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I've
been getting conflicting information re radiant barriers. Are they useful in
cold climates (VT/NH). At the moment it seems as if it is not cost-effective.
Need
to have at air space (3 inches is most common recommendation) between
itself and warm air space wall/ceiling. Then pile on insulation. It is
difficult to retrofit a house with these specs, and not
cost-effective.
--
gilbert midonnet
No. I would agree with that thought
but those who are smarter than I, and there are many, say it faces the inside
of the attic. It may have to do with tear off. When you remove the old roofing
material it would also remove the foil. But then again the rolls of
radiant barrier are also applied to the underside of the sheathing not the top
regardless of the stage of construction. It is rolled out over the rafters in
new construction and stapled to the bottom of the rafters in existing
homes. I would think if it worked better on the top they would come up
with a tar paper that has foil applied so it would act as a barrier.But then
again it may be a cost item. I looked at rolls of radiant barrier in Home
Depot yesterday. $50.00 for 5'X125' roll, marked down from $75.00.
That would add a grand to a roofing job by the time you add material and
labor.
The ceramic paints that are applied to the metal roof do work better on
the outside than under the sheathing.
Applied to the outside, fifteen-thousandths of an inch of dried product,
in white, is equal to R-20, on the inside it is maybe R-5. Of course my
money is on the outside numbers dropping on a shady day.
----- Original Message -----
Sent: Thursday, January 03, 2002 11:59
AM
Subject: Re: [GBlist] tar-paper for
roofing
If you are trying to avoid the heat buildup
from the Texas sun, doesn't the radiant foil barrier have to be on the top
side?
Bob Jordan
----- Original Message -----
Sent: Thursday, January 03, 2002
12:23 PM
Subject: Re: [GBlist] tar-paper for
roofing
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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