Radiant Barrier

[adambeazley]

A Radiant Barrier([url]www.raflect.com[/url]) is basically an aluminum foil sheet product that is generally applied to the bottom of the roof rafters to reduce the amount of radiant heat entering into the attic. In southern areas from TX to FL they are VERY effective and quite cost effective as well. They will keep your attic space much closer to the outside ambient temperature, thus reducing the load on your AC.

coastal chic, below mentioned that foam-sealed attics are the best and while I really do like foam, the costs are very high. Radiant barrier is about 12 cents per sq foot versus $2 to $2.50 per sq ft for foam. I disagree with her in that a rip in a radiant barrier makes it not work, that just flat out wrong. The idea behind a radiant barrier is to have mass coverage, not to create a seal. In fact, you NEVER want to create a sealed vapor barrier in your attic space in Florida, this is a big No No.

Also, going back to what coastal chic said, if people use closed cell foam to do a sealed attic in the southern humid states they may be setting themselves up for some possible rot and or mold issues. I'm and Architect and we have seen this before, so anyone reading this, please used an open cell foam, not closed cell. If conditions persist to where the dew point is reached in a wall or ceiling system, inside of the spray foam, water droplets can form in between the closed cells and essentially make the foam have no R-value and eventually de-laminate from the roof sheathing (due to the water weight). We have seen this at the microscopic level in a few different court cases, so don't make that same mistake. Many Spray foam manufactures insist that this wont happen, but again we have seen multiple court cases where this HAS happened.

[loves2read]

the problem comes I think to certain extent because people are transferring what they know about one area to another and expect that one size fits all thinking will work...

[d4g4m]

If your house was built decades ago with an on site stick built roof, you might be able to have a radiant barrier installed. If your house is newer with an engineered truss system that was delivered by truck and installed with a crane, there is no way a radiant barrier can be installed properly if at all.

[cupper3]

Originally Posted by d4g4m

If your house was built decades ago with an on site stick built roof, you might be able to have a radiant barrier installed. If your house is newer with an engineered truss system that was delivered by truck and installed with a crane, there is no way a radiant barrier can be installed properly if at all.

Why? It doesn't require to be sealed as adambeazley advised, so why could it not be installed on an engineered truss?

[gitnerdun]

Originally Posted by avb3

Why? It doesn't require to be sealed as adambeazley advised, so why could it not be installed on an engineered truss?

Sounds like a lot of labor to install. Time in a hot attic crawling out to the eaves with tools & material=$$$$.

[d4g4m]

If you live in a house with an engineered truss roof, go up in the 'attic' and take a look. If a portion of the roof is 'cathedral', there is no way a barrier can be installed. If all you are going to do is install a barrier between rafters in the areas you can access, it is an absolute total waste of money. Spend your money on getting the ceiling insulation to a thickness of 12" [R39]
Newer block homes have a radiant barrier on the walls installed in full sheets over the 3/4" studs spaced 16" attached to the blocks for drywall installation. Some builders install 3/4" styrofoam panels between the studs as standard or option.