Hello,

We are currently designing our new house and will begin construction this fall in climate zone 6B. Our goal is to build an efficient and durable structure. Unfortunately, in our area many green building techniques are still uncommon. I am new to this site and am looking for advice on our wall and ceiling assemblies.

Walls: Contractors in the area are not comfortable meeting the external continues insulation recommended thickness for our region (R11.25) and so we have moved to a traditional wall assembly with only cavity insulation. We want to avoid their interest in thin external continues insulation (R6) due to our moisture concerns. The compromise design we are considering is (from outside in) wood siding> 1x rainscreen gap furring strips with top and bottom vents and insect screens>air infil. Barrier/WRB> WD Sheathing> 2×6 studs 16” O.C.> R23 or R24 cavity batt or loose fill insulation> 6 mil poly vapor barrier> ½”GWB. Code in our location allows for R21 walls without continues insulation. Since we are not pursuing continues insulation, we want to beat that low bar with at least R23 cavity insulation.  Our biggest goal is to create a durable and low risk wall assembly that our contractor is comfortable with. Does the wall assembly being proposed accomplish this? Are there ways to improve it? Is the 6 mil poly being the vapor barrier the best option? Our home will be air conditioned.

Ceiling/Roof: Additionally, the ceiling/roof plan currently does not have a specific vapor barrier/retarder. The roof assembly being proposed is Gypsum wall board> R60 cellulose loose fill insulation> trusses> synthetic underlayment on OSB> ice and water shield at eaves> steal roof. Should there be an additional vapor retarder?

Other assemblies: Additionally, the home is being designed to have at least R19 in basement walls and R10 rigid foam under slab.

Thank you!

Nick