We have a Commercial Interior Project with underfloor air distribution (UFAD) system designed to include adjustable supply air diffusers in the floor, which can be used to adjust the amount of supply air being supplied to the occupied space served by the diffuser.
We just received the preliminary design review. The reviewer noted that a reduction in supply air flow would be expected to result in a reduction of ventilation air flow to the space served by the adjusted diffuser.
The reviewer also appointed that it is not clear how the ventilation rate procedure calculations have accounted for potential reductions in supply air flow rates due to occupant adjustments of the floor air supply diffusers serving meeting rooms.
The reviewer is asking to describe how the ventilation rate procedure calculations have been adjusted to account for potential reductions in supply air flows due to occupant adjustments. Our HVAC designer thinks this is a subjective issue since he can not estimate or predict how the occupant will adjust each diffuser for personal comfort.
Any recommendation on how to approach this technical advice is more than welcome.
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Roger Chang
Principal, Energy and Engineering LeaderDLR Group | Westlake Reed Leskosky
LEEDuser Expert
398 thumbs up
January 5, 2016 - 12:39 pm
I believe the reviewer is looking for clarification on whether a zone distribution effectiveness adjustment was included (Ez) per Chapter 6 of ASHRAE 62.1. This correction factor accounts for the location of both supply and return in heating and cooling modes. A true displacement ventilation system allows an Ez value of 1.2 to be utilized, which allows an effective decrease in ventilation air delivered to the breathing zone while achieving an equivalent ventilation effect.