I live and work in a part of northern California where we don’t quite have four seasons every year. Everyonce in a while it snows. We have hot summers, mild and wet springs and autumns.
My question about attic ventilation stems from the common practices of the builders in my area. I work for a GC as a draftsman and often call out the ventilation req’s for the houses that I draw for him and his customers.
What typically happens is bird blocks (vented eave blocks) get installed between trusses, every third bay, and a ridge vent or eyebrow vents at the peak. Crawl spaces are always vented and uninsulated.
The math I’ve done suggests that these attic vents are way out of balance, with typically 90% of the vented area at or near the peak. I have no idea what kind of effect this has on the temperature exchange or humidity inside the structures. We don’t worry about humidity here, though we are required to use vapor barriers on exterior walls.
Some codes, such as a reflective barrier under the roofing, are not enforced at all. Other codes are simply referrenced by the planning department, such as roof ventilation requirements but not strictly enforced by inspectors.
So in a dry/drier enviroment (I searched but could only find reference to humid environs) what is the ideal for unheated attic space? Most people out here are only concerned about the summer and controlling the heat of the attic space.
I have my ideas but would love to hear the voice of experience.
Replies
Greetings j,
This post, in response to your question, will bump the thread through the 'recent discussion' listing again.
Perhaps it will catch someones attention that can help you with advice.
Cheers
'Nemo me impune lacesset'
No one will provoke me with impunity
Jase
I'm not a builder, so I can't give you definitive advice. But I suggest that, for an introduction, go to http://www.hgtvpro.com/hpro/home. Click on "Best Practices", then on "Insulation & Venting". Select the video you want to watch. One particular video does address your concerns and, towards the end, explains why gable vents and power vents are inappropriate to insure adequate venting of an attic.
Hope this helps some. Perhaps someone with more knowledge will jump in and affirm or argue with the HGTVpro video's conclusions.
Good luck.