R-Values and Radiant Barriers
Most people are familiar with the term R-Value when discussing
insulation properties. An R-Value is a measure of how long it takes a
heat "absorbing" product to absorb 100% of its potential and begin to transfer
the heat out the other side of the product. R-Values are calculated via a controlled
test under the following conditions:
Isn't it odd that products designed to protect us from the
heat are rated using a test that is performed under 75 degrees Fahrenheit with
50% humidity? An interesting fact is that as the temperature rises, the
R-Value of an insulation material decreases.
Therefore, R-Values themselves don't mean much unless they
are used to compare different products with R-Values. Basically, a product
with a higher R-Value is better than a product with a lower R-Value. A
higher R-Value product takes longer to absorb 100% of it's potential and therefore,
is more effective at "delaying" the transfer of heat.
But R-Value is a misleading number when it comes to talking
about reflective foil insulation. R-Value only measures
CONDUCTIVE HEAT (heat
transferred by physical contact) but 90% of all summer heat gain and 75% of
all winter heat loss is caused by
RADIANT HEAT (heat
transferred from a heat source and move through the air).
Radiant barriers do not "absorb" heat. Instead, they
reflect up to 97% of the heat that hits it and therefore, have no R-value rating.
Installing a radiant barrier between the heat source (sun)
and an existing R-Value rated insulation will improve the effectiveness of the
R-Value rated insulation. Why? Because only 3% of the heat is now
hitting the R-Value rated insulation and therefore, it will take longer for
it to absorb 100% of it's potential thereby holding the heat longer before passing
out the back side into living spaces.
In summary, you increase the R-Value
of your existing insulation by installing a radiant barrier foil insulation
product. Studies have found the following about radiant barriers to be
true:
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The Tennessee Value Authority studies state that
radiant barriers combined with an R-11 insulation has the same affect
as an R-19 insulation alone. Add a radiant barrier to an R-19
insulation and you have the effect of an R-30 insulation alone.
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The Florida Solar Energy Center specialist Philip
Fairey found that a radiant barrier combined with an R-19 insulation
produced a LOWER annual energy consumption than an R-30 insulation alone.
R-Values and Radiant Barriers
You can however achieve R-Value ratings by using radiant
barrier bubble insulation
products in a variety of installation manners. Please see "The
Many Uses of Radiant Barrier Insulation" page on our website.