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Single-sided
foil (one foil side) with another material backing such as kraft paper
or polypropylene. Some products are further strengthened by fiber
webbing sandwiched between foil and backing. The strength of the
backing material is important since unreinforced foil tears very
easily.
Foil-faced
roof sheathing materials that come from the manufacturer with a foil
facing adheared to one side of the sheathing.
Double-sided
foil with reinforcement between the foil layers. Reinforcement may be
cardboard, kraft paper, mylar or fiber webbing.
Foil-faced
insulation. The insulating material may be polyisocyanurate,
polyethelene "air-bubble" packing or other materials that
impede heat conduction.
Multilayered
foil systems. When fully extended and installed so that the foil
layers do not touch, these products also form insulating airspaces.
Radiant
barrier "chips" are also manufactured and sold. This product
is slightly different than a conventional sheet-type radiant barrier
in that the "chips", which are blown onto the floor of the
attic — typically to a depth of 3 or more inches, act as a
multi-layer product with many "traped" air pockets. These
air pockets cause this product to function somewhat like traditional,
fibrous insulation products. Even though this product may collect dust
on its uppermost layer, the remaining layers and air spaces work to
significantly reduce heat transfer through the ceiling assembly.
Some of
these products may have R-values, which may be claimed only if the product
was tested according to Federal Trade Commission regulations for
insulation.
Although it is not by definition a radiant barrier, there is a low-emissivity
paint available that can be applied directly to the underside of the roof
decking. |
Saturday July 05, 2008 - 12:44 PM
