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I have a friend that has a cathedral ceiling over part of his house. The examination I have done shows no ventilation for this part of the roof. He is contemplating reroofing his home and I am curious if some sort of vents should be added.
This section would simply have sheetrock, fiberglass insulation, roof sheathing, paper, and 3-tabs. If some type of ridge vent is added, will there be any air space to pull air through? From where? Do eave vents need to be added also? What if the cavity is literally full with fiberglass? Is it good to try and vent it anyhow?
I am assuming the main drawback to the current situation is that the roofing, 3-tabs, will wear out much faster because they essentially overheat, is this correct? Any and all information will be appreciated.
Thanks- Tim
Replies
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Tim, it isn't gonna make a weeks difference to the shingle life (my opinion) but it will affect the warranty. Venting the roof will require less insulation and obviously you will need to vent the eave, where else is your air going to come from?
Questions: is the entire roof being replaced? Is it all the same age? Are some areas vented? Do those shingles show less age than the ones on the unvented cathedral area? Does he/do you think the shingles need replacing because the roof wasn't vented?
If anybody bothers to reply this will turn into a food fight, but you can find tons of info on this subject in the archives. It's been fought before, not sure any one was convinced to change their opinion though. Joe H
*Thanks, Joe, for your input.No, the shingles all look the same- cathedral and attic alike. Yes, the whole roof will probably be replaced. It is about 15 years old and looking long in tooth. Some tabs have blown off, etc.So, if it were your home, would you go to all the trouble to add the ridge and eave vents, or just forget it?Thanks- Tim
*I would at least add the ridge vent since you still get alot of heat in the peak of the vaulted ceiling. They are easy to install and would relieve at least some of the hot air trapped in there. Just a thought, Dave
*I'm pro-vent....but this is one case where I'm pro-seal! Just had this discussion with a buddy. The home inspector said to add a ridge vent. To me...a ridge vent w/o soffit is just a hole in the roof. My advice to him......get up there...super insulate....and seal off the entire attic from the heat/AC envelope. Seems to me a one or another situation. Jeff
*Jeff has my vote on this one.It doesn't make sence to penetrate the roof so you can have a vent that doesn't work.Vince
*What area of the country is he in? Does he have any signs of ice damming with snow on that part of the roof?
*I think Tim answered his own question.A 15 year old roof and the shingles have all aged the same. The vented areas and the un-vented areas are in the same condition.I don't see how adding an un-functioning ridge vent will do anything besides add a potential leak----and I question weather adding soffit vents at this point will allow the rv to function given the clogged rafter bays.
*Hi, Bill,No, he lives in the southwest in a city where some winters they don't even get snow. So, ice damming is no problem.Thanks= Tim
*One of the reasons for venting a cathedral ceiling is to prevent the buildup of warm, moist air that may have migrated up through the insulation (eg. through recessed can light fixtures) and will condense on the underside of the sheathing in cold weather. Here in the midwest I've had good results with an approach I first heard about from moisture control guru, Henri DeMarne in Vermont. He recommends stripping the old roofing off, applying panels of at least 1" isocyanurate foam insulation over the sheathing, running 1x sleepers directly on top of each roof rafter from eave to ridge, and finishing with a second layer of plywood sheathing, #15 felt and 3-tab shingles. A continuous ridge vent at the peak and vertical spacer blocks behind a second fascia board will allow for continuous air flow under the roof surface in hot weather and cold. This approach realy works! Good luck.
*There is an other material that will work as Ted outlines. I forget the trade name, but essentially it comes in 4x8 sheets and is a little over an inch thick. The top surface is a nailbase like 7/16 osb and the bottom surface is kind of a perforated waffle looking foam board. I have never had call to use it,but I have seen samples several times.
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I have a friend that has a cathedral ceiling over part of his house. The examination I have done shows no ventilation for this part of the roof. He is contemplating reroofing his home and I am curious if some sort of vents should be added.
This section would simply have sheetrock, fiberglass insulation, roof sheathing, paper, and 3-tabs. If some type of ridge vent is added, will there be any air space to pull air through? From where? Do eave vents need to be added also? What if the cavity is literally full with fiberglass? Is it good to try and vent it anyhow?
I am assuming the main drawback to the current situation is that the roofing, 3-tabs, will wear out much faster because they essentially overheat, is this correct? Any and all information will be appreciated.
Thanks- Tim