Attic ventilation for gambrel roof


#21

A cold roof is another roof framed over the top of your existing roof.

For a cold roof.
Tear off the existing roof, repair any deck damage and cover with underlayment, regular old felt is fine but you can use any underlayment you wish.
Lay 2"x4"'s over the existing rafter/trusses and secure them with nails or screws.
These 2"x4"'s that were just laid down will provide for 1 1/2" if clear space for airflow.
Sheet over the 2"x4"'s and proceed as usual.

For intake ventilation you can use some vented drip edge at the pitch transition.
Now the air will flow between the 2 roofs with no blockage.
Your original roof deck is now the warm side and the new roof deck that was framed over the old is a cold deck.
Any heat or humidity that emanates from your home will be vented between the 2 roof decks.
So in theory the new roof deck never gets warm enough to create ice dams.

Constructing a cold roof is usually pretty easy and straight forward.
Since 2" of height has been added to your roof there will be some facia work that needs to be done.
Instead of re-doing the facia sometimes you can just use a bigger edge metal to cover the extra 2", it depends on the home and what look you prefer.

This type of roof construction is ideal for cold climates.


#22

Wow. I will discuss with the roofer. I don’t know if I can come up with enough money to do that this year, though. I’m guessing it ups the price a bit!


#23

Yes it will cost more but something better usually does.
It is 1 more day of labor and the cost of material.
Adding rafter baffles and smartvent cost more also.
It is worth the extra cost, it’s a permanent fix.


#24

Have an issue would like opinions from the group here.
Had a gambrel roof re-shingled about 4 years ago. The installers did not seem too prepared to provide adequate ventilation from the get-go. I asked for drip edge vent to be run along the entire bottom, and for soffit chutes to be run the entire “gutter-to attic” run. The chutes they were installing seem to simply crush and pretty much flatten out. I noticed this because they were replacing some decking so it gave a nice view of what was happening along the rafter runs. I asked if I might half some PVC pipe to put under the soffit vents to hold them off of the decking. So I got up in the attic and the guys assisted in getting the PVC in place in most of the runs. I then blew in insulation, taking care not to load the chutes (they were all extended pretty far up the rafter voids. Fast forward to this past week, I am looking at adding more insulation to another part of the house, and thought I would check the gambrel area while I was getting insulate dirty anyhow… Imagine my surprise when I see black and damp to the touch decking on the underside of the gambrel, as it comes into my attic. MOST of it seems to follow the underside of the baffles, as they extend toward the peak. Oddly, the few rafter runs where I was unable to place the PVC seemed unaffected. I removed the baffles that were completely above the bottom plate, used a bush rake to pull insulation back on both sides of the PVC pipe (best I could, seems the only real venting would come from the PVC). The underside of the baffles had signs of damp
blown insulation, where it looked liked it had condensated then dried. I now have a squirrel cage fan, pointing mostly upward so as not to blow the insulation around, and in the PVC, in an effort to dry out the underside. Should mention that the backside is not gambrel, shallow pitched normal roof, with drip edge vents as well (whole area has ridge vent, by the way), and there is zero issue on that side of the attic, or anywhere other than about 4ft up from top plate of gambrel.
I really can’t tell definitively, but it doesn’t look like it goes very far don into the gambrel face,could just be optimism and floating particle delusional vision. Any suggestions past what I’m doing here? Any suggestions on the cause or fix? I’ve searched everywhere on the web, don’t see this specific issue addressed.
Any assistance would be greatly appreciated!

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#25

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#26

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#27

I would first check out the roof, to make sure the water is not coming from the roof opposed to condensation. Do you have any pictures of the slope transition?. What pitch is the upper section? What underlayment is on the upper section?


#28

That looks like the result of Ice damming.


#29

Pictured is the upper slope, where it goes to vent is the face of the gambrel.
Doesn’t look like it is coming from the transition, unless “Ice damming” would make it move upward from that transition? I don’t know what Ice Damming is, going to look into that. Under the shingles , I believe the sticky Ice dam stuff, I know they installed the first few feet, near the gutter with that, not sure about the face/ upper transition…


#30

image
Great, this looks exactly how mine is set up. Maybe I just need to block off at the plate?
Found this here…


#31

Do you have ridge vent? If so what type? Any pictures from outside?


#32


Here’s the front, what you see in the pics is atbthe slope transition. The is a ridge vent all the way across the top peak. There is drip edge vent at the gutters both front and back. The back is shallow pitched, and shows no sign of any issue. //////// Adding to this,forum won’t allow more posts…///////////////////////////////////////////////////////////////////////…No drip edge at transition, only singled ridge there. Should I block off the vents at the top plate? I could batt insulate easily to close off. The PDFs attached and the pic that came from it shows that how it is set up is wrong, with air flowing from bottom edge of face all the way to ridge vent.??


#33

If you have eave vent, ridge vent, baffles even crushed ones, I can’t see that likely being condensation damage after 4 years but i could be wrong.

I would first take a good look at how the transition is shingled. I cannot tell from picture, are the shingles bent over the transition, Or is there a metal flashing?

We always run the lower slope up and stop at the transition. Then run the ice shield from the upper slope and turn it down 2" over the lower section. Install a metal flashing or drip edge, then install the upper shingles 1" over the flashing. Have seen laminated shingles fail if just bent over the transition.