semi rigid insulation over existing tyvek air barrier
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| Posted in Energy, Heating & Insulation on
Is it wise to apply semirigd insulation over top of tyvek (TYVEK over OSB)?
Replies
What is 'semi rigid' insulation? Either it is rigid (board type), blanket type, or loose fill type.
Hard to say ... what motivates you to do it? What type of insulation? Generally, the tyvek's job is to protect the thermal envelope from air/wind movement. Putting it under the insulation would be theoretically counterproductive. However, rigid insulation, generally tends to be an air barrier itself, so it's a LITTLE of a moot point (air leakage around seams are the exception).
Time and place for everything, though. Give us more details ... better details, better education.
It's not a problem, per se, but as Clewless suggests, one wonders what kind of insulation you're putting up, and why.
foam board over tyvek
Hi guys
The addition of rigid insulation over tyvek is an after thought to boost Rvalue and help reduce thermal bridging. To my way of thinking it would boost airtightness as well. I guess the only concern revolved around any trapping of moisture in the wall assembly .Our average winter temperatures here would roughly parallel Northern Michigan.
insulation over tyvek
P.S. The insulation is called Plastispan - a white beadboard with foil backing on one side and a poly film on the other.Their products are online.Cheers.
It will reduce thermal bridging. I went to the website ... they talk about 'effective R-value' ... an instant turn off in my book, although they didn't dwell on it and try to make claims for an R-40 out of 1 inch of their product. Everyone knows that insulation between framing results in thermal bridging at the framing. Everyone knows that using a rigid insulation on the exterior will help minimize the thermal bridging. It won't boost the air tightness measurably, I don't think. I don't think you'd have any additional moisture issues whether you place that product under or over the Tyvek. Your insulation is rigid insulation ... maybe it is thin enough where it doesn't feel like rigid ... but it is expanded polystyrene ... generally considered a rigid insulation.
And in fact they claim the stuff is rigid enoug to use for sheathing.
Off topic...
(I've often wondered how hard it would be to kick ones way into a house with vinyl siding over foam sheathing, fiberglass insulation, and drywall. Not sure you'd even need a hammer or something to use for a club.)
Off topic II
Dan,
Shortly after we bought our current house, a small new subdivision was under construction nearby.
They were building with stick framing, foam sheathing / insulation, drywall and vinyl siding. Into the resulting structures they were installing insulated steel doors with steel jambs. Big sign out at the entrance, which among other things, said " Ask about our security features!"
Being a wise guy, I stopped into the model home one day and asked. The sales person proudly showed me a sample entry door and explained that all of the windows and doors were already wired with alarm contacts and the wires brought to the basement ready to be connected to the security company's control box.
I asked " If I was a burglar why would I bother to go through a window or door when I could quietly cut through the wall alongside of the door with a utility knife and completely bypass the alarm system?"
Salesperson did not have an answer, and I left her wondering how to answer that question when a "real" buyer came in the door.
Jim