The LEED-NC 2009 EQc7.1 credit template asks us to document the Project Space Design Air Speed at 3 ft above the floor. According to ASHRAE 55, this should be a maximum of 40 FPM. However, most air terminal/diffuser manufacturers only publish data for throws down to 50 FPM. How are project teams expected to document a design air speed at the occupant that is lower than shown the available mfr data without doing a CFD model?

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Cam Fitzgerald

Energy Engineer

7group

LEEDuser Basic Member

18 thumbs up

Wed, 10/24/2012 - 15:27

A CFD model is not required. If the manufacturer cannot provide the throw for less than 50 fpm, the additional throw required to further reduce the velocity to 40 fpm could be extrapolated from the available data. Another approach would be to use the methodology described in Section 5.2.4.2 to demonstrate that the local turbulence intensity is low enough that the occupants will not experience discomfort due to drafts. Another route could be to work backwards with the temperature differentials noted in Section 5.2.3 for using elevated air speed to provide comfort at increased space temperatures.

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