Natural Ventilation and figuring openable area

[findingarch]

I'm looking at section 1202.5 Natural Ventilation in the IBC - is there any guidance for how to calculate that openable area when looking at vent-type windows...so casements, awnings? The question came up with regard to limit stops on the operable windows and what implication that might have on the natural ventilation requirements. So loosely if you have a 4'x5' window and half of it is an operable casement then regardless of limiters you have 10sf of openable area? Or do you look at the top and bottom pie shapes + the edge rectangle created by the imaginary volume of the open casement window opened to the max limit? I am probably overthinking this...

 

[Msradell]

I'm looking at section 1202.5 Natural Ventilation in the IBC - is there any guidance for how to calculate that openable area when looking at vent-type windows...so casements, awnings? The question came up with regard to limit stops on the operable windows and what implication that might have on the natural ventilation requirements. So loosely if you have a 4'x5' window and half of it is an operable casement then regardless of limiters you have 10sf of openable area? Or do you look at the top and bottom pie shapes + the edge rectangle created by the imaginary volume of the open casement window opened to the max limit? I am probably overthinking this...

I've always seen the entire area of the window being used in the natural ventilation calculation without regard to any stops that restrict how far the window can be opened.

 

[findingarch]

Thanks, I appreciate it.

 

[mark handler]

I'm looking at section 1202.5 Natural Ventilation in the IBC - is there any guidance for how to calculate that openable area when looking at vent-type windows...so casements, awnings? The question came up with regard to limit stops on the operable windows and what implication that might have on the natural ventilation requirements. So loosely if you have a 4'x5' window and half of it is an operable casement then regardless of limiters you have 10sf of openable area? Or do you look at the top and bottom pie shapes + the edge rectangle created by the imaginary volume of the open casement window opened to the max limit? I am probably overthinking this...

Most Manufactures will provide that information https://www.jeld-wen.com/en-us/egress-calculator
I do Not count the entire window as venting, because it does not.

 

[findingarch]

Most Manufactures will provide that information https://www.jeld-wen.com/en-us/egress-calculator
I do Not count the entire window as venting, because it does not.
View attachment 7743View attachment 7744

thanks mark, that link is very helpful! it's been my experience with the window manufacturers as well - I recall speaking with them in the past and them doing a calc for me to determine ventilation area. But others involved in the project have said that for the purposes of the code you would just take the openable area minus the frame for a vent-type window. So if you take a sliding window and put an 8" limit stop on it, it very clearly limits the venting area of the window but if you take a casement window and then put an 8" limit stop on it they are saying it doesn't matter.

 

[mark handler]

thanks mark, that link is very helpful! it's been my experience with the window manufacturers as well - I recall speaking with them in the past and them doing a calc for me to determine ventilation area. But others involved in the project have said that for the purposes of the code you would just take the openable area minus the frame for a vent-type window. So if you take a sliding window and put an 8" limit stop on it, it very clearly limits the venting area of the window but if you take a casement window and then put an 8" limit stop on it they are saying it doesn't matter.

If you limit the opening, you limit the ventilation. It's not rocket science.