How’s my Insulate Attic Plan?
I have a 1950’s Zone 5 house. Since I have sealed combustion furnace/air in attic, I’m considering to insulate the the sloped ceiling (putting the attic space into conditioned space). It is a vented roof with 2×6 roof rafters. I would use:
1. GBA site-built-baffles out of 1″ polyiso (reflective side down) with 2″ air gap between roof sheathing and baffle
2. Plywood gussets connecting 2×6’s to 2×3’s for a depth to take R-38 batt insulation (maybe use two perpendicular layers of R-19 depending on cost)
3. For thermal bridging, I would cover the 2×3’s with another layer of 1″ polyiso (reflective side down).
4. Since there is no space to build out rafters with gussets around the furnace, I would use something like four layers of 1″ polyiso between rafters (1.5″ baffle to sheathing depth) and another layer of 1″ polyiso over the rafters if it fits. (I have access to 1″ polyiso or 2″ EPS.)
Q1: How does this plan sound to you?
Q2: Is it worth the expense to do this if I already have R-19 batts between joists and R-25 over that perpendicular to joists? In other words, have members/others found a benefit to justify such work?
I don’t mind the labor if the benefits will be noticed. Maybe there are some other options/plans of improvement. Thanks
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