# Garage Vents



## conarb (Nov 26, 2012)

Under the IRC are vents still required in unconditioned garages?  We've always put foundation vents in the garage walls or even doors to allow car exhaust fumes out, but I can't seem to find the requirement in the IRC (actually the CRC).


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## Daddy-0- (Nov 26, 2012)

Not required conarb


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## fatboy (Nov 26, 2012)

Agree, not a requirement in the IRC, can't speak to the CRC........


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## brudgers (Nov 27, 2012)

conarb said:
			
		

> Under the IRC are vents still required in unconditioned garages?  We've always put foundation vents in the garage walls or even doors to allow car exhaust fumes out, but I can't seem to find the requirement in the IRC (actually the CRC).


  Carbon monoxide has an atomic weight of 28.   This is less than that of Oxygen, 32.

  It is equal to that of Nitrogen, the primary component of air.

  Nitrogen and Oxygen make up 99% of what we call air.

  In otherwords, Carbon monoxide is lighter than air in general, and neutrally buoyant relative to its primary component, Nitrogen.

  So Carbon monoxide will tend to rise to the top of an enclosed space, not fall.

  Given that exhaust fumes are hot, convection alone would carry it upward.

  Putting vents at the bottom is the worst ventilation strategy when it comes to carbon monoxide because it is contrary to basic science.

  I'm the ICC is considering mandating them.


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## mtlogcabin (Nov 27, 2012)

Did CA include the mechanical portion of the IRC when adopted? or are you using the UMC?


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## Alias (Nov 27, 2012)

mtlogcabin said:
			
		

> Did CA include the mechanical portion of the IRC when adopted? or are you using the UMC?


CA uses the UMC & UPC as the basis for its' CMC & CPC.

Sue


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## mtlogcabin (Nov 27, 2012)

Then Table 4-4 could apply if the parking garage is over 1,000 sq ft and used for the storage of 5 motorized vehicles. See footnote 7

The only reason I mentioned it is I know Conarb builds some larger homes which may have some large garages in them

We only use the first 11 chapters of the IRC so we have to use the IMC for one and two family dwellings and the IMC Section 404 requires ventilation of a parking garage. It can get confusing when parts of a code are adopted or a mixed from different code families


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## tmurray (Nov 27, 2012)

brudgers said:
			
		

> Carbon monoxide has an atomic weight of 28.   This is less than that of Oxygen, 32.
> 
> It is equal to that of Nitrogen, the primary component of air.
> 
> ...


specific gravity of oxygen 1.14

specific gravity of Carbon monoxide 1.0

...it floats!


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## tmurray (Nov 27, 2012)

tmurray said:
			
		

> specific gravity of *air* 1.14specific gravity of Carbon monoxide 1.0
> 
> ...it floats!


oops...fixed


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## Sifu (Nov 27, 2012)

I asked ICC for a technical opinion concerning a dropped ceiling in a residential garage not too long ago.  I was concerned about the passage of CO from the garage to the space above so I wondered if the rated ceiling assemblies were condidered to be or in fact required to be atmospherically sealed to prevent the passage of gases.  The answer was NO (no rating for passage of gas, although I'm not sure it is all that different than smoke, and no requirement).  The ceilings must only be sealed to prevent the passage of products of combustion.  So I guess they aren't worried about the CO rising.


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