[BLDG-SIM] "Cool Roofing"

[habaza11 at cs.com]

Hi;
If you consider both heat and moisture flux (absorption), roof surface properties will have even more impact on load. I applied this to bridge decks to reduce surface freezing and had significant results.
H. Abaza
Tom Anderson <hvac at cx-assoc.com> wrote:

>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
>     President
>     Cx Associates, Ltd.
>     Building Commissioning Specialists
>     http://www.cx-assoc.com
>     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
>>> DMI
>>
>> Marcus B. Sheffer                          energy & environmental
>> consulting
>> 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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"Guedi Capeluto" <arrguedi at techunix.technion.ac.il> wrote:

>Hello,
> 
>Some years ago we published a work that presented a sensitivity analysis
>of building's energy performance in a hot-humid climate (Tel Aviv)
>to the values assigned to various design parameters among them Roof
>color. It was done for a standard heavily constructed apartment building
>block, using the simulation model ENERGY developed by Shaviv and Shaviv.
>The results show that the influence is dependent on the roof insulation
>and can be positive or negative during different seasons.
> 
>For more details check:
> 
>
> Shaviv E. and I. G. Capeluto, 1992. "The Relative Importance of Various
>Geometrical Design  Parameters in Hot-Humid Climate", "ASHRAE Trans.",
>Vol.98, AN-92-1-1, Baltimore. (pp. 589-605) 
>
> 
>
>Best,
>
> 
>
>Guedi Capeluto
>
> 
>
>---
>
>Arch. Guedi Capeluto, D.Sc.
>Faculty of Architecture and Town Planning
>Technion - Israel Institute of Technology
>Technion City, Haifa 32000. Israel.
>Tel: +972.4.8294013    Fax: +972.4.8294617
>email: arrguedi at tx.technion.ac.il
>
>
>
> 
>
> 
>
>
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