One great Myth of modern home construction is the "R-value" measurement used for
insulation. R-values have been peddled to consumers for so long they have taken on
"Chiseled-In-Stone" status. The saddest part of this myth is that the R-value by itself is almost a
worthless number, as it is impossible to define insulation effectiveness by this number alone.
So why is the R-value myth perpetuated? I don't know if anybody knows. It obviously favors
fiber insulations manufactured by Huge International Corporations, who regularly contribute to
political campaigns.
What would the R-value of insulation be after it has been submersed in water or had a 20 mile
per hour wind blowing through it? Obviously the "Effective" R-value of fiber insulation would go
to zero, but Spray Foam Insulation would be largely unaffected. Again, R-values are "funny"
numbers; they are meaningless unless we know the other important factors.
The use of R-values as the only criteria is absolutely ridiculous, yet we have Government
Agencies mandating R-values in the 20's, 30's and 40's today. Fiber insulation having an
R-25-value installed in a house, but not properly sealed will allow the wind to travel through it as
if there were no insulation at all.
R-values are a result testing the flow of heat through material in a sealed test fixture under
controlled laboratory conditions, but these conditions are not even remotely associated with the
real world installed performance of insulation. To calculate the actual installed performance of
insulation, we also need to know its resistance to air penetration, to internal air currents, to liquid
water, and to water vapor drive. What really matters is the "effective" R-value when insulation is
subjected to these real world conditions?
Fiber insulation is generally assigned an R-value of approximately 3.5 per inch, yet it can
only achieve this value when tested in an absolute zero air-movement and zero moisture
environments. Zero wind and zero moisture are not real-world conditions, as all homes leak air
and they sometimes leak water. In addition, water vapor from the atmosphere, showers,
cooking, breathing, etc. constantly moves back and forth through the walls and ceilings of our
homes.
If an attic is not properly ventilated on a fiber insulated home, the water vapor generated
inside a house will very quickly semi-saturate the insulation above the ceiling and in the walls.
Even small amounts of moisture will cause a dramatic drop, as much as 50 percent or more, in
fiber insulation's performance.
insulation. R-values have been peddled to consumers for so long they have taken on
"Chiseled-In-Stone" status. The saddest part of this myth is that the R-value by itself is almost a
worthless number, as it is impossible to define insulation effectiveness by this number alone.
So why is the R-value myth perpetuated? I don't know if anybody knows. It obviously favors
fiber insulations manufactured by Huge International Corporations, who regularly contribute to
political campaigns.
What would the R-value of insulation be after it has been submersed in water or had a 20 mile
per hour wind blowing through it? Obviously the "Effective" R-value of fiber insulation would go
to zero, but Spray Foam Insulation would be largely unaffected. Again, R-values are "funny"
numbers; they are meaningless unless we know the other important factors.
The use of R-values as the only criteria is absolutely ridiculous, yet we have Government
Agencies mandating R-values in the 20's, 30's and 40's today. Fiber insulation having an
R-25-value installed in a house, but not properly sealed will allow the wind to travel through it as
if there were no insulation at all.
R-values are a result testing the flow of heat through material in a sealed test fixture under
controlled laboratory conditions, but these conditions are not even remotely associated with the
real world installed performance of insulation. To calculate the actual installed performance of
insulation, we also need to know its resistance to air penetration, to internal air currents, to liquid
water, and to water vapor drive. What really matters is the "effective" R-value when insulation is
subjected to these real world conditions?
Fiber insulation is generally assigned an R-value of approximately 3.5 per inch, yet it can
only achieve this value when tested in an absolute zero air-movement and zero moisture
environments. Zero wind and zero moisture are not real-world conditions, as all homes leak air
and they sometimes leak water. In addition, water vapor from the atmosphere, showers,
cooking, breathing, etc. constantly moves back and forth through the walls and ceilings of our
homes.
If an attic is not properly ventilated on a fiber insulated home, the water vapor generated
inside a house will very quickly semi-saturate the insulation above the ceiling and in the walls.
Even small amounts of moisture will cause a dramatic drop, as much as 50 percent or more, in
fiber insulation's performance.
| The R-Value Myth |
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| Big Foam Insulators of Florida |
| "What's in your attic?" |
| Insulating the Planet Naturally |
| Call for free inspection: 352-239-5520 email: bg@bigfoaminsulators.com |