Replies

1. 
   TRice | Jul 13, 2005 08:17pm | #1

   If the siding comes in contact with the foil, it is of no benefit. If there is an air gap adjacent to the foil side, it is an inexpensive means to increase the resistence of the material to outside-in heat gains. If the cost is more than 10% over the cost of non-reflective insulating board (rigid foam), it is a waste.

1. 
   wchips | Jul 16, 2005 12:42am | #2

         Hi Timbo

          How mutch air space would you recomend between the foil and the siding?

     A frind of mine put foil faced insolation board  about 10 years ago, he used vinal siding on his shop wich has some air space behind it, It made a big difference on hot days.

   I was thinking of residing my house using foil faced insulation under the siding, I was thinking og wsing fiber cement siding. and adding furring strips between the foil and the siding, say about 3/8'' or 1/2'' thick .to get a air space.

                         Have a nice day Lee

1. 
   Piffin | Jul 16, 2005 07:23am | #3

   The biggest advantage there is the foam has resistance to thermal transfer. After that, the great value is that the space will act asa drainage plain to help assure longevtiy of siding and pant.Finally, there would be modest value in the foil reflecting heat to the exterior. 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

2. 
   TRice | Jul 18, 2005 04:32pm | #4

   I know what is standard practice in the details of wall construction and how walls have been built that utilize an air gap (though no reflective surface) for a long time, but, to answer your question directly: I don't know. I believe that any gap will work. The heat transfer, without any direct contact between elements, will be affected by the character of the surface. In other words, this is when the reflective surface works.

   There is a great deal of data available on the insulating value of air gaps in walls for various conditions, orientations and differential temperatures, but you don't need a science project, do you?

   So any air gap should work fine.

1. 
   wchips | Jul 18, 2005 05:38pm | #5

   Thanks for the info guyes . I havent made up my mind yet as how i am going to proceed with this project.

                                 Have a nice day Lee

3. 
   paul42 | Jul 18, 2005 06:12pm | #6

   Most claims that I have seen have stated that 1/2" is adequate.

   Thin furring strips will be more likely to split when putting them up or nailing the siding to them.

   I used to like the idea of using treated lumber for the furring strips.  I used to use 2x stock and rip the thickness I wanted with the table saw.  With the new treatment they are using now, I'm not as certain that is a good answer.  Maybe somebody else on this forum can come up with a good answer there.

   The foil backing does make for a decent drainage plane behind the siding.  I like the idea of taping all of the joints in the foil with foil tape.  Might only make sense for the DIY projects though.

1. 
   wchips | Jul 19, 2005 04:48pm | #7

     I was thinking of using 3/8'' or1/2'' cdx ply for furring strips , ripping say1 1/2'' strips, and placing directley over the exsisting studs. I would use nails long enough to go through the siding , furring strip, foam board , ect . The nails would have to be approx. 3'' long.

                                                Have a nice day Lee.

1. 
   paul42 | Jul 19, 2005 07:37pm | #8

   The siding is there to protect everything underneath from the sun and physical damage.  It stops most but not all of the water.  I'm paranoid and wouldn't trust the CDX plywood without some sort of water protection.  There is a reason that they put the tar paper or house wrap over the OSB or plywood sheathing on a house.