[bldg-sim] Green Roofs

Chris Jones cj at cr-jay.ca
Fri Mar 25 07:48:21 PST 2005


I finally got around to reading this interesting paper.  It is too bad that 
someone didn't check the energy simulation results more closely.  In Table 
1, Part 6, the total for the fourth row is incorrect.

I am wondering about the assumed R-30 value for the "green roof" average 
insulation value over the entire year.  If you examine the winter heat flux 
diagrams, there difference in total flux for heating days is quite small 
between the reference and green roofs.  I think that assuming an R-30 
heating insulation value is too optimistic.

In terms of heating, cooling, and heat island effects, and $cost how would 
the green roof compare with an R-30 conventional roof with a low-emissivity 
finish?


At 11:53 28/02/2005, Ferguson, Alex wrote:
>The Institute of Research and Construction (IRC, part of the National
>Research Council of Canada) has conducted a fair amount of research in this
>area. Much of this work, including hydrology modelling, experimental
>investigations and Visual DOE simulations, is summarized in the following
>report:
>
>http://irc.nrc-cnrc.gc.ca/fulltext/nrcc46737/
>
>...
>Alex Ferguson
>CANMET Energy Technology Centre
>Natural Resources Canada
>P:+1 613 995 3294
>F:+1 613 996 9909
>Alex.Ferguson at nrcan.gc.ca
>
>
>
>
>-----Original Message-----
>From: postman at gard.com [mailto:postman at gard.com]On Behalf Of Brian Thornton
>Sent: Monday, February 28, 2005 11:40
>To: BLDG-SIM at GARD.COM
>Subject: [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 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
>To: BLDG-SIM at GARD.COM
>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 at econergy.net> wrote:
>Hi,
>
>I am looking for some advice on modeling a green roofin Equest.
>Specifically, what should I set Surface Roughnessand 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
>
>
>
>Do you Yahoo!?
>Yahoo! Search presents - Jib Jab's 'Second Term'
>
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Chris Jones, P.Eng.
14 Oneida Avenue
Toronto, ON M5J2E3
Tel. 416 203-7465
Fax. 416 946-1005 



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