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Default Radiant barrier delima

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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Default Radiant barrier delima

"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_i...nt_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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Default Radiant barrier delima

buffalobill wrote:

"... During the winter, 50-75% of heat loss through the ceiling/roofing
system and 65-80% of heat loss through walls is radiant.


No way :-) An R30 wall plus a radiant barrier might be R33 at best.

... 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."


No. With no moisture protection, it will oxidize and perform poorly.

Nick

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