[BLDG-SIM] "Cool Roofing"

Mark E. Case mcase at etcgrp.com
Mon Oct 7 15:07:19 PDT 2002

I know a researcher at LBNL that has done a significant amount of work on
cool roofs. I have taken the liberty to forward the previous emails to him
to see if he can provide any enlightenment. There are numerous papers in the
peer reviewed literature that you may want to look at.
  -----Original Message-----
  From: postman at gard.com [mailto:postman at gard.com]On Behalf Of Tom Anderson
  Sent: Monday, October 07, 2002 2:32 PM
  Subject: [BLDG-SIM] "Cool Roofing"

  Oh Contrair.
   I ran load calcs for a 100,000 square foot single story big box store in
the Burlington, VT area last year to determine what if any benefits would
result from changing the flat membrane roof color from dark to light.
Occupancy was typical urban sprawl well-known national retailers.

  Peak air conditioning roof  heat gain was reduced by 50%.

  Roof was insulated to about R-22, plenum return, packaged DX rooftops.
Ran the numbers using Carrier HAP.  Annual AC energy savings came in at
about 3%.  Software did show a *slight* heating season penalty, but that was
because the software did not account for the usual snow cover on a Vermont
roof in winter. There was a worthwhile installed tonnage reduction also.

    Thomas E. Anderson
    Cx Associates, Ltd.
    Building Commissioning Specialists
    933 Road 101
    Jeffersonville, Vermont 05464 USA
    hvac at cx-assoc.com
    Tel: 802-644-5616 Fax: 802-644-6797
  Marcus Sheffer wrote:
     Whenever we have modeled this in the Northeast we also have seen
negligible savings using PowerDOE and others.
    We have come to the conclusion that the savings depend upon the amount
of roof insulation and type of building.  If we enter minimal insulation the
effect of a white roof is larger especially in a cooling dominated building,
high internal loads, etc.

    If you are installing even moderate amounts of insulation (R15 or more)
then the effect of a white roof in the Northeast is virtually nil for most
any building type.

    Now when it comes to the urban heat island effect it can have a
tremendously positive impact . . . but that is another issue.

    At 01:55 PM 10/07/2002 -0400, you wrote:

      Has anyone had any success modeling cool roofing options (i.e.
reflective or light colored surfaces) in PowerDOE?  So far, I have seen
negligible results from the adjustment of roof construction absorptance
values (emissivity is also known to play a role, but there is no input for
this in PowerDOE).  I have seen data showing cooling energy savings from
0.06 to 0.54 kWh/sqft/yr, depending on building type.  I am getting only a
very small fraction of this.  Data collected in the study was from
facilities in the southern and western US, and I work primarily on buildings
in the Northeast.
      My questions:
      How well can I expect PowerDOE to simulate this?  Is there a better
way to simulate cool roofing?  Is the sun simply too low in the sky in New
England to yield substantial savings?

      Your thoughts are appreciated.

      Wade McLaughlin

    Marcus B. Sheffer                          energy & environmental
    Energy Opportunities                     717-292-2636
    1200 E Camping Area Road            Fax: 717-292-0585
    Wellsville, PA USA 17365-9783        sheffer at sevengroup.com
    a Seven Group member company   www.sevengroup.com

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