MCH-03 Ventilation on alteration

Home Support Forum Nonresidential Code Questions MCH-03 Ventilation on alteration

This topic contains 2 replies, has 1 voice, and was last updated by  EproUser1500 1 year, 8 months ago.

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  • #5481


    I am currently working on a project in which a 2-story building is having the first floor remodeled The first floor is changing occupancy and layout. They want to keep the existing VAV system as it serves both floors. The design intent is to remove the existing VAV boxes and install new VAV boxes to serve the new first floor layout. We don’t have much information about the existing system, so I think the best option is to follow prescriptive compliance. I think all that is needed is the MCH-03 form.

    The MCH-03 form has a column for Required ventilation airflow (cfm). Since we are only replacing the VAV boxes, we don’t have any info about the existing outside air for the system.

    How should we go about verifying that we are providing adequate ventilation to the spaces where VAV boxes are being replaced?

    Are we going to have to try and track down a set of existing plans to figure out outside air intake and all diffuser CFMs? If that is not possible, what is the best approach?

    • This topic was modified 1 year, 8 months ago by  Patti.
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  • #5486


    Thanks for your reply. I also found these examples from page 4-127 of the 2016 Nonresidential compliance manual and this seems to relate to my question. This was in the section regarding space-conditioning system alterations.

    It seems that you are correct and that it isn’t as simple as installing new VAV boxes, we must also check the existing VAV system and make adjustments to ventilation as needed.

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    In a nutshell, with the new VAV boxes, the AHU will be subject to ventilation testing and confirmation by the ATT, so you will have to show compliance and they will have to calibrate the OA on the unit to comply.

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