Venting a Hip Roof??

10530 Views 7 Replies 4 Participants Last post by Ed the Roofer, Apr 6, 2009

CrossWorks

Discussion Starter · Apr 3, 2009 (Edited)

I wanted to create this topic because I have someone inquiring about proper venting of a Hip Roof. It appears her contractor has neglected to install rafter vents in the bays which "die-into" the hip rafter. As a remodeler, it has always been my practice to drill a 1-1/2" hole 1" down from the top of the roof rafter and 6-8 inches back of the hip rafter, and when installing the rafter vents I make sure that air flow will capture that hole, then install the insulation making sure there is no blockage.

Being in Maine, in the late fall when frost comes around, you can always tell if a roof has been properly vented (and or insulated) when you see some bays with frost and some without. Those without frost in my opinion means a neglect to do what I indicated above and is evident of heat loss.

So with that said. Can anyone confirm or refute my approach to properly venting Hip Roofs??

Thanks

See an example here>>>>>>>CrossWorks Carpentry

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Ed the Roofer

· #2 · Apr 3, 2009

I have done it, although certain vent manufacturers, such as Air Vent state that it should not be done, but Mid-Master and Owens Corning will allow it per their specifications.

But, I do believe in the Air Vent theory.

The times that I did vent the entire Hip length of the roofs, was when their was a vaulted/cathedral ceiling over that section of the home and I also included 100% continuous new Intake Ventilation to vent each rafter bay and notched each jack-rafter to create a cross ventilation flowage.

Ed

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CrossWorks

Discussion Starter · #3 · Apr 4, 2009

Thanks Ed,

Good to know. I am surprised I didn't get more input from the rest of the viewers. To me the whole process makes sense and I'm not sure why it would not be recommended by manufacturer's? For them to suggest otherwise only leaves me somewhat baffled. I mean, if your going to vent a roof, why is it okay to disregard 40% of the roof on let's say a 40 x 50 structure with a hip roof?? Anyway, I''m hoping I can get some more input from other contractors regarding this issue.

Thanks for yours! :thumbsup:

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adelaide11

· #4 · Apr 4, 2009

Well it seems to me that you are quite good in your job and applying all kind of tricks so that your work can give better results.

Will you please tell us what will be the price of your work, so that we can delegate some extra work to you.

___________________
roofing contractors | roof repairs | roof replacement

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Teach88

· #5 · Apr 4, 2009

hip roof help

I just started having my attic remodeled for a bedroom/storage/office space. I would be very appreciative if anyone could answer any of these questions..
I have a 100 yr + house with a hip roof, with only soffit vents..from what I can gather. There is a roof overhang..and when it was sided they put these vinyl covers with holes in them up against that overhang? Thats what it looks like from outside.
I would like to ask opinions about any of the below, because I have seen damages done when roofing is ruined; my friend's entire attic bedroom is moldy and water damaged because hers wasn't vented. I dont want this to go to far without being sure it is right:

1. What kind of vents do I need? He put the 'proper vents' styrofoam and r21 in the main section. just the rolled stuff in the hip areas and dormers. He isn't planning any vents, although the proposal says 'vents' . I wonder what kinds of vents I need? He says the natural flow of air from the soffits accross the large open square area at the top will be enough. I wonder about that 40% in the hips areas not being vented.

2. Should plastic vapor barrier be put over the insulation? I have seen this done on TV. and they put sheet plastic over it. He says I dont need it.
3. I plan to heat the area in winter with electric baseboard and cool with window airconditioner located in a window dormer. Will this be enough?

4. One hip area will be an office nook one dormer east side will be a open work space for sewing etc. the other two hip areas ( south side) walled off with doors for closet/storage. Should the enclosed closets be vented differently? These are on the south side of the house and the only area that get large icecycles, so I am worried about something being wrong there.
5. For the knee walls, he insulated down the main roof, and does not plan to insulate the knee walls themselves. He says they dont need it, if the ceiling line is insulated. Is this correct? Anyone have any idea of the best height for kneewalls? I thought 42 at most because they eat into the main living area too much.

I dont know what else you need to answer except may that the house is in upstate NY, and had blown in fiberglass done in house walls and attic floor 10 yrs ago. The attic floor was done as it wasn't a living space then. I dont think it did much as the house is cold and drafty.

I know I asked a lot of questions but any help at all is greatly appeciated.

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Ed the Roofer

· #6 · Apr 5, 2009

A proper Vapor Barrier needs to be installed Under the insulation in the attic or in the individual rafter bays of a vaulted/cathedral ceiling and also continuous balanced air flow, created by sufficient Intake and Exhaust Ventilation.

If this is a vaulted/cathedral ceiling, then each of the jack-rafters that dead end into the hip rafters need special work done to them.

Either the drilling of the holes as suggested by the OP, or the notching out of the equivalent air spaces from the top of the hip rafters, or the installation of a product that gets installed on top of the hip rafters, called Rafter Vent. manufactured by DCI Products Inc.

Ed

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Teach88

· #7 · Apr 5, 2009

Thanks Ed for the response.

I looked up the rafter vents. They discuss them being added on top of the plywood in new constuction. So, at this point with a remodel of an old house attic,that doesn't seem possible...........so, am I to understand thatin the hip areas we need to make those holes? What is the risk if it is not handled that way? I dont think he added the styrofoam under the insulation, so should it be taken down and redone?

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Ed the Roofer

· #8 · Apr 6, 2009

The Rafter Vents from DCI Products go Under the plywood to create a cross current of air flow.

If there is No air space on top of the insulation, then yes, the decking should come off and then have the insulation baffle vents installed.

Ed

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