I would be very interested in knowing the effectiveness of heat reflective paint on the interior of an exterior wall. Hytech has a reflective primer barrier to use under conventional top coat, but I am unsure how the top coat/primer interface will effect the IR reflectance. Will it maintain high reflectance without an air intereface? Also, the Hytech paint uses Aluminum particles, so there goes my cell phone reception! Any alternatives?

I'm a scientist experienced in spectroscopy. This is
the study of light in conjunction with materials.

One of the best reflectors is magnesium oxide. When a test
instrument is used it's magnesium oxide which is used to
reflect light.

Nearly any materials absorb after you get past the red color
into infrared and only things like gold or well polished
aluminum will reflect heat without absorbing heat itself.

It's hard to make a good heat reflector from even a polished
sheet.

I don't know any specs for paint but from my experience I
believe you will find that bright white paint is the best
for all round use for even reflecting heat.

Otherwise consider using a new material which is simply
aluminum deposited on a plastic base. It's unique because
for $2.00 / sq foot it can withstand 10+ years of direct
sun with only clean water rinsing.

If you're interested in the product that I know of reply
and I'll go looking for it.

Regards,
Andre

As I know, this type of additive (painted on the sun exposed roof and walls) are effective against overheating... of course until the surfaces are clean. It doesn't replaces the heat insulation in winter.

I believe in proper attic and roof ventilation that sucks the warm air out in summer, and a good heat insulation for the whole year.

Insulatingâ Paint Merchants Dupe Gullible Homeowners
As Con Artists Profit From âÂÂInsulatingâ Paint, the FTC is MIA

http://www.greenbuildingadvisor.com/blogs/dept/musings/insulating-paint-merchants-dupe-gullible-homeowners

I would love to roll on an extra R38 of insulation in a light tan semi-gloss. I know such a product is available but I haven't much time to research lately. I found a bridge for sale in Arizona on Craigslist and have been occupied with that also.