[Greenbuilding] Unvented cathedral ceiling condensation

[Reuben Deumling]

A delightful article. Thank you for sending that, and very timely for me.
One thing that occurs to me when reading it is that we here in the PNW
whose humidity profile is basically the reverse of much of the rest of the
country, or at least of much of the rest of the inhabited part of the
country, tend to be forgotten. I don't know if it makes much difference to
these questions of moisture management, but it seems like it probably
would.

Finally I have to say this paragraph (which contradicts the rest of the
article) made me laugh:
*However, in some areas of the country, especially in the Northeast,
insulation contractors have been dense-packing unvented rafter bays with
cellulose for years. Because the method has deep roots in New England, many
building inspectors accept such installations.*




On Sat, Dec 10, 2016 at 11:50 AM, Leslie Moyer <unschooler at lrec.org> wrote:

> I have some nearby friends having a problem. I think I understand what the
> problem is, and even some possible ways to solve it, but I'm not certain I
> could give them advice that would fix their problem the best or cheapest
> way. I thought you guys could, though!
>
> They read this article & I think they will go ahead and pay to read the
> article referenced within it:
>
> http://www.greenbuildingadvisor.com/blogs/dept/musings/how-build-
> insulated-cathedral-ceiling
>
> We are considered a "hot humid" climate--NE Oklahoma
> …………………………….
>
> We have a question regarding condensation problems in a cathedral
> ceiling.  We live in northeastern Oklahoma (zone 3) and just added a
> dinning room (cathedral ceiling) 15 x 19 addition.  The addition was just
> opened up to the main house earlier this week, and we got hit with (what
> are for us) very cold temperatures.  Thursday night had a low of 12 F.  By
> noon on Friday we noticed that water was dripping down the north side
> interior wall  (along the drywall).  The drip lines appeared to be spaced
> every 24 inches, or about where a roof rafter would be.
>
> The ceiling/roof construction was constructed with 2 x 8 rafters and
> insulated with R30 Roxul (rock wool) insulation and is not vented.  The
> interior ceiling is wooden tongue and groove car siding.   The roof decking
> is LP TechShield Radiant Barrier (with the metal foil side facing the
> interior of the house, as described on the boards) with a metal roof (there
> is felt paper in between the decking and the metal roof on the North side,
> but on the South side we used double bubble).   We did not have any
> condensation issues on the south wall.
>
> We have spoken with over half a dozen different experts, and we’re getting
> as many different suggested solutions.  We are desperate to fix this
> problem and would greatly appreciate any help!  Thank you!
>
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