Ventilation - addition - new roof tied into existing roof

I have a 12’x44’ Park Model with cathedral ceilings throughout. Roof is 4/12 pitch. I am in the process of adding a 12’x12’ addition off of the living room area. The addition section will not have a cathedral ceiling. The new addition roof will tie into the existing park model roof. I plan on stripping off a section of shingles on the park model, then adding valley nailer boards on top of the existing plywood sheeting for my rafters, then framing the new roof over top of the existing roof.

My question is: Because the soffits on one side of the existing roof will be blocked by the ceiling joist of the new addition, will I have a ventilation problem in the cathedral ceiling section of the park model roof?

Ok, i have a few questions before i can answer your question. First off is this a mobile home? the name you call it has me wondering. To try and answer it without answers, you will have to keep the attic space open to the existing to the new. with the ceilings you have it is vital for proper airflow. Going right over the existing roof will cause problems. You will need to keep it open for intake to pass thru. Or you will have hot spots.

To gtp1003:

Thanks for the reply - I was hoping that I did not have to cut out part of the existing roof sheating but it appears based on your answer that I have no choice but to do so. Again, thanks for the help.

PS - Yes, a park model is similar to a mobile home, but are usually smaller. Park models are usually found in campgrounds. The wheels are usually removed and the unit is set up on pillars - foundations are not allowed.

gtp, could he use Smartvents on that individual section I’m thinking? And wherever else it is blocked? I’ve been meaning to call Certainteed and ask them what they think of Smartvent. How much luck are people in the north having with Smartvent? I learned of the Smartvent here on this site somewhere of it, then I found them and called the company and had them send some information and a sample and I saw a lot of possibilities for some old venting problems. Damn, that sounded like a commercial. It’s the situation I would try taking the time to learn about, though.

It might but im old school. Looking at that vent i really dont have alot of faith in them. With ice in the smart vent area i really worry about ice in the vent also when it does ice up and it will its just the way it is it blocks the airway. Even if snow is on the roof it will block the intake and thats a bad thing. Then it will ice up and your back to square one. In warmer climates it probably works great but when 8 inches of snow is sitting on the roof the vent is useless. The exhauist will clear itself but the intake can not. Since this is a home with cathedral ceilings i would be more inclined to go the standard route with a few baffles to insure the proper ventilation. But i understand where you are comming from. It might work but i can not help my customers with mights and it shoulds. It is just the way that i am.


You need less of an air flow in the winter to exhust thru the ridge vent.

You will get enough air through the sides.

I dont understand what you are saying? If you are saying that you need less airflow in the winter then i will have to disagree with you on that. If this is the case please explain why you need less airflow in the winter. Penn where in the country is this located so we ccan define the needs a little clearer.