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IGA/EGA Ratio Calculations

Annie Leung
September 26, 2018

On page 30 of the BOMA (“Mixed-Use Properties: Standard Methods of Measurement” ANSI/BOMA Z65.6-2012), how are the IGA/EGA Ratios in column “F” computed?

For room # 01-08, 01-34, 01-36 and 01-37, all are MUCA spaces on the first floor with a boundary at the perimeter but 01-37 ratio is computed at 100.00%.

Thank you.

David Fingret
Extreme Measures Inc.
September 27, 2018

Hi Annie,

The IGA/EGA Ratio is calculated by dividing the Office IGA (Office Interior Gross Area) by the Office EGA (Office Exterior Gross Area). The ratio is calculated in order to account for the difference in the perimeter measure line between the office standard (Office IGA) and the Gross Area Standard (Office EGA). This ratio is applied to the MUCA (Mixed-Use Common Areas) rooms that are to be allocated to the Office Use Component.

You'll notice that there is a footnote next to each of the MUCA Room #'s you mentioned denoting that they are along the building perimeter. This is why the ratio for those areas (expressed as a percentage) are lower than 100%. The calculation shows how much of that particular room is going to be proportionately allocated to the Office Use Component.

As you noticed, the room "01-37 Loading Dock" has an IGA/EGA Ratio of 100%, even though it is also along the building perimeter. You will find this room illustrated on page 15. In this scenario, I believe that the IGA boundary condition known as "Unprotected Exterior Opening" in the BOMA Office 2010 Standard is being applied, which measures to the outermost horizontal line of the building. This would result in the same measure line as the Office EGA, producing an IGA/EGA ratio of 100%.

I hope this helps.


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