Opinion and questions on details of European flangeless windows – GreenBuildingAdvisor

Hi All

I have searched extensively online, and I feel the following would be the best strategy to have a good air and water sealed “middie” windows in my planned thick wall for a new construction. I’m in Climate Zone 5A.

My wall from inside to outside would be as follows.

Drywall

2″ x 6″ studs with R23 Rockwool Comfort Batts

7/16″ Zip sheathing

3″ Rockwool Comfortboard 80 (R 12.6)

1″ Furring strips

Brick veneer + trims with steel or Hardie sidings

Thickness of insulated portion is 9″ 7/16.  And then furring strips. So, the window buck thickness would be  9″ 7/16. I plan middie European windows. So, it would be in the outer half of my studs – kinda middle of the buck.

The attached 3 pictures summarize what I am planning to do. The first two pictures of making a window buck and then flashing it are from kimchiandkraut.net. The last picture is a screenshot from a youtube video by NS Builder. It was interesting to see self adherent WRB (SIGA Majvest) being used as flashing.

Questions:

1. What is the best material to make a window buck?

a) Wood

b) Something like Zip sheathing (7/16 vs 1/2 vs 5/8″) which can provide an air + water barrier on the inner surface of buck, thus minimizing tape use

c) use a study material like advantech subfloor

2. Is adding an acoustic or a watertight sealant (e.g Lexel) between the attachment of window buck to the jack stud needed?

3. Is flashing using tapes (Zip tape, SIGA fentrim or Wigluv) better than using a liquid like Prosoco fastflash or Zip liquid flash?  In terms of durability and costs…

It was interesting to see SIGA Majvest used for flashing by NS Builders. It is not recommended to turn at corners, so maybe cost saving if window bucks are very thick…

4. If I use tapes, do you think the Zip stretch tape would do well with flashing the outer 4 corners of the projected bucks, plus the 4 corners where outer surface of the bucks meets the zip sheathing on the wall. In videos where I see Zip stretch used, the window opening outer edge is flush with the Zip, so it goes over the sill pan, jamb, and then on the flush Zip.

5. To make the windows air and watertight, which method is better – in terms of durability and costs.

a) Backer rod plus sealant (e.g. Prosoco airdam) along all inside perimeter, plus SIGA fentrim on outside perimeter except the bottom

b) SIGA fentrim both inside and outside (except the bottom)

6. To get some extra insulation, can I place some rockwool Comfort Batt strips on the perimeter (except the bottom) before doing air and water sealing?

Any other thoughts are much appreciated.

Thank you so much in advance.