There are lots of ways to insulate a low slope roof and most of them are wrong.
Low slope roof ventilation problems.
When it comes to low slope roof systems the old adage that an ounce of prevention is worth a pound of cure truly applies.
Resilient synthetic rubber membrane widely used on low slope roofing projects for over 50 years in the united states and worldwide.
The problem with that was that with the slope as low as it was the doubled up drip edge made for enough of a ridge that the shingles sloped back a little forming a trough for water to accumulate in.
Some of the most common low slope roof problems relate to improper installation or lack of maintenance.
These vents can be located in the soffits in gable walls in the roof surface or at several of these locations but should be distributed so as to provide effective cross ventilation.
So two segments were installed overlapping by 6.
For ventilation channels to be effective you need a slope of at least 3 12 or steeper.
A lot of roofing contractors in the area could just provide you with a band aid solution using mostly a caulking mixture to cover up the leaks and this will certainly not last long.
Flat and low slope roof designs to avoid moisture condensation problems flat roofs call up a whole new breed of building moisture problems how to avoid moisture traps under flat roofs avoid mold rot caused by moisture trapped under un vented flat roofs questions answers about the cause cure prevention of moisture problems in flat roofs and similarly hard to ventilate structures.
Secondly you really have two different roof types working here low slope or flat roofs and pitched roofs.
Low slope roofs are difficult to ventilate but there are a few techniques that work.
For flat roofs or low sloped roofs with pitches of less than 1 6 such as cathedral ceilings the total net vent area should be at least twice as large or 1.
Basically you need lots of height above the top of your insulation layer plus a few vented doghouses cupolas.
Using v2t vents the vent secured system creates a suction effect that strengthens the entire roof and holds the membrane securely in place.
Unfortunately too many builders and roofers do not include any ventilation on a low slope roof as it is easier for them to avoid potential leaks.
Since low slope roofs are more susceptible to leaks the key to making your low slope roof to function well is to increase the waterproofing properties of your roofing system.
In the case of low slope roofs builders and roofers not only need to solve the ventilation problems but they also have to make sure that there are no leaks caused by the air vents.
I have seen ventilated flat roofs but they are usually used in conjunction with attic spaces and you mentioned finished vaulted ceilings in your post.
Updated on april 8 2016.