Sealing tongue-and-groove sheathing
kevinjm4
| Posted in Energy Efficiency and Durability on
How do you go about air sealing original tongue and groove wall sheathing? efficiently if there is a way. And there is no rigid foam used in this wall assembly.
And is it advisable to air seal the soffit to top of wall sheathing joint?
Thanks
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For a studio conversion from an old garage, I put peel and stick membrane on the outside over the t&g and covered that by the new siding. The inside was batt insulation covered with plywood for finished wall. You might need a vapor permeable peel and stick if it is in a house, it was not an issue here as it is not occupied all the time.
The top of the walls on the inside were then spray foamed to seal up the soffits and roofing (roofing will be unvented ).
This stopped all the drafts in the studio, works great as the is very comfortable even with the existing un-insulated roof (to be insulated on the outside next year).
If I would do it again, I would go with exterior rigid with taped seams on the outside as I would not have had to deal with batts and non standard stud spacing and could have left the 100 year old t&g exposed on the inside.
What is your climate zone? (It matters.)
Seattle, 4c.
And yes this is for a house. And there is soffit intake as well, closer to the gutter though, on a 16” overhang.
Thanks.
In zone 4C it's generally safe to use air barriers that are also vapor barriers on either the exterior side of the assembly or interior, but not both. If using a peel & stick membrane be sure to pay attention to the material stackup of the wall.
If you're not averse to using foam, insulating the cavity with open cell foam does a pretty good job of air sealing while remaining fairly vapor permeable.
HI Kevin -
I am assuming that you are talking about interior T&G wall sheathing? If so, you need to apply some sort of sheet good over the T&G, air sealing at perimeters, joints, and penetrations. And yes, air sealing at the transition from the top of the eave walls to the roof assembly is key. But that transition does not typically involve the sofft.
Best - Peter
I was assuming it was exterior t & g or shiplap sheathing behind #15 felt & siding.
Sorry wall assembly will be as follows... studs, shiplap(see below), tyvek homewrap, furring strips, siding.
I didn’t mean to make it so complicated, completely my fault because I didn’t know what it’s called.. the house was built in 1939, and what I’m talking about is the sheathing on the non-addition side of house, possibly original sheathing. It’s that thick. Maybe 1” possibly thicker, about 8” tall, SHIPLAP I do believe after some research, hung horizontally, dark brown in color. So, I’m merely asking when I go to tear off the hardboard/Masonite siding on that side of the house, how do I get a good air seal in that material. just as you would tape seams/joints in plywood sheathing, do you do the same for every horizontal joint in that shiplap as well?
Sorry for the confusion and thanks again for the help.
In zone 4C you can use either a fully adhered permeable membrane (eg Blueskin) or impermeable membrane (eg Grace Ice & Water Shield) on the exterior of the ship lap sheathing as both an air seal and weather resistant barrier (no Tyvek needed).
If IM-permeable the interior finish needs to be reasonably vapor permeable (no vinyl or foil wallpaper, etc.)
There are likely to be some retrofit flashing details to attend to around windows when you do this.
If the wall cavities are uninsulated and you're not going to gut the inside to insulate them, blowing them full of cellulose drilling from the exterior would be a good idea prior to applying the air barrier.
Deleted
A tip on applying Blueskin (and similar fully adhered membranes) to walls:
"The VP100 was easy enough to install, but it’s definitely a two-person job because the adhesive backing does not come apart if you accidentally touch it to itself. Even though the wrap’s backing is split in half for easier removal, it can be tricky to get started, even when you fold a corner and rub the material back-to-back as the manufacturer suggests.
We ran most of the VP100 horizontally because we were working off pump jacks, but on the last wall I decided to install the pieces vertically, which is much easier. With gravity in our favor, we rarely had a piece stick to itself. And because the manufacturer doesn’t require any additional steps for vertical installations, this is how I plan to install it in the future."
https://www.finehomebuilding.com/2016/09/14/self-stick-wrb
Returning to an old thread… WITHOUT air sealing shiplap sheathing at all, how would one get a watertight window install with all those horizontal shiplap joints running into the window? Is it even possible?
kevin,
The sealing against water intrusion is a different process to air-sealing, and occurs at the WRB, not the sheathing. With board sheathing you layer the house-wrap and tape just as you would if the sheathing was OSB or plywood. Here are a couple of examples:
https://www.youtube.com/watch?v=JhXx__AMzTo
https://www.youtube.com/watch?v=SqP4liutJFs
I guess I even think about if/when moisture/water get behind the wrb. Once it gets to wood sheathing, if it’s cdx, you have (in my situation) a nail fin caulked at top and sides with good squeeze out. And no joints in the plywood to deal with except maybe a vertical joint or two in your window. With shiplap you have a number of loose 100 year old horizontal shiplap joints for possible water intrusion no matter how well you caulked the nail fin. Or is that way overthinking it and that just won’t happen…
If you didn’t gather as much I like to caulk and tape my window against the sheathing, then wrap the wrb over the window flange then tape again. Wrapping house wrap into penetration never made sense to me. I like the second video you linked to. Even in that video they allowed for skip taping at the bottom of the wrb, and I’ve always assumed the allowance for this means moisture *will* get behind the wrb, hence the question about shiplap vs plywood.
Kevin,
I built much of my own house with board siding. It's maybe not as easy to detail windows and doors as when you use sheet goods as the sheathing, but it's done successfully all the time.