How to calculate effective operable area for top hung window

January 17, 2014

SSN Energy Model

Mechanical Engineer

LEEDuser Basic Member

5 thumbs up

January 17, 2014

Hi,
We are in the initial design of an office building. The Project team has planned to provide top hung window & the building will have more naturally ventilated spaces.
How to calculate the effective opening area / operable area to check 62.1 compliance & also the opening angle will vary based on its direction.

Is there any procedure or table to calculate the opening area considering the angle.

Also please let me know the same for side hung windows.

Thanks..

Post a reply

Andrew Mitchell, P.E.

Principal
Mitchell Gulledge Engineering, Inc.

LEEDuser Expert

126 thumbs up

January 17, 2014 - 8:09 am

For an awning type window like you describe I have seen projects use 100% of the area that is movable and this was accepted by USGBC. I would not use this as the case if the window does not open at least 45 degrees. If it is less than that then you should do a geometrical representation to show what area you are using. That is how I would approach it.

For side hung (swinging) windows I believe they can open 90 degrees and thus 100% is definitely applicable.

SSN Energy Model

Mechanical Engineer

LEEDuser Basic Member

5 thumbs up

January 18, 2014 - 12:31 am

How to do geometrical representation to show openable/operable area?. Because in our project, the angle is 30 degree. Please help to proceed further?
Is there any standard to follow at this kind of situation?

Andrew Mitchell, P.E.

Principal
Mitchell Gulledge Engineering, Inc.

LEEDuser Expert

126 thumbs up

January 20, 2014 - 9:46 am

I would draw the window open in both plan and elevation view and show the actual area open to the outside. This would be a rectangle for the bottom horizontal plan and a triangle on each side for the vertical plane.

Nadia Ayala

Architect / LEED AP BD+C
KILTIK Consultoría

LEEDuser Basic Member

52 thumbs up

July 22, 2014 - 3:35 pm

Andrew, I may have the same case they posted here, but my opening angles could be even smaller, since its a project of 30 above grade floor levels with operable windows at every level.

I did not fully understand your explanation. Which area is the one I could claim of the awning window as open? How will I calculate the reduced percentage if not? Are you suggesting that we have to measure the area of both "side" triangles formed when opening the window and that would account for the openable area? If not, please clarify. Thank you in advance.