# IBC 2009 1203.4 Natural ventilation



## pmarx (Jan 20, 2012)

Can someone please confirm (or deny) that "minimum openable area" (1203.4.1) is the clear area a window will provide in the open postion similar to an emergency escape window (1029.1) which at least uses the words "clear opening"? Thanks.


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## mark handler (Jan 20, 2012)

1203.4.1 Is for light and ventilation

1029.1 Is for egress

Unrelated

Similar but not the same

1203.4.1 can include window trim/stop

1029.1 can not


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## pmarx (Jan 20, 2012)

Thank you Mark. I realize that the two sections address different issues, I was using the latter for it's specific terminology. "Openable area" is too ambiguous for me to use anything less than the figures I arrived at using the formula the Traco engineer gave me. Maybe that's a worse case than including trims and stops but I'd rather err on the side of caution.


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## gbhammer (Jan 20, 2012)

The 2009 commentary 1203.4 has a diagram that mentions the glazed area for determining openable area for ventilation.


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## pmarx (Jan 20, 2012)

gbhammer said:
			
		

> The 2009 commentary 1203.4 has a diagram that mentions the glazed area for determining openable area for ventilation.


Thanks. I can't say I agree with your conclusion about Fig. 1203.4.1 but I asked an associate to fax that page to me and in the commentary it states, "openable area (the net-free area of a door, window, louver, vent or skylight etc., when fully opened."

I still say the code is ambiguous but not including "net-free" as it does in the emergency egress window section.


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## pmarx (Jan 20, 2012)

OK, technically the emergency egress window section states "net-clear".


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## gbhammer (Jan 20, 2012)

I would use the net free area.


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## imhotep (Jan 20, 2012)

pmarx said:
			
		

> Can someone please confirm (or deny) that "minimum openable area" (1203.4.1) is the clear area a window will provide in the open postion similar to an emergency escape window (1029.1) which at least uses the words "clear opening"? Thanks.


What is the calculation?

Assume a 10 x 12 room = 120 SF x .04 SF/SF = 4.8 SF required

What size window is proposed?  Does it really come down to opening size versus frame size?


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## pmarx (Jan 20, 2012)

Most of the spaces are below 120 SF so the proposed windows exceed the 4% minimum requirement. The window unit is a 40"x61" aluminum slider. Per the manufacturer, the formula for the vent area is W/2 - 5-1/4”x H - 6-5/8”. I come up with 5.6 SF. This is fine except for one particular bedroom that is 170 SF (6.8 SF). I’m just trying to justify to the project architect the need to revise some windows.


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## mtlogcabin (Jan 20, 2012)

> I’m just trying to justify to the project architect the need to revise some windows.


Or provide the documentation that it meets the mechanical ventilation requirements. Remember  they have to meet natural or mechanical but not both.


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## imhotep (Jan 20, 2012)

pmarx said:
			
		

> Most of the spaces are below 120 SF so the proposed windows exceed the 4% minimum requirement. The window unit is a 40"x61" aluminum slider. Per the manufacturer, the formula for the vent area is W/2 - 5-1/4”x H - 6-5/8”. I come up with 5.6 SF. This is fine except for one particular bedroom that is 170 SF (6.8 SF). I’m just trying to justify to the project architect the need to revise some windows.


Ask the architect for the proposed/required calculations on the questionable window and let him figure out a change is needed.


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## pmarx (Jan 20, 2012)

I work for the architect. LOL, trust me, if I was the plan reviewer I wouldn't have done the calcs in the first place.


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## imhotep (Jan 20, 2012)

pmarx said:
			
		

> I work for the architect. LOL, trust me, if I was the plan reviewer I wouldn't have done the calcs in the first place.


Funny that.


