Proper way to staple up insulation batts in flat roof?

[TomYoung]

Hi all:

Asked this before but didn't get a reply that specifically addressed the question so I thought I'd try again.

I'm putting up fiberglass batts in a flat roof, i.e., the ceiling is removed so I'm working inside the house. The roof joists are nominal

2 x 10's. The insulation that was there before had been pushed up into the cavity between joists and the flanges on the faced batts was stapled to the wide face of the joists, just above the lower edge of the joists.

My instinct is to staple the flanges on the narrow edge of the joists, overlapping flanges to create a more secure moisture barrier.

Is one way of doing the stapling better than the other? If so, how come?

Thanks.

Tom Young

[dpb]

TomYoung wrote: ...

You already answered your question albeit the difference is minimal.

--

[Tony Hwang]

Hi, Main thing is to keep the air leak(thru any gap) to minimum. Whatever makes air tight.

[Bob F]

I'd be tempted to add a layer of plastic before re-installing the ceiling to really seal it.

Would that meet code?

[Tony Hwang]

Hi, Vapor barrier?

[Rudy]

Thats the proper way unless the air space above the batts is vented somehow. You dont want to create an unvented air space above your batts which might be the case in a flat roof. If the batts are placed up against the roof sheathing, you dont have to worry about venting.

When they built our home in the AZ desert, they "wired" the R-30 batts up against the roof sheathing between the web trusses.

[Joe]

You didn't get the answer you wanted so you're asking again? Reread the replies.

Joe

[TomYoung]

No, I said I didn't get an answer that really addressed my question. Go read the *one* reply at

and see if you don't agree.

Tom Young

[Bob F]

Yes. And seal out any potential leaks.