rafters in excess of 138 degrees.
I have no radiant barrier at this time, and it appears I am an ideal candidate. However, the attic is very tall and at a 12/12 pitch. This would require me to use a very tall ladder (10′ or so) in a crowded space.
Researching potential solutions, atticfoil.com has a suggestion to build a “flat top” and simply drape the radiant barrier over the top of the supports. This appears to be similar to simply draping it over the trusses in an engineered truss system. Does the fact that it will no longer be perpendicular to the angle of the radiation, will it reduce performance? I guess the real question I’m asking – should I go to the trouble of fighting with a ladder in the attic (and all the attendant dangers) or will a flat top/draped solution work just as well?
It seems to me that building a tent like structure is pretty extreme, but since I can’t see your application, it may be a workable option. As to the orientation of the radiant barrier, that won’t have a negative effect on its’ performance.
Since applying the radiant barrier to the roof rafters seems like a major task, you might want to consider another option — RIMA suggests with reservations, to lay the radiant barrier directly on the floor. If that would work for you, remember 2 things:
- Dust can accumulate on the top surface over time and will degrade the performance. You’d want to keep an eye on this and if you already have a dust issue in the attic, you might consider scrapping this idea. Otherwise, keeping the surface relatively clean would be an important task.
- Make sure the AC is covered with radiant barrier. That will have a major impact on AC running times and resulting energy bills.
My answer to your question of the value of a radiant barrier in your home is that it would have a significant impact on energy costs during the hot months of the year.