Affordable R-30 walls with thermally broken T-studs
I have used the following wall system on several additions and recently on a 700 sf cottage.
Pretty simple system for small SIMPLE houses and additions. Maybe too labor intensive for huge,
complex houses. I'm in Climate Zone 5, Colorado Front Range.
Framing is 2x6, 24" OC with taped Zip Panels. No exterior foam. Strips of 1.5" foam are tacked to
interior side of all studs and top and bottom plates. Next, 2x4s are screwed flat to all exterior studs and plates. I used 4.5" screws, 3 per stud and one per bay for top and bottom plates. Add 8.5" of dense packed cellulose for R30. Effectively I have a 8.5" T-shaped, thermally broken stud.
-Avoids all problems and issues with exterior foam.
-Avoids problems of dense packing open stud bays
-Foam strip and 2x4 can be added any time, so does not delay construction or window setting.
-Dry wall hangers have 3.5" for drywall seams.
-Interior trim crew has continual backing for base.
-Homeowner has 3.5" target for hanging pictures.
-On kitchen exterior wall we ran horizontal 2x4s for continuous cabinet backing.
-Only thermal bridging is 4.5" screws
-R30 (Code Plus 50%)
-I'm not an engineer, but it adds stiffness to stud wall and prevents studs from bowing
-Still uses foam (4 sheets on 700 sf project)
-Somewhat labor intensive
-Added 600 lf of 2x4 (could be FJ 2x3)
-Thermal bridging of 300 x 4.5" screws (and cost)
Additional framing details:
-Single top plate -2 stud exterior corners
-All headers are in the roof system, not in the wall
-All windows and doors layout on one existing stud, fewer trimers and king studs.
-Used 10' Zip Panels for 8' walls, so no gap at floor/wall and wall/roof
-Glued or chalked all panel seams (Plus Zip tape)
So what is the question?
Can anyone calculate the thermal bridging penalty of 4.5" screws in an 8.5" wall?
Posted Mar 14, 2017 4:10 PM ET
Edited Mar 15, 2017 2:18 PM ET
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