335 Maplewood Ave Renovation: Air Barrier & Window R.O. Connection

The internal layer of Tyvek is our primary air barrier (remember? Check out the blog from 3/16 for some background). We are going to be poking huge holes in that air barrier for our window openings all over the place. How are we going to maintain our air barrier integrity with all of these giant holes poked in it? We need to create an air tight connection between the Tyvek air barrier and the windows somehow. We do not want any air leaking around the window openings.

We broke this detail down into two main connections that need to take place.
One connecting the Tyvek to the built out rough opening and a second connecting the built out rough opening to the window.

Connecting the Tyvek to the built out rough opening is where we had to put our thinking caps on. It is not a standard off-the-shelf detail. We wanted to figure out the most efficient way to make this connection work.

We looked into 3 different methods:

Option A - Cut back Tyvek

Option A - Lay down bead of caulk

Option A - Fold Tyvek into caulk

Option A - Lay down bead of caulk ontop of Tyvek

Option A - Install rough opening

Thoughts? - Lots of steps, caulking is sloppy... It would work but there has to be something better!

______________________________________________________________________________

Option B - Install rough opening and cut back Tyvek

Option B - Vycor Tyvek to built out rough opening.

Thoughts? - Much more buildable than option A huh? It appears easy to install & inspect. The Vycor adheres to Tyvek, wood & Adventech so the connection would have been solid. The only major downside is that Vycor isn't a cheap material.

(We were prepared to move forward with this detail until we discovered option C!)

________________________________________________________________________

Option C - Cut back tyvek

Option C - Install built out rough opening

Option C - Fold Tyvek down ontop of tyvek and cut back leaving about an inch behind.

Option C - Put up first layer of 1-1/2" rigid foam, leave about a 3/8" gap.

Option C - Great Stuff foam gap paying attention to getting a good solid fill and contact with Tyvek.

Option C - Install 2x3 trim nailer (securely screw into studs beyond).

The window trim needs something substantial to nail into. 1/2" Advantech is not enough.

I first thought that this sounded unnecessary because how much does a piece of trim weight? Not much, right? Why throw in this big sub assembly for something that weights so little? Why not just nail it into the Advantech and call it a day?

Well, this is why: The Bruss team felt confidant that the finish nails holding the trim down would fail without a sub assembly over time. (I believe them) If the nailes failed, it would be a disaster from a water management standpoint. We need to keep water out from behind the trim. We can't have the trim lifting and letting water get past the caulked edge of the trim.

Option C - Install second layer of foam, leave ~3/8" gap

Option C - Great Stuff foam voids on both sides of nailer.

Option C - Install final exterior sheathing.

The final connection that has to be made to make this wall assembly air tight is going to be between the window and the rough openings. Great Stuff foam is going to be used to make this connection. The Bruss team is going to simply fill the 1/2" crack around the rough opening from the inside of the building as seen below.

Pictures of Option C in progress -

We did a mockup of Option C and then took it apart to see how well the foam stuck to everything. We had to tear the foam off of the Tyvek. It stuck really well.