[Bldg-sim] Underfloor air - more questions

[Steve Mignogna]

Vikram,

Also, do not forget that since you are now able to supply the air at a
higher temperature you can set your outside economizer at a higher
temperature as well. Alot of the savings from displacement type air
distribution systems come from the increased outside air economizer use.
Good luck.

-- 
Steve Mignogna
Atelier Ten

On Thu, Oct 15, 2009 at 7:14 PM, Chris Jones <cj at cr-jay.ca> wrote:

>  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
> Please visit our new website | www.lordaecksargent.com
> P Think GREEN before you print.
>
>
>
>
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> Chris Jones
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