Viability of this Assembly
AmandaCDH
| Posted in Green Building Techniques on
I’m researching a proper envelope for climate zone 6a. I own a 1949 ranch with cedar shingles installed over roughly 1 1/2″ fiberboard sheathing (2 layers–1″+1/2″) over conventional 2×4 framing with no stud bay insulation. I am wanting to greatly increase my thermal envelope. My fiberboard is in good condition but I do plan on removing the cedar shingles (temporarily) for needed repairs and to add exterior insulation. This is the layering (interior to exterior) I have in mind and am seeking thoughts on its viability:
Latex paint
Gypsum
Blown cellulose 2×4 stud wall
1 1/2″ fiberboard
Vaper/air membrane (??)
4″ rock wool
4″ rock wool
Horizontal furring strips at 5″ increments
Cedar Shingles
I would like to stay away from petroleum products. I also want to make sure I am not trapping moisture in the wall cavity or on the sheathing.
Thoughts??? Thx
Thoughts??? Thx
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Replies
Here is a good reference for walls with exterior insulation.
https://www.continuousinsulation.org/content/2021-ibc-and-irc-adopt-improved-vapor-retarder-requirements
Tyvek is a common WRB layer.
Which climate zone is this for? You have all the basics, just need to pick a good WRB that is installed correctly. Watch the flashings around the windows and don’t plug any drainage holes.
I am keeping my original wood windows so I guess they will be considered "innies". I'll be sure to educate myself on proper flashing.
Zone 7/cold (6a is my gardening zone). I'm not a huge fan of Tyvek housewrap-all the fastener holes would seem to compromise it. I'm leaning toward a self-adhering variety. Any recommendations?
Just detail your sheathing as air barrier and tape the seams, then do Tyvek.
With Tyvek behind exterior insulation and a rain screen it'll be golden.
Blueskin VP100 is often mentioned.
Look for Michael Maines and Michael Chandlers comments around some of the WRB. They have replaced some SA type material.