Radiant barrier foil

opiesche · 01-02-14, 05:24 PM

A few months ago, I finally took the step to install some radiant barrier in my attic. Here in NorCal, summers go well above 95 degrees outside for a period of 2 months or so, with the sun beating down all day long, and the house gets incredibly hot - especially the second floor, of course (there's no AC). After stapling radiant barrier to the inside of the trusses only on the south facing side of the roof, max interior temperature on hot days is down as much as 8 degrees. The roll cost 100 bucks. If I had central AC, the barrier would probably have paid for itself in the first summer. As it stands, temperatures are much more comfortable with it. Anyone having heat problems, I can highly recommend this stuff!

AC_Hacker · 01-02-14, 08:25 PM

Quote:

Originally Posted by opiesche

A few months ago, I finally took the step to install some radiant barrier in my attic...

Did you use the Foil covered bubbles?

-AC

opiesche · 01-04-14, 04:48 PM

No, just a thin reflective foil. Looks like it's two layers of Polyethylene with vapor deposited aluminum between. It doesn't insulate by itself, just reflects IR back from the underside of the roof.

opiesche · 01-04-14, 04:49 PM

This stuff:
Reflectix 4 ft. x 125 ft. Heavy Duty 50 g Perforated Radiant Barrier-RB4812550 at The Home Depot

Student 07 · 01-10-14, 09:06 PM

I have a couple questions for you. What style of roof do you have, Gambrel, hip roof, Mansard? A picture would be great. How is your attic vented? Were you concerned about wind knocking the barrier down?

ecomodded · 01-11-14, 12:11 AM

Could this product work in cold Climates to redirect heat back into the house ?

I wonder if it would conserve energy/heat if you were to use it foil side facing in on a inside ceiling to reflect radiant heat back into the house on a cold winters day..

or would using it foil side up on the inside ceiling be better in such a application ?

Exeric · 01-11-14, 03:37 PM

Quote:

Originally Posted by ecomodded

Could this product work in cold Climates to redirect heat back into the house ?

I wonder if it would conserve energy/heat if you were to use it foil side facing in on a inside ceiling to reflect radiant heat back into the house on a cold winters day..

or would using it foil side up on the inside ceiling be better in such a application ?

I think your idea should work. The problem is that it is generally recommended that at least 12" or so of insulation be on top of the ceiling to conserve heat. This is because this is the most effective way to trap the heat below and keep out cold. This is far more effective than a radiant barrier but far more costly. If you don't presently have insulation above the ceiling I would think you'd be freezing living in Vancouver. If you do have insulation then a radiant barrier would be an inconsequential addition to it. Also, there is the problem of the air space you would need between the barrier and the ceiling...

ecomodded · 01-11-14, 05:07 PM

In a fully insulated house. If it was installed under the drywall foil side facing in to act as a radiant barrier to keep heat in it, for new construction or a extensive reno.
Seems to me they have foil faced fiberglass insulation not sure what side they face up..

ecomodded · 01-12-14, 04:41 PM

I found this on a Gov. website

Most common insulation materials work by slowing conductive heat flow and -- to a lesser extent -- convective heat flow. Radiant barriers and reflective insulation systems work by reducing radiant heat gain. To be effective, the reflective surface must face an air space. Dust accumulation on the reflective surface will reduce its reflective capability. The radiant barrier should be installed in a manner to minimize dust accumulation on the reflective surface.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
it would need to be glued to the ceiling reflective side facing in.

Radiation losses

Radiation losses can be reduced by using special plasterboard that is backed with a sheet of aluminum foil. The shiny metal foil acts as reflector of infrared radiation. Some of the infrared radiation is reflected back into the room and heat losses by radiation are therefore reduced. Metal foil placed behind a radiator that is fixed to an outside wall also helps to reduce heat losses by radiation.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

So you can stop radiation losses.

iamgeo · 01-12-14, 05:12 PM

Well, the foil faces the living space. I have the the roof decking that has the foil on the underside of it. Called Techshield.LP Building Products | LP TechShield Radiant Barrier
I can vouch for using just plain old Standard weight Aluminum foil as a way to keep the heat in the house.
[IMG]

[/IMG]
Read more here starting at post #14.................
http://ecorenovator.org/forum/applia....html#post9662

If I were going to retrofit foil in my attic I would use this something way less expensive than the product at Lowes or Home Depot...........
FOIL ROLL 18"X1000' ROLL STANDARD WEIGHT FOIL - Dean Supply

01-11-14, 12:11 AM	#6
ecomodded Supreme EcoRenovator Join Date: Sep 2012 Location: Vancouver Island,Canada. Posts: 1,037 Thanks: 116 Thanked 100 Times in 87 Posts	Could this product work in cold Climates to redirect heat back into the house ? I wonder if it would conserve energy/heat if you were to use it foil side facing in on a inside ceiling to reflect radiant heat back into the house on a cold winters day.. or would using it foil side up on the inside ceiling be better in such a application ? Last edited by ecomodded; 01-11-14 at 12:19 AM..

