How do I tape Tyvek to the ceiling air barrier?
mikeolder
| Posted in General Questions on
This is a gray area for me here in climate zone 6.. I want to build 2×6 Bonfiglioli walls, with raised heel engineered trusses over them.
What’s the most cost effective way to install a continuous exterior Water/Air barrier, over to the ceiling air barrier? No spray foam please..
I thought about wrapping the tyvek over the top plate before the trusses are set so that I could tape the ceiling poly to it before the ceiling drywall is installed. But doubt my framers will be to happy about walking top plates with tyvek wrapped over them.
Thanks!
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Replies
Mike,
I would think something as shown here would be a good fit:
https://www.finehomebuilding.com/2014/03/05/a-practical-air-sealing-sequence
It sounds a bit like you're using tyvek as your air barrier? The recommended advice here is generally to use the sheathing, as detailing tyvek as an air barrier is tricky and less reliable.
The key would be adding sealant at the sheathing-to-top plate connection, and then carrying that top plate (or plywood cap as shown in the link) over to your ceiling air barrier with tape or more sealant.
*I'd use a flexible sealant rather than a rigid adhesive
The way I've done is is to use a wide piece of peel and stick over the top plate. You remove only 1/2 backing and stick it over your sheathing and top plate and leave the other half dangling on the inside.
Once the trusses/rafters are in, install blocking between them and staple the peel and stick to it but don't remove the backing. You then install your interior poly under the rafters. Peel back the other half of the backing and stick the poly to it.
Once the ceiling drywall goes up it all gets sandwiched against the blocking. With this setup you don't have to strap out the ceiling as the link above.
I would also 2nd Tyler's suggestion. You should detail your sheathing as your primary air barrier. Getting Tyvek air tight is very hard, taping the sheathing is much easier.
I like that.
Does this mean you stop your sheathing at the top plate (to lap onto with the peel and stick) and then add scabbed on sheathing to the truss heels afterwards?
I'm not in wind or earthquake area so sheathing generally stops at the top of the walls.
If you need to add more sheathing higher up might be best to stop the sheathing a bit bellow the top of the wall so you have something solid to nail the scabbed pieces to. You can still do the air sealing with the tape as above, the extra pieces just get nailed over the flashing tape.
Thanks guys..
I had planned on using the sheathing as the main air barrier and Tyvek or even Felt as the the rain coat. But I haven't researched what brand or system for the sheathing flexible sealant.
What brand air barriers or system should I consider here in Iowa and are any top brands available in my area? And whats the disadvantage using a good brand of construction adhesive to secure my sheathing compared to a flexible sealant?
Adhesive sounds so much stronger here in tornado alley.
Mike
Mike,
There are specific strategies to strengthen your house against tornados, earthquakes, and hurricanes. Each is quite different. I wouldn't choose products for my air-sealing based on structural concerns, or vice versa.
Yeah, you might find an adhesive that's fine. I mentioned flexible sealant just to be clear that—if its primary duty is to perform air sealing—some adhesives may not be ideal for this (brittle, crack, and allow air pathways). Basically what Malcolm said.
To be clear, I can't and won't advise on protecting your structure against tornado's.
Also consider tape. A sealant may be needed in areas for a strategy like the one described in the article I linked, but you could possibly use all (or mostly) tape. It is pretty standard to create an air-tight sheathing layer with primarily tape, and strategic sealant as needed. There are quite a few good tapes out there today (Zip, 3m, Siga, Pro Clima, etc). Some builders may still prefer sealant, however.
You have a lot of options with the WRB (rain coat). If it's decoupled from the air-barrier as suggested, it allows you to choose from a wide variety of adequate products: https://www.greenbuildingadvisor.com/article/the-complicated-role-of-a-water-resistive-barrier
There are two distinct items here.
The structural adhesive is only there to connect the panel to your framing. It can help with air sealing but that is not its main purpose.
Air sealing is typically done with sheathing tape or a mastic. Tape is generally much quicker to install.
Thanks again everyone. This discussion has been thought provoking.
I knew as soon as I started figuring out details, my 2×6 Bonfiglioli wall would start to become complicated considering I don't work in the industry anymore.
I like the plan of extending/adhering 4x10 sheathing all the way from the rim joist to the truss heels and feel strength trumps air sealing in my high wind no code county. But that would mean setting trusses on walls without sheathing.. Sorry my question has taken another direction..