[Greenbuilding] roof venting

[Clarke Olsen]

   Frank,
   Thanks; I watched that video (and more, of course). I thought that if the space was filled with bat insulation, the Roxul would
   be porous enough to allow the tiny amount of water vapor to migrate out through the sawn lumber of the facia/soffit. 
   Part of my logic assumed that with the space packed full, there would be little opportunity for fresh moisture to get into the joist 
   cavities, not enough need a drain. 
   Clarke 

On Jan 21, 2017, at 6:24 PM, Frank Tettemer <frank at livingsol.com> wrote:

> Hey Clarke, Here in Ontario there has been a cheap (but plastic!) product developed a decade back. It's a skimpy sheet of styro, like an egg carton thick, and factory-molded like an egg carton, to form a pair of ventilation throughways. These things get stapled to the underside of the roof, between rafters or joists, with the first one's "drip-line" outside in the soffit area. Each one stapled up is "shingled" in such a way that any moisture above the styro, eventually drips out the un-insulated but Vented! soffit area.
> At the peak of the roof, VicWest makes a fantastic metal box-like vented roof ridge, that carries ventilation from the soffit through and out the ridge.
> Styro rafter vents are called Moore Vents in this area, cover about 22" x 32" area, cost about a buck each.
> Put up batts, or blown in cellulose, those plastic vents do it.
> 
> ( Aside: Twenty years ago, addressing this same concern for condensation, I made up a batch of "Moore Vents" out of scrap wood and card board.
> Laborious. But no problems with it over it's life so far.
> I pay the dollar for the store-bought ones now, gladly.)
> 
> Here's a picture of the VicWest Vented Ridge, on page two, very bottom left corner:
> http://www.vicwest.com/sites/default/files/Res_SR_SnapRib_Ultravic_Install_Guide.pdf
> Here's a simple video of a guy putting the Rafter Vents up:
> https://www.youtube.com/watch?v=5DX25Vz2jDc
> 
> Frank Tettemer
> Living Sol ~ Building and Design
> www.livingsol.com
> 613 585 3661
> 
> 
> On 21/01/2017 1:02 PM, Clarke Olsen wrote:
>> I am building a 750 sqft building with two single plane (shed) roofs, using 12" I joists @ 3/12 pitch.
>> Can we just stuff that 12" with Roxul, or is ventilation needed?
>> Clarke Olsen
>> clarkeolsendesign.com <http://clarkeolsendesign.com>
>> 373 route 203
>> Spencertown, NY 12165
>> USA
>> 518-392-4640
>> colsen at taconic.net
>> 
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