Installing radiant barrier foil on a flat roof

Factual Questions
1

Getting a new roof installed… adding beams to make the roof 10" higher so I can have insulation installed (plans already approved by the city) and going to put a new top layer of plywood in with radiant barrier foil (currently don’t even have a top layer of plywood). And yes, our roof is completely flat and the new one will be as well (roof doesn’t leak at all, doing all this to make house more energy efficient).

Now, from what I understand, the foil needs about 1/2 space between it and the nearest insulation in order for the foil to do its job…

But is the foil side of the plywood supposed to face up (towards the sun, though it’ll obviously be covered up by the roof), or down, towards the house?

If down… we want to use cellulose insulation. But it’s hard to get that level to a point where the installers can ensure a uniform 1/2" of space (or anywhere near that) between the top layer of insulation and the plywood. If that’s the case, we may be forced into using rolled bats, which I’d rather avoid.

Anyone have experience with this? Advice? Suggestions? Tips? :confused:

2

Bump.

3

I have never used this product nor to be honest have I heard of it. But then again I don’t do this type of work.

But I found this on the web–it appears from this that it is to be put on top of the insulation, but it also reads like you could put it on the underside of the roof too.

http://www.ornl.gov/sci/roofs+walls/radiant/index.html

and

http://www.ornl.gov/sci/roofs+walls/radiant/rb_04.html

there is an email link on the page–perhaps you could write to the author of the paper.

4

Thanks. I read through it, kind of over my head, but I’ll try contacting the author.

5

Just curious-did you tell the city that this is to be placed ATOP the existing roof assembly? Has a PE evaluated this plan? Obviously, in Hollywood, snow loading isn’t a big consideration, but just the same, I’d want to make sure the existing framing can properly support what in essence is another roof assembly atop it, gravity being a dependable fella.

Quite honestly, if you contacted me and requested a quote to do the job, I’d be on the phone to a technical representative from Dow, or Johns-Manville, just to make sure that all of the installation details were clear before I proposed the project, much less started to build it. Rather than asking us, I’d go to the people whose product you intend on using, to see what they have to say. You might find out about a cheaper and more effective way of accomplishing your end goal, and at the very least will learn how not to eff things up.

Good luck.