Replies

1. 
   Danno | Jan 13, 2007 06:16pm | #1

   I think it's been discussed here--you could try using the "search" function.

   http://www.Buildingscience.com may talk about it too.

2. 
   hammer1 | Jan 13, 2007 06:29pm | #2

   From what I've read, reflective surfaces don't work once they are covered.

   Beat it to fit / Paint it to match

1. 
   user-261763 | Jan 13, 2007 06:57pm | #3

   Radiant barriers are intended to be installed on the underside of the roof rafters. The theory is that the radiant heat from the sun will be reflected back up before it enters the attic. This, of course is in a sunny area of the country. I am not sure if a radiant barrier would help keep heat inside a home in cold climates. I would think it would not be worth the expence.

1. 
   toledo | Jan 14, 2007 06:47am | #4

   thanks for your replies....

    

   let me get a little more explicit - I understand that a radiant barrier must have an air gap between it and the heat source or it will conduct the heat; but can that air gap be filled with fiberglass, or will that still conduct? FG doesn't seem like much of a heat conductor.....

1. 
   Matt | Jan 14, 2007 07:09am | #5

   Don't know but I thought that radiant barrier was supposed to go betweent he insulation and the exterior...  Ask someone in texas - it's popular down there.

   BTW - can't remember exactly what car siding is - I've read about it here, but it is not to my knowledge used in my part of the country, but if it is what I think it is, I think I'd want a good air barrier of some sort behind it.

1. 
   toledo | Jan 15, 2007 05:36pm | #6

   thanks for the repy - my internet was down so I'm just now back online...

   it does seem that the best place for a radiant barrier would be between roof deck and insulation, with air gap, but....

   then it must be perforated so as not to be a  vapor barrier in the wrong place; and carsiding is a tongue in groove 1x6, not a good vapor barrier, so, I'm going with 1/2 in. foil-foam board under it for an air seal as you mentioned.

   just wondering if the foil aspect would do any real good in that location...

   thanks again....

2. 
   atrident | Jan 15, 2007 08:30pm | #7

     I have seen perforated foil for sale on E-Bay. They also sell a foil housewrap. I think you are on the right track.

3. 
   toledo | Jan 15, 2007 09:45pm | #8

   yes, they sell perforated foil, but this is a hurry up scenario, and I was thinking that this foam board would add insulation, isolate the framing, seal the air gap - lots of good stuff...but then I remembered that foam board is supposed to be covered by a flame retardent such as sheetrock, so I'm back debating it.....

   the whole house is covered by 2 to 4 layers of wood, lots of it old, dry, and pitchy - a veritable tinderbox...so what's a little foam board gonna hurt....?

   somebody stop me......

4. 
   etherhuffer | Jan 16, 2007 01:38am | #9

   If heat buildup is the issue, why not a roof fan with a thermostat that comes on when it gets hot? The  heat has to go somewhere. I have always thought that reflecting heat back is ok but would generate higher temps on the other side. Reduced shingle life?Those who can make you believe in absurdities can make you commit atrocities- Voltaire

5. 
   toledo | Jan 16, 2007 06:25am | #10

   pardon my ignorance, but what does a roof fan ventilate? this is a 12/12 , 2x6 roof, attic room with dormers, knee walls, and only a 2ft flat - there are a few roof vents, so I guess that is where a roof fan would go...did I answer my own question...?

   thanks for the reply

6. 
   etherhuffer | Jan 16, 2007 07:49am | #11

   Well, I guess. Just thinking that even with minimal air behind the interior walls, flow might cool it down. An "attic" fan of low cfm might keep hot air from stagnating in the spaces, no?Those who can make you believe in absurdities can make you commit atrocities- Voltaire