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Mylar versus Aluminum Radiant Barriers

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Posted by D on August 12, 2003, 11:21 pm
I'm thinking of insulating an RV for travel to the Southwest and later
Canada.  I'll be in the Southwest desert during the end of summer and
Canada during the late Fall/Winter (Why not wait until the weather
gets cooler or warmer?  I'm doing nature photography).  The RV is
small and very poorly insulated.  I removed the sytyrofoam insulation
(what little there was), and am thinking of putting in
a radiant barrier to keep unwanted heat out and in desired heat.
While I can use the air conditioning to cool in the interior, I don't
want to run the engine all the time to keep the battery charged, and
the solar panel I'm installing has its limits as well.

In addition to a radiant barrier, I'm also putting in window barriers,
fiberglass insulation, and a vent fan.

Does anyone have any thoughts about the use of Mylar (as in the space
They work great at keeping heat in, but are they useful as a radiant
I'm told they are flammable whereas aluminum foil barriers are not.
Any thoughts on this?  I've heard of aircraft crashing after its mylar
blankets caught fire.

And why should radiant barriers be installed with the shiny side in or
down? I thought the shiny side should face outward or upward against
the sun.  Any thoughts on this?

Thanks in advance.

Posted by albown on August 13, 2003, 3:14 pm

Check out the rigid poly styrene at the local building supply. You need
inches or mass to stop the heat or cold transmission. You might consider
taking your unit to a insulating contractor and having it sprayed with foam.
That would probably be the best.  I live in Arizona and if your coming to
the central deserts I would suggest you get a quiet gen to run the a/c at
night. This morning it was a balmy 92 F when I got up at 6:30. I live in the
Phoenix area. Higher elevations will be much cooler.

Posted by Roland Burton on August 13, 2003, 5:04 pm
 I think that Mylar works with radiative heating only, like direct sunlight,
and it's good if that's what you have to insulate against.  But if you have
to deal with conduction and convection, like through the wall of an
uninsulated trailer in a cold place, you need something with real insulation
in it, like foam or glass wool.  I don't see many refrigerators with mylar
insulation, and those guys probably know what they are doing.

Posted by Fred B. McGalliard on August 13, 2003, 7:28 pm
 Mirror coated Mylar prevents you from radiating heat just as it prevents
radiant heat from being absorbed.



Posted by Brent Geery on August 14, 2003, 6:39 pm
 On 12 Aug 2003 16:21:25 -0700, dkroman@uclink.berkeley.edu (D) wrote:

Rethink using fiberglass insulation.  They have much better (foam)
insulation technologies.  Even using the best technologies, you will
be severely under insulated by building standards.

BRENT - The Usenet typo king. :)

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