Smart vapor air seal or WRB air seal between shop and house?
I am looking to place an air barrier between an attached woodshop and a house. The shop is attached to what used to be the exterior of the house (circa 1916) which has horizontal board sheathing.
My question is what might be best to seal this. My project already involves Solitex Mento 1000 WRB on and Intello + for the shop.
My initial thought was to use the Intello on all four walls, including where it attaches to house, but I realized the conditions there are different and Intello is pricier than Mento (and other options).
Generally the house will be kept warmer than the shop (probably anywhere from 5-15 degrees cooler in the shop) and I expect the house to have higher air borne moisture content (shower, etc). I can’t say for certain that the shop will be bone dry though, as there might occasionally be some green wood and water based finishes.
I am undecided on insulation between the two, but will likely ‘update’ with some DP cellulose for sound (but not more than the existing cavity thickness of 3-4 inches. Insulation in rest of shop is DP cellulose at 10″.
My feeling at this point is that the WRB is vapor open (not intelligently) and that would be best given that both areas are conditioned and seeing uncertain humidity levels… ?
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I should add that there MAY be a future retrofit of the house in which it becomes significantly airtight, but it currently is... not
The shop is being designed to be air tight, hence the reason to seal between them (and for possible air borne contaminants).
I haven't ruled out sealing this area with plywood and tape either...
Tyler,
Air sealing is always good. Pay attention to airtightness when doing this work, especially at penetrations.
The vapor permeance of any membrane used here isn't very important, since there isn't much of a temperature difference between the two sides of the partition -- nor is there significant vapor drive. So you don't need a smart vapor retarder (although there won't be any problems if you decide to install one).
If you have drywall or plaster on one or both sides of this partition, the drywall or plaster is a perfectly adequate air barrier. What matters is penetrations-- so pay attention to electrical boxes. Otherwise, don't worry.