reflective insulation

 does the reflective insulation (mylar/ metalized) need an air gap to
reflect heat back?
thanks
gary

 

Take a look at http://www.reflectixinc.com/diy/default.asp?pageIndexT7  for
some information on how to use one of the more popular radiant barrier
products in a large number of different applications. This is everything
from installing it for your water heater or the wine room, to the crawl
space or attic.

 greif wrote:

Heat (energy) travels via radiation, conduction and convection.
Reflective foils only block radiation and don't do anything to
stop conduction and convection. An air gap stops conduction and,
if it's a small gap, it'll reduce convection as well.

Anthony

 Yes, Tests show that reflective insulation under concrete accomplish
absolutely nothing.

 

Yes.  It works by stopping radiation (one of the three methods of heat
transfer).  But in many cases you get more insulation effect by adding as
little as 1/4 of foam.

It *does* have some application in high temperature environments.

It is also best to install it such that it won't get covered with dust (in
attics, it's recommended to cover the rafters so it is facing downward).  If
it gets much dirt on it, it loses its low reflectivity (dirt on the surface
will rase the emissivity).

daestrom