[BLDG-SIM] Green Roofs

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@xxxxxxxxxxx

From: postman@xxxxxxxx [mailto:postman@xxxxxxxx] On Behalf Of Nikhil Kapur
Sent: Tuesday, February 22, 2005 2:40 PM
To: BLDG-SIM@xxxxxxxx
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.

Regards,

Nikhil

Dan Sobrinski <sobrinski@xxxxxxxxxxxx> wrote:

Hi,

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@xxxxxxxxxxxx

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