[Bldg-sim] Underfloor air - more questions

Chris Jones cj at cr-jay.ca
Thu Oct 15 16:14:20 PDT 2009

```Check this document:
http://www.bkbiz.net/Website/BMEA/Underfloor%20Air%20Distribution.pdf

>We have this historic building that we are
>renovating and are considering underfloor air
>distribution. The space is a high bay space
>(around 50 feet tall) that will be occupied by
>students with computers. The design currently
>has an access floor 6” above the existing floor.
>We are thinking of raising it a little more and
>running the supply air through underfloor ducts
>(we can’t do a plenum because of the condition of the existing floor).
>
>As far as I can tell the energy benefits of the underfloor air system are:
>
>1.       Higher supply air temperature (68F)
>2.        Lower static pressure
>3.       Stratification (lights, equipment and
>people heat stratifies above the return air grills.
>
>The alternate is a supply duct that throws air
>across the space (60 feet wide)  from a height of 20 feet.
>
>So my questions are:
>
>1.       If the UFAD goes through ducts (as
>opposed to a plenum) is the reduced static
>pressure realistic? How much would you expect to see it reduce by?
>2.       How much stratification can you expect
>here? I assume there is a radiant portion from
>these things in addition to the convective
>portion. Would a 50% reduction in the sensible
>loads be realistic? I know the normal procedure
>would be to assign the rest of the loads to the
>return plenum, but it this case the return will
>be ducted at 8’, while the warm air will be
>allowed to plume up to 50. Does that change  things?
>3.       I assume I should model the upper part
>of the zone as a plenum. In which case – does
>the upper plenum start at 20’  for the alternate
>system (spiral duct at 20’), and at 8’ for the UFAD?
>
>All responses are appreciated
>
>Thanks
>
>Vikram Sami, LEED AP
>Direct Phone 404-253-1466 | Direct Fax 404-253-1366
>LORD, AECK & SARGENT ARCHITECTURE
>1201 Peachtree Street NE, Suite 300, Atlanta, GA 30361
>Responsive Design · Technological Expertise · Exceptional Service
><file:///\\www.lordaecksargent.com\>www.lordaecksargent.com
>P Think GREEN before you print.
>
>
>
>
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Chris Jones
14 Oneida Avenue
Toronto, ON M5J 2E3.
Tel.  416-203-7465
Fax. 416-946-1005

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