Wall section? Attic insulation? Energy / Moisture / Storm
I’m a licensed GC designing an addition to my personal residence which we built in the late 80s. The original house was built with 2×6 studs and might very well have been the first house built in NC with a sealed crawl space. (I gave my building inspector a copy of a sealed crawl space article by the TVA, and he OK’d the sealed crawl space.)
I would greatly appreciate some input on a couple aspects of the design.
Project consists of an addition (den / guest bedroom & bathroom) as well as an exterior renovation (siding, windows, doors, roofing) of the existing house.
Energy: NC Zone 4A, immediately adjacent to 3A. Energy goal is to get close to net zero with PV panels. Addition will include wood stove. We live on an 80 acre farm, 60% wooded, that typically generates more than enough firewood in a year to heat the house from down stormed trees, pruning, etc.
Storm Resistance: Guest bedroom / bathroom will be built to high levels of storm resistance, possibly to the levels of a FEMA Storm Room. The FEMA details call for a double layer of 3/4″ plywood with a layer of 14 ga steel for impact resistance, and FEMA rated storm doors and window shutters. I will not sell this house as having a “storm room” unless I meet all the FEMA specs.
The addition will be built with a crawl space (which is a variation from the FEMA plans) and a bonus room on the second story. The crawl space walls will be Ivany block with both vertical and horizontal rebar. The footings will be deeper, wider and thicker than required by code.
My initial questions are:
1) Re the wall sections for the guest bedroom/bathroom, will the following wall section perform well as far as energy / moisture?
From exterior to interior: Vinyl siding (200 mph rated) / Housewrap / 3/4″ plywood / Double layer of 1/2″ foam / 3/4′ plywood / 14 ga steel plate / 2×6 studs @ 16′ oc with unfaced fiberglass batts / GWB. I may go with a double layer of 3/4″ foam instead of 1/2″.
Would there be a better location for the steel plate as far as moisture control?
What type of foam would be best?
Since this wall section would have to have some drying capability to the exterior, what should I look for in a house wrap?
2) Re attic (story and a half semi-conditioned bonus room), would a vented roof system or sealed perform best?
The 1st story ceiling / 2nd story floor will be a full floor system with a perimeter band joist and floor sheathing covering the entire deck including band joist. Rafters will bear on a 2×6 plate on top of the floor sheathing. Overhangs at the eves will be “scabbed on”.
Roofing will be galvalume metal roof panels.
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