[Greenbuilding] Insulating a cathedral roof
Lynelle Hamilton
lynelle at lahamilton.com
Wed Dec 27 18:53:42 CST 2017
Hi Listers,
My new build has a shed roof with a 4:12 pitch; low side on the north.
It is a trussed roof. Trusses are in 2 parts (lengthwise) with an
approximately an 18" depth. House has a partial second storey, extending
over the entire south facade and part of the north facade.
Interior, there is a cathedral ceiling over approx 60% of the north side
of the house and 100% of the south side (second story). The remaining
40% of the north side is used for storage and would have the potential
for a wider range of insulation options.
Roof is standing seam steel over ply with ice and water dam over the
entire surface. Two stack vents penetrating (one 6' from the high side
and another 16 feet from the high side. One chimney penetration either
16 feet from high side OR 4 feet from low side.
Trusses sit on top of 14" Durisol.
I've read a ton and talked with local builders (many of whom think R-65
is overkill and I am crazy). There is no consistency in approach. I am
no further ahead.
Thus, I have a few questions:
1. Vented or unvented roof?
2. Either way, I'd like to sock at least R-65 into the cavity. What's
the best way to do this?
3. Should I isolate the truss from the wall top and if so, how? Rigid
Roxul? Gasket?
Many thanks for any expertise the group offers.
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