what effect does changing the pitch of a roof have on the insulation properties and durability of a roof?
The pitch of a roof has zero effect on the r-rating of insulation. Proper ventilation of the attic space, whether steep or low pitched, simply provides the optimum environment for the r-factor of the insulation to do its job more efficiently. Any attic, regardless of pitch, if it is not properly ventilated, would stress the effectiveness of any insulation product unnecessarily. The durability of the roof is not adversely affected either.
I'd have to agree with mj, your insulation in your ceiling is the major factor for heating and cooling , spec R-38 but if your going for gov. kick backs I think it's R-41 (17" of blown in fiberglass insulation). Roof pitch standard is 1' raise to 4' run, (really easy to re-roof & inexpencive). Advantages of a steep roof (less apt to have leakage problems with a worn roof, you get a few more yrs). When you have to replace that roof, price goes up for steepage.
Increasing the pitch will of course result in a larger dead air space therefore more insulation. The greater pitch is also less likely to leak but of course more costly to construct as more material is needed. Install vents at the peaks for more efficiency. Shingles will be less likely to be lifted by high winds with the steeper roof also.
As long as the insulation in the attic area is not changed then the insulating value should not change. As far as durability concerning the pitch of a roof it realy depends on the type of shingle you use.
by raising the pitch the attic will stay in the cooler in the summer. also the steeper the roof the less wear you will have on certain types of roofing. wood, metal , and tile like steep roofs. mineral roofs dont, since the grainuals on the tar rub off easily during rains and snow will stick to the mineral surface and rip off the grainuals on the steeper roofs. a good pitch is a 6 and 12 pitch. this works well with all roofs and gives good cooling plus you can still stand on it to door any work
