Eave ventilation n ot required in current CRC/IRC?

[Rio]

We have a project where we have to provide fire resistant vents which we can do but looking at the 2010 CRC code (based on the 2009 IRC), Section R806.2, it appears that as long as we provide 1 s.f./ 150 s.f. of attic space we can omit the eave vents. This will make things easier for construction as we won't have to provide baffles to keep the air flow area open and we won't have to be concerned about the bird blocks reducing the shear transference from the roof diaphragm to the wall plan. It does mention in Section R806.3 that " where eave or cornice vents are installed, etc." which reinforces my belief that they are not required.

As I understood it, under the 2007 CBC (based on the IBC) there was no option to the requirement that 50% of the attic ventilation had to be along the eaves or cornices so I am concerned that I might be missing something in reading the code section(s).

The project is located in southern California, close to the coast, so ice dams are not an issue.

Any insight on this issue would be appreciated,

Rio

 

[mark handler]

ventilation while trapping flames and embers

http://www.brandguardvents.com/

California State Fire Marshal approved

 

[conarb]

Rio:

That code section has had me scratching my head too, in my current job fire-dampened soffit vents are costing me over $6,000 (and this doesn't count ridge vents buried in my roofing bid), but I want and need them for the ventilation. This issue does need clarification.

 

[mark handler]

The goal in attic ventilation is High/low and cross ventilation. If you do not provide low vents, the air will just go from one upper vent to another upper vent.

If you do not provide proper venting you increase the heating and cooling costs, and it will decrease the life of your roof.

 

[pyrguy]

Remember, what code allows is not necessarily the best thing. Code does allow for for the deletion of the eve vents. Is it smart?

Unless the attic is inside the building envelope, I would want all the eve and attic vent square inch openings I can get.

 

[Rio]

Thanks for the feedback everyone. We do call out for brandguard vents when dealing with projects in the W.U.I. (Wildland Urban Interface) and the comments regarding what is allowed versus what is right are valid ones. We talked with the plan checker and he's okay with us omitting the eave vents, it's in a temperate part of San Diego County and the roof will have light colored concrete tiles so I'm not concerned about the roof holding up with less cross ventilation, we'll be able to get the insulation in better without having to deal with the baffles, it will cost less and in this case it's more practical so that's the way we're going, no eave vents, just two nice big brandguard dormer vents.

 

[conarb]

Rio:

I think adequate, even more than adequate ventilation is more important than bulk insulation, in my case I'm using the more expensive high density R-38 "Cathedral Ceiling" insulation to maintain my Title 24 R-30 requirement while increasing my air flow space from 1½" to 3½", I could stay at 1½" and go to R-38 with the high density but prefer the larger air-flow. In a very cold climate more bulk insulation makes sense, but in your San Diego or my Bay Area climate I don't see bulk insulation as doing much good. Over the years I've removed bulk insulation when remodeling where the insulation was asbestos or not fireproof, and the owners reported no difference in their utility bills.

 

[mark handler]

It is estimated that 9 out of 10 homes in North America do not have proper attic ventilation.

Types of damage that can result include:

Premature aging of your roofing system (“fried” shingles)

Warping, cracking, or breaking down of wood framing

Damage to siding, exterior or interior paint, and wallpaper

Higher energy costs

Roof deck warping and rotting of the wood frame

Mildew growth

Buckling of shingles and felt

http://www.gaf.com/Roofing/Residential/Products/Roof-Vents/Attic-Vents-Roof-Ventilation.aspx

 

[mark handler]

You may find that your roofing warranty and Home owners insurance can be effected if you do not provide code required ventilation