Pretty Good Wall Design - Maybe
The attached file shows a wall design concept for a new house build near Minneapolis, Mn. I'm trying to design a wall that is both easy to build and has good performance.
I really wanted to bury the air and vapor control layers at the sheathing layer so the stud cavity only uses 2.5 inch thick rockwool batt (I'm firm on the rockwool insulation direction). Approximately 3/4 of the insulation is on the outside / cold side of the vapor barrier to prevent condensation on the sheathing. This also leaves 3 inches open for a utility chase. One big installation advantage is that fitting the insulation around wires and boxes is minimized since the batt is usually behind everything - no cutting needed.
The sheathing and control layers could be lots of designs. One is the Huber Zip wall system. Second is taped plywood plus house wrap or roofing felt. The third is peel and stick covering over plywood. Fourth is a liquid applied over plywood. I'm leaning towards number 2 for cost reasons.
There is one layer of 3.5 inch rockwool batt. Since there are no studs here the thermal break is good and moisture can move sideways if needed.
The next layer is 2x4 studs, 3.5 inch rockwool batt, plus a high perm weather resistant barrier (ie #15 roofing felt shiplapped or house wrap). This keeps wind and rain off the insulation but allows some air and moisture passage.
Over this goes the 1x4 nailers. These create the rain screen vent behind the cladding, hold the insulation and WRB on tight, and act as a wide nailing surface for the siding.
The 2x4 studs are attached to the 2x6 wall at the top plate and sole plate - I haven't worked that out yet. They are cantilevered off the wall and hold the siding (so only the 2x6 wall sits on the subfloor). The two outer layers of insulation (outside of the sheathing) are entirely on the outside of the walls and floors to get a good, continuous layer of insulation and air/vapor barrier.
I intend to have windows and doors attached to the 2x6 wall and sheathing just like a normal wall.
OK, so what do you think? I'm cautiously happy with this approach and how it balances performance, construction, longevity, and cost. All feedback is welcome.
|Wall Layout 1.pdf||17.33 KB|
Posted Sun, 04/20/2014 - 18:44
Edited Mon, 04/21/2014 - 07:14
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