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When the sheathing is applied to the roof the shiny side faces down. The
difference in price between standard sheathing and the sheathing with the foil
already applied is only around five dollars per 4X8 sheet. It may be slightly
more temperature efficient to apply a radiant barrier on the underside of the
rafters when new but after a short time it is coated by dust and would not be
advantageous. The labor cost on the other hand would cause people to just leave
it out of construction all together.
The temperature difference in an attic here in South Texas utilizing this
type of product vs. one that does not is amazing.
The greatest amount of heat gain is through the roof making this product
cost and actually effective, reduces the demand for electricity, and
most important, saleable to people building a home that would not consider green
building products. Until a green building product is in use, it isn't actually a
green building product.
So the answer to the question is, no, it still works. Although it would
work better with one, if you can keep the radiant barrier clean.
Doesn't there need to be an air space between the
radiant barrier and the tar paper for the radiant barrier to
work?
Bob Jordan
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