Celling insulation issues, ventilation...

[NewLogik]

I need some suggestions from you guys, I known I should have done something different before, but now I'm stuck with my celling insulation. We added 2.5 feet to the roof last year and we didn't managed to get some kind of ventilation like we should had....

From the back of the garage I did installed some raffles as shown in the pictures, so it takes the air from the rear soffits, which is fine, but at the front of the garage there's no ventilation since the wall had 2.5 ft added but without any gap from the existing one where's the soffits are...

Now I need to do something, the roof framing is made of 2x12 , and insulation is R-40. I tought maybe I could do something getting ventilation from the front side top corner ? If I manage to get a hole to get air from there and somewhat drill holes in the top of 2x12 ?

Any ideas ? It would be much appreciated since I really want to finish this as soon as I can and I'll be stuck with that when I'm getting near the front of garage...

 

[NewLogik]

If you need anymore pictures or infos, let me know, again thank you alll for your help

 

[LowKat]

You need to ventilate each cavity between each rafter if it's getting a finished ceiling. I'd use a 1-1/2" speed bore drill bit and put 3 holes in each cavity near the top. The insulation needs to be held to the bottom of the rafter so there's an air gap at the top between the insulation and the plywood.

Then use something like this to cover the holes.

 

[Finnish Knight]

I may consider installing a ceiling at the top of the wall inside and then insulating the top of the ceiling. Open up your soffits (or somewhere lower than the vents) and install some whirlybird vents in the roof. You would then have some open area to vent above the ceiling. Of course, this negates the high ceiling then. There is also the vent free method where you can just spray foam the bottom of the roof from the inside and leave no ventilation. This means you need serious R value since you cannot allow any warm air to escape onto the roof. Disclaimer: I am no carpenter so I would also seek a professional opinion!

 

[NewLogik]

You need to ventilate each cavity between each rafter if it's getting a finished ceiling. I'd use a 1-1/2" speed bore drill bit and put 3 holes in each cavity near the top. The insulation needs to be held to the bottom of the rafter so there's an air gap at the top between the insulation and the plywood.

Then use something like this to cover the holes.

Not sure where you want to add thoses ? The rafter is on top of the R-40 insulation so we have from top to bottom, plywood(roof), rafter, insulation but there's no gap between the roof and rafter so no ventilation can be done from there ?

I tought I could manage to do something like :

What you think ?

Finish knight, thanks for your input, but as you said can't lower the celling since I'll lost the fact that I need more height for my 2 posts lift and some storage...

 

[LowKat]

is there an air gap between the insulation batts and the plywood so the air can travel the length of each rafter bay?

 

[NewLogik]

is there an air gap between the insulation batts and the plywood so the air can travel the length of each rafter bay?

The air can travel trought tunnels created by ther rafter, other than that, there's no gap... That's the instructions on the rafters. It said to staples them down to the rooft and then add the insulation right under.

 

[LowKat]

The ideal situation would have been to cantilever the rafters out past the wall creating a soffit. But since the front is already completed, I'd make a triangle shaped soffit using drywall or plywood. The area on the ceiling behind the soffit would be left open with no covering on the ceiling. Put your vent out the sidewall.

excuse my 'paint' skills

For the venting to be effective you need to have the same amount of area going out as coming in. Measure the vent area on the back of the garage and try to match the same amout in square inches on the new sidewall vent. You could use a vent designed for a gable end.

 

[Finnish Knight]

Perhaps going to a ventilated fascia on each of end of the proper vents?

 

[NewLogik]

I'm not yet set on what I'm going to do... It will not look pretty to have some ventilated fascia on front, but will probably need to get at least 3 front ventilated fascia with hole between each cavity.

On top of that, we had a pretty big storm lately which resulted with the temporary garage where I stored the insulation was torn all arround which resulted in rain getting on the insulation package and now many of them are sodden / full of water !!!

Progress so far :

 

[Boomer343]

Have a look at this product, no experience with it but found it looking for a solution to anothe rroofing problem.

http://www.dciproducts.com/html/smartvent.htm

 

[NewLogik]

Have a look at this product, no experience with it but found it looking for a solution to anothe rroofing problem.

http://www.dciproducts.com/html/smartvent.htm

Really interesting product, but seems to be only available in USA... still a really good idea there !

 

[NewLogik]

I just saw that roofmart have this product, now need to verify if they have thoses in stock... Want to take a look at different models

 

[NewLogik]

Looking at different products right now, but I should find something, it's certainly going in right direction now with your suggestion Boomer !

http://www.gaf.com/roofing/residential/products/roof-vents/Cobra-Snow-Country/Cobra-Snow-Country.aspx
http://www.gaf.com/roofing/residential/products/roof-vents/Cobra-Exhaust-Vent/Cobra-Exhaust-Vent.aspx

Well the first one is for roof ridge usually, but anyways getting some ideas might help !

 

[NewLogik]

I really don't like the idea of installing some ventilation directly on the roof itself, It's a one side slow slope roof and it's brand new with 2 ply High resistance cap sheet membrane and I would definately like to find something other than a solution involving a hole in the new roof sheets...

Hope I'll find a really good solution soon Thanks again for all your suggestions/ideas !