[BLDG-SIM] Cool Roof simulation

Eben Twombly, PE twombly at kw-engineering.com
Mon Oct 16 14:14:17 PDT 2006


John - That savings may not be so far out of line. Check the outside air and
insulation assumptions. You could possibly be exhausting a lot of that load
(plenum heat gain) if you are running with a high OA percentage. Also, I
don't know where your building is, but based on the data provided your HVAC
EUI is 78 kWh/SqFt-Yr, a very high value. The savings are around 0.35
kWh/SqFt-Yr, not totally unreasonable depending on your chiller plant
efficiency. Our experience with cool roofs has been limited to buildings
where the roof is directly coupled to the conditioned space.

Eben Twombly, P.E.
kW Engineering, Inc.
287 17th Street, Suite 300
Oakland, CA 94612

Ph. (510) 834-6420 / FAX (510) 834-6421

http://www.kw-engineering.com

-----Original Message-----
From: Aulbach, John [mailto:jaulbach at nexant.com] 
Sent: Monday, October 16, 2006 1:24 PM
To: BLDG-SIM at GARD.COM
Subject: [BLDG-SIM] Cool Roof simulation

 
Hello All:

I am looking for a fairly straight forward to model a "Cool Roof" in
eQuest.

My general understanding would be to do a Parametric Run, changing the
outside emissivity from, say 0.75 to 0.3. But I am getting VERY little
energy benefit.

My building is a 140,000 sf office, 2-story (70,000 sf roof). It has a
CW VAV system with HW reheat, and return air is through ceiling plenums.

I am only seeing about a 50,000 kWh saving out of 11,000,000 kWh HVAC
usage.

Any experience, suggestions?

John R. Aulbach, PE, CEM
Project Manager
Nexant, Inc.
100 North Barranca, Suite 820
West Covina, CA 91791 USA
Phone: 626-430-9054
Fax: 626-430-9060
email: jaulbach at nexant.com
 

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