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## Architect1281 (Jan 20, 2012)

When reviewing net natural vent are i use the glass area and use a reduction factor for screening then let the designer argue back and yes I do check the submissions

get alot of these as most college dorm / frat / apartment designers dont figure it right until we meet, then they get the next one right. Some use combined baths lavs etc as mechanical and live / sleep as natural - thats always fun


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## pmarx (Jan 21, 2012)

Architect1281 said:
			
		

> When reviewing net natural vent are i use the glass area and use a reduction factor for screening then let the designer argue back and yes I do check the submissionsget alot of these as most college dorm / frat / apartment designers dont figure it right until we meet, then they get the next one right. Some use combined baths lavs etc as mechanical and live / sleep as natural - thats always fun


That's exactly what we're dealing with and the thing is that after they get their CO these windows will ever comply because they will put stops to limit the opening to 12" in width. The window height would have to be almost floor to ceiling and that ain't happening. This project is based on an earlier design that the owner wanted to repeat and the same thing was done there so...*shrug*


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## Architect1281 (Jan 21, 2012)

LImited Stops Limited Ventilation = More vent units


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## peach (Jan 22, 2012)

when did we take mechanical ventilation out?  The other issue is the window limiters if the window is >72" above grade and <24" above finished floor.  Even if those windows CAN be opened more than a 4" opening, they can't.


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## pmarx (Jan 26, 2012)

peach said:
			
		

> when did we take mechanical ventilation out?  The other issue is the window limiters if the window is >72" above grade and <24" above finished floor.  Even if those windows CAN be opened more than a 4" opening, they can't.


Sorry, I didn't follow the point about if the window is greater than 72" above grade plan and less than 24" AFF (the sill?). Is there a code section that requires opening stops? I know the code generally exempts emergency rescue windows below the 4th floor but that means it requires them (with exceptions) from the 3rd floor down. Those 3rd floor windows _will_ be greater than 72" above grade and will have to open to a clear size of 5.7 SF.

I also dispute that the architect has to design to the worst case of what a property owner may do after they get a CO. If those windows are installed as they came from the factory, namely they can be fully open to provide enough ventillation, that's all the architect should be responsible for. So unless someone can correct my ignorance of a requirement for limiting stops I think we're going with the windows as designed.


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## Yankee (Jan 26, 2012)

pmarx said:
			
		

> Sorry, I didn't follow the point about if the window is greater than 72" above grade plan and less than 24" AFF (the sill?). Is there a code section that requires opening stops? I know the code generally exempts emergency rescue windows below the 4th floor but that means it requires them (with exceptions) from the 3rd floor down. Those 3rd floor windows _will_ be greater than 72" above grade and will have to open to a clear size of 5.7 SF.I also dispute that the architect has to design to the worst case of what a property owner may do after they get a CO. If those windows are installed as they came from the factory, namely they can be fully open to provide enough ventillation, that's all the architect should be responsible for. So unless someone can correct my ignorance of a requirement for limiting stops I think we're going with the windows as designed.


yes, see 612.2


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## Big Mac (Jan 26, 2012)

If these are dorms rooms then I assume you are designing from the IBC, not the IRC.  The appropriate code section for the window openings at 72" or more above grade is Section 1413.2.


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## Architect1281 (Jan 26, 2012)

So the window at the bottom is limited in travel but the top can move dow or set the sill at 24-1/8" above finish floor rules are written to be avoided


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## Architect1281 (Jan 26, 2012)

I really mis the edit button - As a designer I NEVER let the building official dictate the worst Higest most deadly use that could happen. The owner states the intended use and the it is an enforcement / compliance issue. otherwise all uses would be H - now as a CBO thats what I assume when the applicant says use to be determined.


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## pmarx (Jan 27, 2012)

Big Mac said:
			
		

> If these are dorms rooms then I assume you are designing from the IBC, not the IRC.  The appropriate code section for the window openings at 72" or more above grade is Section 1413.2.


Thanks for the citation (but I had to hunt around chapter 14 because it only goes up to 1408). 1405.13.2 answers my question but still doesn't apply in this case as the sills are greater than 24" AFF but I'll be sure to keep this in mind.


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