On Apr 9, 7:24*am, Eric in North TX wrote:
I keep running into to people planning on installing this coating the
inside of their attic roof. I tend to roll my eyes, but maybe somebody
could enlighten me. 1st; how could it work when the light/heat is
already having to pass through roughly an inch of tar and wood. 2nd:
even if it did work, what possible difference could it make. Reducing
the heat load in an attic ( assuming this works, which is quite an
assumption) doesn't seem like the best bang for the buck for reducing
your hvac costs.

Maybe www.energystar.gov has info or links.

On Apr 9, 11:20*am, ransley wrote:
On Apr 9, 7:24*am, Eric in North TX wrote:

I keep running into to people planning on installing this coating the
inside of their attic roof. I tend to roll my eyes, but maybe somebody
could enlighten me. 1st; how could it work when the light/heat is
already having to pass through roughly an inch of tar and wood.

It works by stopping the radiant heat from continuing on into the
attic and warming it up more. Ever sit under one of those radiant
heaters that are used on patios during cool weather? The radiant
heat warms you. Imagine putting a thin radiant blocking barrier
between the heat source and you. You would no longer be warmed by it.

If its stapled to the rafters, which is where it's usually deployed,
there is air flow from soffits up to a ridge vent, taking the heat
between the barrier and the roof out.







2nd:
even if it did work, what possible difference could it make. Reducing
the heat load in an attic ( assuming this works, which is quite an
assumption) doesn't seem like the best bang for the buck for reducing
your hvac costs.


Depends on the climate, existing insulation, is the SC unit in the
attic, etc. I've seen data that show in hot climates it does make a
significant difference. As for the bang for the buck, it's very
cheap to install. You can do an attic yourself for $250 or so.



Maybewww.energystar.gov*has info or links.

That would be a good place to start.

It works by stopping the radiant heat from continuing on into the
attic and warming it up more. Ever sit under one of those radiant
heaters that are used on patios during cool weather? The radiant
heat warms you. Imagine putting a thin radiant blocking barrier
between the heat source and you. You would no longer be warmed by it.

If its stapled to the rafters, which is where it's usually deployed,
there is air flow from soffits up to a ridge vent, taking the heat
between the barrier and the roof out.





Operative word is air flow, do not lap courses, 1/8" space between, do not
close off any rafter cavities.