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Posted by buffalobill on October 9, 2006, 7:11 am
"A radiant barrier reflects radiant heat energy instead of trying to
absorb it. What does this mean in your home or business? During the
winter, 50-75% of heat loss through the ceiling/roofing system and
65-80% of heat loss through walls is radiant. In the summer, up to 93%
of heat gain is radiant. If you are depending on R-value (resistance)
alone to insulate against heat gain and loss, remember that thin layers
of fiberglass are virtually transparent to radiant energy and are
affected by changes in humidity (moisture levels). A 1-1/2% change in
the moisture content of fiberglass insulation will result in a 36%
decrease in performance (referenced from HVAC Manual 10.6;
McGraw-Hill). A pure aluminum radiant barrier is unaffected by humidity
and will continue to perform at a consistent level no matter how humid
it may be."
more at:
http://www.radiantbarrier.com/what_is_radiant_barrier.htm
where is the barrier?
The Quintessential Man... wrote:
> I have a problem concerning my radiant attic barrier that I don't have
> the background to resolve.
>
> At the start of the summer I had a radiant barrier coating (e.24, 76%
> efficient) installed in my house attic. I already had mechanical
> ventilation (although not enough) and was forestalling the installation
> of more ventilation until I got the numbers back on the performance of
> the radiant barrier (radiance brand by Degausa.) I have an attic of
> similar construction and orientation over my detached garage that has no
> barrier and little if any ventilation. I installed thermistor
> temperature sensors connected to a data logger in both attics at similar
> locations and log the temperature 24/7. The temperature curves, with
> respect to time, curves are virtually identical. The exception is that
> the barrier attic seems to heat up a little faster until the fan comes
> on at which point the two curves line up; it is as though it is trapping
> heat. Even if the issue is lack of ventilation, as the contractor
> contends, should I not still expect to see a lag in the temperature rise
> over time in the treated attic as opposed to the untreated attic. I
> have also taken interior surface (underside of decking) readings with an
> infrared sensor (Fluke 61) and detect no noticeable difference.
>
> Either I am measuring this wrong or the barrier is not working. The
> contractor's expertise seems to be more on the area of installation and
> less in troubleshooting. They seem convinced that I need more
> ventilation, but if that is the case of what value is the radiant
> barrier, I would just merely add a bigger fan... The only real
> advantage I can detect from the barrier so far, is that one lone light
> bulb really brightens up the attic now...!
>
> Please help
>
> Thanks
> John
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