Ventilation required?

[Michael R. Boyett]

Scenario: Two story home, two car garage, front 1/2 of garage has attic space above it that is not shared with anything else...just 200 sf or so of dead space. Attic wall on back side that is shared with livable space is insulated. There's soffit vents on two sides but no gable vent, ridge vent or other passive venting up high to discharge the hot air. Is there a requirement for ventilating that size & type of attic space? The IRC seems to be silent on it. I'm sure many of us would recommend it but is there any requirement?

[Jeffrey R. Pope]

Generally, the attic space above a garage does not require ventilation.

[Michael R. Boyett]

Originally Posted by jpope

Generally, the attic space above a garage does not require ventilation.

Jeff...is that a personal opinion or can it be backed up anywhere? I thought there was a size, i.e a square footage minimum, but I can't find it anywhere. This is just for my own and another inspector's curiosity and future reference.

[Jeffrey R. Pope]

Opinion based on experience and research in the UBC. I can't say whether this also applies to the IRC.

The UBC classifies a garage (attached or detached) as a Type U Occupancy. Basically, the UBC defines a Type U Occupancy as a "utility" type room/space, which includes garages and other "non-living" spaces.

I have never seen attic-ventilation requirements that apply to Type U Occupancies.

[Michael R. Boyett]

OK, good deal...I'll drill down some on the UBC and IBC.

[James F. McKee]

that still doesn't address the excessive shingle wear and curl in the un-vented space...imho....

[Michael R. Boyett]

Yes, I agree..the inspector that had originally asked my opinion on this noted exactly that on his report today. There's definitely reasons to add ventilation but I was/am hoping for something tangible that a builder can relate to. As I investigate the IBC I see and agree with Jeff....maybe. One section, 1203.2, of the 2003 IBC that is not Occupancy specific says that ventilation is required. So, I don't have the final answer from a code standpoint just yet.

[David P. Valley]

I like all roof cavities to be vented, but if the attic is not insulated (such as...above a garage) I don't make a big deal out of it. It's the insulation application that will cause attic cavities to become ovens.

IBC-2003 & 2006 Section 1203 - Ventilation

1203.2 Attic spaces. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof framing members shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain and snow.

Blocking and bridging shall be arranged so as not to interfere with the movement of air. A minimum of 1 inch (25 mm) of airspace shall be provided between the insulation and the roof sheathing. The net free ventilating area shall not be loss than 1/150 of the area of the space ventilated, with 50 percent of the required ventilating area provided by ventilators located in the upper portion of the space to be ventilated at least 3 feet (914 mm) above eave or cornice vents with the balance of the required ventilation provided by eave or cornice vents.

http://www.southface.org/web/resourc...lings_4pdf.pdf

[James F. McKee]

sorry Mike i'm not a code inspector ...just use my experience in construction since 1968

[Richard A. Hetzel]

Yes, I agree..the inspector that had originally asked my opinion on this noted exactly that on his report today. There's definitely reasons to add ventilation but I was/am hoping for something tangible that a builder can relate to.

There is such a thing, and it's called "good practice"! A building code, as many have said here, is only a minimum standard, and not necessarily a primer of good practice. One should not need a code to realize that any enclosed wood structure needs ventilation. However, ventilation is more art than science, and perhaps the soffit vents are enough, or perhaps there is a ventilation path to a ridge vent above the insulated space.

[Jeffery L. Haynes]

From a practical standpoint it should be vented......if for no other reason because of the heat that builds up from underneath which in turn will diminish the service life of the shingles.

Amazes me why a builder would spend an extra $600.00 on architectural shingles yet save $40.00 by not adding ridge vent over the garage......what a moron.

What alarms me is where the right slope of the garage roof dumps into vertical wall over the foyer.................amazes me why architects design homes to fail.

Is this a vinyl sided home with a brick veneer on the front.

regards

Jeff

[Bruce M. Graham, III]

code is the minimum, the shingle manufacture will want to see ventalation or there will be no warranty, not that it is easy to work through a roofing warranty.

[Michael R. Boyett]

Originally Posted by jhaynes

Is this a vinyl sided home with a brick veneer on the front.

No, not exactly. This is a Hardie sided home with a brick veneer on three sides.

[Michael R. Boyett]

Originally Posted by bgraham

....the shingle manufacture will want to see ventalation or there will be no warranty....

Now, there's an interesting angle. Owens-Corning literature states "Regardless of the deck used, the roofing installer must ensure that the attic ventilation meets or exceeds FHA Minimum Property Standards." Now, if I knew what that standard stated...

[Joe Funderburk, CMI]

Originally Posted by jhaynes

From a practical standpoint it should be vented......if for no other reason because of the heat that builds up from underneath which in turn will diminish the service life of the shingles.

Agreed. And the garage will be a sauna. The IRC doesn't distinguish between attic types to my knowledge. Venting is required per the IRC. I write it up recommending ventilation when I see it.