[Greenbuilding] Insulating a cathedral roof

[George Tremblay]

Joe Listiburek's Building Science website
<https://buildingscience.com/document-search?topics%5B0%5D=707> has some
info that might be helpful to you.

On Wed, Dec 27, 2017 at 7:53 PM, Lynelle Hamilton <lynelle at lahamilton.com>
wrote:

> 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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