Attic ventilation question

[Peter Doane]

General question, for you expert roofers. I dont have pictures or anything but here goes.... If the interior is a vaulted ceiling (no attic space other then between the rafters) Should or shouldnt there be roof or ridge vents. I find 50% of the time there are soffit vents and no roof vents on vaulted ceiling constructions. Some with roof vents, some without roof vents but all have soffit vents??? Is there something Im missing. Concern or not a concern?

[Emmanuel J. Scanlan]

Peter,

Will do you one better and provide a very good reference source for your "Favorites" folder. The people at Air Vent are also happy to answer inspectors questions.

http://www.airvent.com/professional/...terature.shtml

[Barry Adair]

Great question!
Depends on when/where it was built and AHJ.

Down here old school of thought was under size the rafters, usually 2x6. 24"OC, 1/2" ply deck, over vaulted area, and seal the insulation in the cavity, usually R-13. Some serious deflection occurs and you don't ever what to open one of these up. Nasty stuff is usually dwelling in the rafter bays.

Now I'm seeing soffit vents, insulation baffles, ridge vents...unless they are the newer technology conditioned attic space, completely sealed system.
http://www.buildingscience.com/desig...es/houston.pdf

Manny,

Great site info!

[Peter Doane]

Thanks for your links to the sites guys. Berry, Im talking about newer homes, 2000 to 2006. Hard to tell if its a "sealed" system, unless thats why the knee walls in the loft space are sheetrocked???

[John Onofrey]

Originally Posted by badair

Great question!
Depends on when/where it was built and AHJ.

When I do attic ventilation inspections in Houston, Texas I expect to see baffels in each rafter bay leading from a lower vent to an upper vent. Top 2 Bottom.

Most of the attic ventilation systems here are installed incorrectly with regards to vaulted ceilings. Insulation contractors install the baffels and usually do a miserable job. In my opinion, the same contractors that install the upper and lower vents should install the rafter bay vents. Insulation contractors usually install 50% of the material either due to laziness or cost cutting.

http://www.adoproducts.com/duro.html#1

[Adam J. Slimack]

What good are 'inlet' vents without 'outlet' vents? (Not much) Kinda like trying to blow into a glass. You're not going to get air in if there if there is nowhere for the air in the glass to displace to.

[David P. Valley]

Attachment 5287
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[Barry Adair]

ASHRAE JOURNAL

http://www.fpl.fs.fed.us/documnts/pd...c%20venting%22

[Barry Adair]

ASHRAE JOURNAL

http://www.fpl.fs.fed.us/documnts/pd...c%20venting%22