I think it would make a difference, but I'm not in construction.

The radiant barrier pushes hot air up and out of roof vents or ridge vents. Does your patio have ridge vents?

Isn't it attached to the decking in this case?

I'm somewhat in the same boat, but I'm getting a new roof due to hail.

Since it isn't cost effective to rip off the old decking, I'm using a product called polaralum that is used as an underlayment under the shingles.

It might be cheaper to look at something like that, but the techshield is probably better.

All the new construction I see these days has the radiant barrier decking.

The cost to go with the polaralum (since I'm already having to get new shingles) is about half of what it would cost to put in a radiant barrier in the attic.

I hope it works.

Radiant barrier doesn't push hot air. It reflects radiant heat. Radiant barrier is independent of any convection systems ala ridge vents etc.

Also for any radiant barrier to work the under side must be next to air. So if you're in your attic you need to be looking up and can see it. That's why they put it on the under side of decking. You can't put it between decking and shingles.

Yes it makes sense. By lowering the attic temp above the porch will allow less heat to transfer through the porch ceiling material. Even if this is not significant it is worth it for lowering the heat in the attic which will allow the shingles to last longer. If the whole house is done it will drop temps on average 15-20 degrees in the attic if there is adequate soffit and ridge venting.

FYI - Once again, radiant and convection heat transfer are independent of each other. As a home owner you want to improve radiant, convection, and conduction = insulation.

If they are installing it on the house, 99.9% of the time they will install it on the patios as well. Doesn't make sense to try and piece in a different product over such a small area as there would be little to no true cost savings.

If it is a free standing open air structure away from the home, the radiant barrier will probably have very little/if any noticeable difference but again the cost between the two products is very minimal on that type of job.

[This message has been edited by DaybreakAg (edited 2/28/2014 6:48a).]