[Greenbuilding] To Vent or Not To Vent? That is the Roof Question

[Lynelle Hamilton]

Again, I tap the expertise of this list.

I've read ++articles on venting vs not venting a roof.  This is my 
situation:

Shed roof.  High side is pretty much south facing; low side is north 
facing.Pitch is 4/12.  Roof is standing seam steel, light grey in 
colour, on strapping over ply. House is Durisol, 1940sq ft.

18" truss depth at the minimum.There is a cross member at the high side 
of the truss approx 2 feet down as well (giving me a 9ft ceiling on the 
south side of the upper level.

Climate is standard mid-Ontario (e.g. cold climate). We often have 
extreme NW winds (off the lake) that will hit the low side of the roof. 
Haven't seen Toto or Mary Poppins fly by yet, but would not be surprised 
if one or both did at some point.We get lake effect rain, snow and wind. 
When it rains, the rain usually pelts from the N-NW.

I can take extreme care to seal the living envelope to minimize air 
leakage to the roof, but am uncertain as to whether or not to vent the 
roof. I have thought of the following:

2" closed cell foam under trusses/underside of roof decking, then 
balance of cavity with cellulose, using blocking or batts to prevent 
settling at the low end. This should give me an R65 at the min. depth, 
more in the dropped areas in the upper bedrooms.

Amy advice on this is much appreciated.

Lynelle




---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/greenbuilding_lists.bioenergylists.org/attachments/20171105/6c861422/attachment.html>