Reality check: I don’t think there’s anything wrong with this, but just checking….
Insulating a wall that I don’t want to finish (running wires across studs etc). Putting insulation (cotton w/PDBEs) into stud bays. Then plastic VB (I’m in NE) sealed with caulk (wasn’t going to do this, until wind started blowing insulation out of the stud bays!). Now want to protect this VB from UV and general wear, and DW too much of a PITA, so I’m putting #15 felt paper over it.
I don’t think this combination is a double VB. Felt paper used all the time as a semi-permeable air barrier outside sheathing, with a VB on the inside, some even prefer it to Tyvek. I also feel comfortable putting in VB because this space will never be air-conditioned. But just checking….
Replies
I don't think I like what I'm reading.
A) Plastic vapor barriers aren't usually that great of an idea (northern Minnesota and much parts of Canada notwithstanding)
B) Wind keeps blowing the insulation out of the stud bays. I don't like the sound of that at all.
(Sounds like we need to publish that article about air barriers vs Vapor barriers). But in the meantime, read the article we did in issue #160 "Does Fiberglass Insulation Still Make Sense?" By Scott Gibson. We talk about how air movement affects insulation performance and we touch on the vapor barrier issue. Tell me more about the wall assembly. You don't intend to finish the inside, so where is the wall, attic, daylight basement? What's your exterior cladding and what's the sheathing? Any type of building paper?
But most importantly, where do you keep the beer?
One happy assistant editor
Edited 4/4/2005 7:06 pm ET by Dan Morrison
The important questions first: Sammy Adams in the fridge. Help yourself!This is an unfinished attic. I'm putting a subpanel in, there'll be wires running along the gable wall, so I want to get any insulation finished before I put the subpanel up. The house is 75 yo, sheathing is I guess some kind of T&G 1x, and sometimes they even got the T in the G. If there was ever tar paper outside, it's long gone, I can sometimes see daylight through the wall. I may install new air barrier eventually as part of residing (currently cedar shakes) and putting insulation into the stud bays.Reason for insulating attic: There's an air handler in the attic, and it's a walk-up attic. I don't plan to bring it into the envelope, just make it more of an intermediate zone. The gable walls now, the rafters later (maybe foam panels on the rafters as baffles for the vents).Reason for VB: PO had put blankets over some of the more egregious gaps in the wall. When I took them down, the sheathing was wet, and it had not rained in some time. It made me a believer in VBs. The new insulation is like thick comfy rugs, I could see it getting soaked with moisture from air vapor in winter. In general I'm leery of VBs that are on the wrong side in summer, but as I said, this space will never be air-conditioned. Reason for caulking: Primarily as a glue to hold the VB to the studs. I tried stapling but the plastic is tearing around the staples. Secondarily to seal the insulation from the moist internal air.I understand the difference between air barrier and vapor barrier. I'm not installing an air barrier, I realize that should be outside the sheathing. I'm just using tar paper as the quickest and easiest way to protect the VB primarily from UV. I'm rationalizing that it's safe based on the fact that building codes typically call for combo of VB and AB.
Taylor,
>>quickest and easiest way to protect the VB primarily from UV
You have sunlight in your attic?
You need a lot more than just your Gable Ends insulated.
SamT
Windows on gable end walls.....Know how to get a DH window functioning again when it probably hasn't been opened in several years/decades? Looks like it has *never* been painted....
why don't you just cover the windows?
I like daylight when I can get it.Anyway tar paper's up.
Reason for VB: PO had put blankets over some of the more egregious gaps in the wall. When I took them down, the sheathing was wet, and it had not rained in some time. It made me a believer in VBs. The new insulation is like thick comfy rugs, I could see it getting soaked with moisture from air vapor in winter. In general I'm leery of VBs that are on the wrong side in summer, but as I said, this space will never be air-conditioned.
Are you alking about those batts that are inside vinyl pillows? They were installed only over a few stud bays? And the stud bays they were installed in were the only ones that were wet?
Dan
Dan Morrisonassociate editor
Edited 4/7/2005 6:37 pm ET by Dan Morrison
No, it was just ordinary blankets that someone had nailed over some of the gaps in the sheathing. When I took them down, the sheathing was wet where the blankets had been.The installation instructions for the cotton insulation call for a VB, to be put in immediately after the insulation is installed.