Replies

1. 
   Greg | Mar 11, 2009 03:22am | #1

   Eric:

    

   Try  http://www.gp.com/build/product.aspx?pid=1398

    

    

   The older I get, the better I was....
1. 
   EricP | Mar 11, 2009 03:34am | #2

   Thanks Greg,

   That's a similar product to techshield.  I need an underlayment for the shingles themselves - something in place of felt.  There are lots of synthetic underlayments for roofs and lots of radiant barriers that apply inside the attic.  It seems like someone would combine the two!!

   I know Certainteed just came out with a "reflective" shingle but it does not seem to be available in the southeast.

   Eric

    

   Edited 3/10/2009 9:09 pm ET by EricP

1. 
   Greg | Mar 11, 2009 03:57am | #3

   Duh... been a long day and I can't read....

    

   Wish I could help you. For the life of me I can't understand why anyone in the southeast would want a dark roof, but here they love black shingles....

    

   I've been thinking about putting the reflective stuff (yes, that's the technical name of it) in my own attic to lower the temps up there. Can't hurt with the cooling load.The older I get, the better I was....

1. 
   Hazlett | Mar 11, 2009 02:06pm | #4

   black roof doesn't show algae as much---and even the algae resistant shingles now on the market have a limmited effectiveness--- but black is always black.
   stephen

2. 
   k1c | Mar 11, 2009 02:25pm | #5

   I think you are thinking of things like radiant heat shield such as sheeting for roof that has foil on one side. This type, however, needs an air space between the foil and the space that it is trying to shield. If the foil is touching something, such as rafter or insulation, the foil becomes a conduit of heat than shield, at least that is what I read somewhere. If you plan to put something between the face of roof sheeting and the roofing, such shield will not do any good by above logic. It would also shorten the life of roofing if it reflects the heat back to the roofing which would undercut any savings from insulating value. Hope this helps.

3. 
   andy_engel | Mar 11, 2009 02:42pm | #6

   I wrote a review of GP's product in FHB a few years back. That works not by reflecting heat, but rather by not radiating it. We all recognize that color affects how a surface absorbs heat, but most of us don't understand that color also affects how a surface emits, or radiates, heat. In short, dark colored surfaces tend to be good emitters - that's why most wood stoves are black. Light colors tend to be poor emitters. So, the radiant barrier sheathing has its shiny side facing down. The roof gets hot, but radiates much less heat inward. And yes, those places where the shiny surface touches another surface are compromised.

   Andy

   "Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein (or maybe Mark Twain)

   "Get off your dead #### and on your dying feet." Mom

   "Everything not forbidden is compulsory." T.H. White, The Once and Future King

4. 
   Matt | Mar 11, 2009 02:59pm | #7

   K1c's above post made me curious.  I too had read about the need for an air gap below the radiant barrier although I can't remember where I read it - it was years ago.

   Some quick Google searches turned up this article by supposed experts.  Of particular interest to you might be the section called "Can I just roll the material out on the roof before reshingling?" 

   If you really want to get superior knowledgeable read all this stuff.  I'm certain your customer will pay you more just based on your plethora of knowledge.  :-)  If you do read it let us know when you are going to hold the radiant barrier class. :-)

1. 
   EricP | Mar 12, 2009 04:08am | #8

   Matt,

   I'll knock out that reading this weekend and get back to you!  and Yes my customers do pay extra for my knowledge even if it comes from reading the night before!

   I talked to my two main shingle suppliers today and no one seems to have an underlayment but two manufacturers have shingles with radiant barrier properties.  I thought great! What's the price premium?  There was a pause on the phone and they said $180/square - almost 3 times my normal 30 yr shingle!

   Needless to say - no go there!  We are going to use a synthetic underlayment for the first time - maybe the light grey color will have some minimal effect at least during the install!

   Eric

1. 
   Matt | Mar 13, 2009 03:34pm | #9

   Yea - the thing with these energy upgrades (as with any material upgrade) you have to figure it in terms of value.  At an extra $115 or so a square it might take more then the life of the shingle to get the payback in energy savings.

   I'm sure your customer agrees and when you explain the thing about the airgap needed on a radiant barrier, they will understand that too.

   OTOH, that is what is so awesome about the radiant roof sheathing for new construction.  The entire upgrade might be in the $100 to $200 range so it's cheap and the payback is quick.