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zantar 11-17-2009 09:01 AM

Furring strips on peaked roof
Hi All,

Building a clerestory off my flatroof on the 3rd floor. It has a simple peaked roof, each side being roughly a full sheet of ply. Now, I've gone ahead and nailed furring strips perpendicular to the rafters and 1/2" ply over that. My thought was that it would get lots of cross ventilation from gable to gable. Is my thinking correct? I'd rather not pull all that ply off! The insulation will be stuffed up to the underside of these strips, leaving the gaps between the underside of the ply and the rafters clear for ventilation. I'm hesitating now, because I started to wonder about convection, and if it has to run up to a ridge vent from the soffit as opposed to gable to gable. The way I've done it is easiest, but hopefully safe too in terms of moisture etc. Also, should I have put a building wrap immediately over the rafters before putting the strips on? There will be a vapour barrier between the insulation and the drywall inside. I'm in Toronto = cold..

Thanks all!!

Ron6519 11-17-2009 06:11 PM

To get cross ventilation you would need to leave the ends open. How do you plan keeping out rain or snow?
Typically in this construction, the furring strips would mimic the rafter direction. The natural convection would move the hot air up the roof and out the ridge vent. You just need to provide the bottom openings so you have a good intake.

zantar 11-17-2009 08:19 PM

I was just thinking that I would vent the soffits at each of the gable ends. There is definitely a clear passage from side to side.. I dunno- it just seemed to make more sense at the time.. Do you think it is a bad thing though? A flat roof can vent in the horizontal plane, right?

Oh- about it being open on each end- no it would be vented from under through the soffit of the gable eaves then across the top between the furring.

meboatermike 11-17-2009 09:35 PM

Can you post a picture --I am having trouble visualizing this but something does not sound right to me on the ventilation

zantar 11-17-2009 10:07 PM

2 Attachment(s)
Here's a few pictures.

Ron6519 11-18-2009 08:26 AM

So the design is to let in light and let out heat.
Well, the thing's already built. A little late for questions.
From a design prospectus, I would have made it taller, put the vents in the peak and put three windows across the gable end instead of blocking the largest opening with a vent.
I don't see how the flat roof gets vented into the structure.

zantar 11-18-2009 09:46 AM

Yes it's already built. There are (or will be when they arrive) three windows across the gable though. The smaller ones will be fixed and the larger middle ones will be casement. The window config is intended to let in only north and south light. Also, I just don't want a huge protrusion on the top of my roof and on the other end of the scale I didn't want a skylight. I do hope it will help with household ventilation in the hot summer months.

So for me the only question is really about the venting of the roof, though I appreciate other design comments too.

The flat roof this thing sits on is vented otherwise (not visible in the pictures), which might be another discussion actually..

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