Comments on: New Video=> Let Me Show You Why Radiant Barrier Under Shingles Just Won’t Work

By: Ed Fritz

Ed Fritz — Wed, 15 Sep 2010 04:17:11 +0000

Bob, It would be tricky to get an air space and radiant barrier below a foam roof. Since the roof is flat, I would consider adding a couple of inches of ISO board and then going over with single ply “Cool” membrane roof like http://www.Duro-Last.com

This is an awesome roof for flat/commercial roofs. The roof has a high reflectivity and low emissivity. It acts like a radiant barrier by not absorbing much heat. You can walk around barefoot on a 100 degree day on these roofs.

By: Bob

Bob — Mon, 06 Sep 2010 17:00:26 +0000

I live in Phoenix, AZ, have a flat roof that needs to be replaced.
Can I use a radiant barrier under a built up foam roof If I can figure out a way to provide an air space. I’m thinking of barrier, furring strip, plywood, foam.
Will that work?

By: Ed Fritz

Ed Fritz — Wed, 09 Jun 2010 21:24:53 +0000

Gabriel,

Respectfully, there is no “air pocket”. My point is that physics is physics. Radiant heat by definition can ONLY travel across and air space (void, nothingness). Without an air space you cannot have radiant heat since you have a “solid”. If you look at their own information it says an air space is required to act as a radiant barrier. So, I am in agreement with the manufacturer. As for the energy saving – I’d agree with you – “…there’s something else at work” but it’s not the underlayment doing it.

By: Gabriel

Gabriel — Wed, 02 Jun 2010 17:11:52 +0000

Well, in my area in Texas, the xxxxx is pretty much the only one available in the area except by Special Order and the only one i have personal experience with, and so, its the only one i can personally vouch for. I’m one of the principals at a construction company and I did my homework before recommending it to our clients. The data seemed solid, it had its government certifications, and we went with it. Every One of our clients love it and are ecstatic we recommended it and are experiencing an average of about 40% reductions in utility bills. One client went from $1200 a month last April to $242 this April. So, while your theory sounds good, apparently that little white layer gives enough of an air pocket to do the job or there’s something else at work here, because it has definitely made a huge difference in each and every installation.

By: Ed Fritz

Ed Fritz — Wed, 28 Apr 2010 16:01:06 +0000

Shane, This still won't work. There is an air space INSIDE each layer of cardboard, but there is NO airspace BETWEEN the layers of cardboard where the layer of foil is installed. The foil has full and direct contact with the cardboard on the inside layers. The ONLY layers of foil that are effective as a radiant barrier in this product are the two outer layers. However, the minute you lay the product on something flat you eliminate the effect of the bottom layer and then if you lay something on top like shingles you eliminate the radiant barrier on top. The net result is you end up with a multi-layer of cardboard between the shingles and the roof deck. This will help some to reduce conductive heat flow through the roof assembly. Or, you could just install some cardboard or a thin layer of foam board to get the same result. It sounds like your "rafter room" is a cathedral ceiling. If your only access is from the outside (roof side), I would recommend installing ISO board (Polyisocyanurate Board) between the shingles and the roof. This is basically how commercial roofs are built. If possible, I would look to doing a ventilated skin roof with either tile, or metal so you can install a radiant barrier and still have the required air space.

By: Shane

Shane — Wed, 28 Apr 2010 01:19:07 +0000

Have you tried out the Truprotect product. It seems like it would be an effective radiant barrier that you can apply directly to your roof because the corrugated board provides the air space. Foil, board, foil, board, foil, all laminated together.

I have to redo an addition to our home that is a “rafter room,” and it is an oven in the summer. I have to find some way to insulate from the roof side. I’m thinking truprotect would be a good option…yes? no?

By: jeff

jeff — Thu, 25 Mar 2010 14:55:59 +0000

The funny thing about this is I told a guy that I was trying to sell a roof to that it would not work but my competition said it would. He used them instead of me. I told him to use techshield. Hope he gets any of his money back in savings on his electric bill. LOL.

By: Jason

Jason — Sat, 20 Mar 2010 23:57:07 +0000

Thanks. Have to say the 2nd video really helped my understanding of your reply. Glad you included it, not sure I’d have gotten it otherwise.

By: Ed Fritz

Ed Fritz — Sat, 20 Mar 2010 19:33:21 +0000

Techshield is a good product and I recommend it for new construction. The required airspace is actually the attic itself. Techshield or any other product applied DIRECTLY to the bottom of the roof deck is actually working off the LOW EMISSIVITY quality of the aluminum foil rather than the reflectivity quality. This is similar to wrapping a hot potato with foil to keep it hot. In general, if the air space is on the "hot" side of the radiant barrier it is working off of reflectivity. If the air space is on the "cold" side of the radiant barrier it is working off the emissivity quality. Here is a video on why an air space is required.

By: Jason

Jason — Sat, 20 Mar 2010 18:43:00 +0000

So… What’s your take on LP Techshield? By most all accounts it works, but it’s attached to the decking? Forgive me if this is a stupid question but it seems to me that there’s no air gap between the foil and the roof deck in that scenario either?