[BLDG-SIM] Cool Roof simulation

[Graham & Megan]

We have looked into low absorptance, high emissivity roof coatings on
several occassions.  Your results aren't too far off those we have come up
with using EQuest and Apache.

Judging by the mesaured data available from SkyCool, it seems there is a
property / physical mechanism that is not represented by conventional
absoprtance and emissivity.  There is speculation that the coatings have an
extended surface area from which they emit.  This extended area could be a
result of surface roughness or the material emitting from multiple layers
within the coating ... If this is in fact what is happening, the sums will
show a greater benefit though no program to my knowledge would allow you to
account for this.  In simple terms it would be represented as an emissivity
of greater than 1 across the projectd area of the roof ...

Anyone else getting similar advice from other coating suppliers?

Regards,
Graham

----- Original Message ----- 
From: "Aulbach, John" <jaulbach at nexant.com>
To: <BLDG-SIM at GARD.COM>
Sent: Tuesday, October 17, 2006 6:24 AM
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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