[BLDG-SIM] Green Roofs

Brian Thornton thorntonenergy at comcast.net
Mon Feb 28 08:40:26 PST 2005


One issue with Green Roofs that has come up, is analyzing potential energy
savings benefits from evaporation, and plant evapo-transpiration.  There is
at least one program out there that apparently addresses this.  


1)       Are there opinions on whether these effects generate credible
supportable energy savings from typical green roof installations?


2)       Does anyone know of a standard methodology that could be
incorporated in a broad energy simulation such as eQuest?


3)       Has anyone received approval from USGBC or a utility incentive
program to claim energy savings from these effects, and if so what kind of
documentation was used? 


Thanks-Brian Thornton


Thornton Energy Consulting

p. 503-231-6600 f. 503-231-3555

thorntonenergy at comcast.net



From: postman at gard.com [mailto:postman at gard.com] On Behalf Of Nikhil Kapur
Sent: Tuesday, February 22, 2005 2:40 PM
Subject: [BLDG-SIM] Green Roofs


Hi  Dan,


You can use a reflectance of 0.70 or greater i.e. absorptance of 0.3 or less
for the roof. Also the effect of the U-value of the roof construction will
change so you will have to set a multiplier for the u-vlaue of the roof.
This can be referenced in the ASHRAE 90.1 - 1999 Users manual in the
Building Envelope section - page 5-20 table 5-E which gives the Roof
U-factor multipliers for the various climate zones.





Dan Sobrinski <sobrinski at econergy.net> wrote:



I am looking for some advice on modeling a green roof in Equest.
Specifically, what should I set Surface Roughness and Ext. Color
(absort) too?  Are there any other parameters that need to be modified to
simulate a vegetated roofing system?


Thanks in advance 


Dan Sobrinski, CEM, LEED AP 

Associate Engineer

Econergy International Corporation

3825 Iris Avenue, Suite 350

Boulder, CO  80301

303-473-9007  voice

303-473-9060  fax

sobrinski at econergy.net


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