01-12-14, 05:12 PM	#10
iamgeo Apprentice EcoRenovator Join Date: Aug 2010 Location: Lakehills, Tx Posts: 168 Thanks: 4 Thanked 10 Times in 9 Posts	Well, the foil faces the living space. I have the the roof decking that has the foil on the underside of it. Called Techshield.LP Building Products \| LP TechShield Radiant Barrier I can vouch for using just plain old Standard weight Aluminum foil as a way to keep the heat in the house. [IMG][/IMG] Read more here starting at post #14................. http://ecorenovator.org/forum/applia....html#post9662 If I were going to retrofit foil in my attic I would use this something way less expensive than the product at Lowes or Home Depot........... FOIL ROLL 18"X1000' ROLL STANDARD WEIGHT FOIL - Dean Supply

01-02-14, 05:24 PM	#1
opiesche Helper EcoRenovator Join Date: Jul 2012 Location: Rohnert Park, CA Posts: 99 Thanks: 4 Thanked 14 Times in 9 Posts	Radiant barrier foil A few months ago, I finally took the step to install some radiant barrier in my attic. Here in NorCal, summers go well above 95 degrees outside for a period of 2 months or so, with the sun beating down all day long, and the house gets incredibly hot - especially the second floor, of course (there's no AC). After stapling radiant barrier to the inside of the trusses only on the south facing side of the roof, max interior temperature on hot days is down as much as 8 degrees. The roll cost 100 bucks. If I had central AC, the barrier would probably have paid for itself in the first summer. As it stands, temperatures are much more comfortable with it. Anyone having heat problems, I can highly recommend this stuff!

01-04-14, 04:48 PM	#3
opiesche Helper EcoRenovator Join Date: Jul 2012 Location: Rohnert Park, CA Posts: 99 Thanks: 4 Thanked 14 Times in 9 Posts	No, just a thin reflective foil. Looks like it's two layers of Polyethylene with vapor deposited aluminum between. It doesn't insulate by itself, just reflects IR back from the underside of the roof.

01-04-14, 04:49 PM	#4
opiesche Helper EcoRenovator Join Date: Jul 2012 Location: Rohnert Park, CA Posts: 99 Thanks: 4 Thanked 14 Times in 9 Posts	This stuff: Reflectix 4 ft. x 125 ft. Heavy Duty 50 g Perforated Radiant Barrier-RB4812550 at The Home Depot

01-10-14, 09:06 PM	#5
Student 07 Helper EcoRenovator Join Date: Dec 2011 Location: Gresham OR Posts: 35 Thanks: 0 Thanked 3 Times in 3 Posts	I have a couple questions for you. What style of roof do you have, Gambrel, hip roof, Mansard? A picture would be great. How is your attic vented? Were you concerned about wind knocking the barrier down?

01-11-14, 05:07 PM	#8
ecomodded Supreme EcoRenovator Join Date: Sep 2012 Location: Vancouver Island,Canada. Posts: 1,037 Thanks: 116 Thanked 100 Times in 87 Posts	In a fully insulated house. If it was installed under the drywall foil side facing in to act as a radiant barrier to keep heat in it, for new construction or a extensive reno. Seems to me they have foil faced fiberglass insulation not sure what side they face up..

01-12-14, 04:41 PM	#9
ecomodded Supreme EcoRenovator Join Date: Sep 2012 Location: Vancouver Island,Canada. Posts: 1,037 Thanks: 116 Thanked 100 Times in 87 Posts	I found this on a Gov. website Most common insulation materials work by slowing conductive heat flow and -- to a lesser extent -- convective heat flow. Radiant barriers and reflective insulation systems work by reducing radiant heat gain. To be effective, the reflective surface must face an air space. Dust accumulation on the reflective surface will reduce its reflective capability. The radiant barrier should be installed in a manner to minimize dust accumulation on the reflective surface. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ it would need to be glued to the ceiling reflective side facing in. Radiation losses Radiation losses can be reduced by using special plasterboard that is backed with a sheet of aluminum foil. The shiny metal foil acts as reflector of infrared radiation. Some of the infrared radiation is reflected back into the room and heat losses by radiation are therefore reduced. Metal foil placed behind a radiator that is fixed to an outside wall also helps to reduce heat losses by radiation. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ So you can stop radiation losses.