this free document is 74 pages for your climate at:
http://www.buildingscience.com/desig...MixedHumid.pdf

JA wrote:
What are the pros and cons for using ridge vents? I'm having my house
re-shingled, and got estimates from two highly recommended roofers. One
recommended installing a ridge vent; the other did not. The one who did not
recommend a ridge vent re-roofed our other house last year and insisted on
installing a ridge vent.

The house we're re-roofing is a two story "colonial" with an unfinished
attic that has both soffit vents and gable vents. The house we re-roofed
last year is a bungalow with the second floor (what would normally be the
attic) finished.

I will discuss this with each of the roofers before I decide which one to
hire, but I would appreciate any insight anyone can give me.

Also, are there any shingles that really resist algae stains, which seem to
be a big problem in my area (Maryland)? Both roofers want to use
Certainteed XT25AR, and neither seemed enthusiastic about the more expensive
"architectual" shingles, although both were willing to install them if
that's what I want.