A couple of questions for general knowledge

Old 05-28-11, 08:13 PM
Yukon Youngun's Avatar
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Question A couple of questions for general knowledge

I think I have seen these questions raised in this forum before but not definitively resolved, so I would like to ask them today to see if I can have them settled for me.

First, when I have seen faced fiberglass batts installed I have only seen the side tabs stapled to the inside face of the studs. It also seems clear that open air space within the stud bay is an avenue for air movement and thus unwanted heat transfer. So wouldn't stapling on the front stud face, behind the drywall, make more sense for better performing insulation by eliminating the obvious air space left by the staple tab?

Second, it seems to me inset stapling would also allow for more vapor penetration, via air leakage as well as through the wood itself. Wouldn't overlapping the tabs on the front stud face also provide a more effective vapor barrier because it would be essentially continuous, more like using a poly sheet?

Finally, vapor barrier in the ceiling or not?
Old 05-28-11, 08:34 PM
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As far as what I read, and my union carpenter friend said,

Stapling on the inside is preferred by drywallers. The edges of the studs are easier to locate. Some building codes, in this area anyway, require you to overlap the flanges, and staple them to the front of the studs.

The Correct Way to Staple Wall Insulation | eHow.com

As far as air space and what not, I dont know.

Mike NJ

Last edited by lawrosa; 05-28-11 at 08:56 PM.
Old 05-29-11, 12:46 AM
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Insulation does not stop air movement. It's job is to provide a thermal break only. Depending on the climate condition, a vapor barrier is used to stop air movement, whether the barrier is inside the insulation, or outside of it depending on the yearly temperatures. Hot climate, cold climate etc. In cold climates this is why products like Tyvak are used on the outside walls and still allow for moisture to breath out, but do provide some additional air flow control. In cold climates the vapor barrier blocks cold air flow meeting warm moist air on the inside of walls that can cause condensation. In hot climates the vapor barrier blocks warm most air from flowing into cold inside air, also helping to eliminate condensation. Air will flow through all batt insulation, blown insulation etc. The exception is sprayed closed cell foam, with BASF products like 'walltite' which do provide both a thermal break and vapor/air flow barrier and do not require additonal poly protection.
Old 05-29-11, 03:59 AM
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Well Yukon, I think you now have more confusion to add to your list. Your questions are perfect, but the above two answers illustrate just how new science and old habits can get mixed into a whole new set of guidelines and, so the above posters do not think I am picking on them, they are among the majority.

For your three questions: #1. yes staple to the face, #2, inset stapling reduces the overall quality and performance of the insulation. #3 In Missouri, yes.

Location and performance of these vapor barriers will change by region and climate, so specific answers may be different.

Rather than having me try to sort out all of the confusion, search "building science thermal barriers" and enjoy the reading. Once you find one of their articles they will lead you to others.

I will gladly get more specific on any of these issues if needed.

Old 05-31-11, 10:23 PM
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While there will always be confusion over climate and zones, when to and when not to, and the logic behind regs and codes, this time I think I am hearing consensus. First off, I might have suspected that the stapling method was a shortcut for someone. Contractors don't have the time to spend trying to find hidden surfaces like I would (as an admitted perfectionist). Since there doesn't seem to be any technical reason for me to change my preferred method, I figure I'm good. And actually, this exercise suggests to me that I should probably be stapling to the front face of the top and bottom plates as well, which I have not considered before because I had never seen it done.

And while equinox's explanation was quite thorough (and understandable I think) about the general application, the air flow I referred to was 1) the full length, unobstructed path next to each stapling flange and 2) leakage past the flange where it is not pressed (or sealed) fully to the side of the stud. The first condition allows free convection flow right up the warm side and into the cold side if not sealed at top and bottom. The second condition may be much less, but still allows air to find its own way through. But attaching to the front face would pretty much assure a tight seal (overlapping of the flange and pressure from the drywall) and eliminate the large vertical paths altogether. If fastened to the top and bottom also there is nowhere for convection to operate across the barrier, only within the glass itself -- much slower.

So, if I've got it right, then the question is how much difference does it make? I have a whole exposed basement walkout wall to deal with before next winter. Do I move the flanges before I close it up, or not? Just my musings, not really a question.

Oh, about the ceilings. Mine have no vb and blown fg insulation above. But the one upstairs room has faced batts all round. Not sure what code is here, but will ask before I add more insulation.
Old 06-01-11, 07:29 AM
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Really? Drywall installers have a hard time finding studs when the kraft face is stapled to the front of the stud? What a bunch of knuckle heads. The studs are where the staples are.

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