09/27/2013

Reflections on Roof Performance

How to avoid excessive heat load

By Richard L. Fricklas

 
  • /Portals/1/images/OnlineImages/2013/1013/rr/sunglare.jpg

    This London skyscraper reflected so much heat that it melted the mirror, panels, and hood ornament of a nearby Jaguar.

  • /Portals/1/images/OnlineImages/2013/1013/rr/sunglareclipping.jpg

    London building officials are now searching for a solution to the dangerous heat problem.

A recent Associated Press caption reported: “Tower’s sun glare burns Jaguar, spurs hunt for solution.”

There have been many reports of glare on newly constructed roofs that have required remediation, but in this case the heat source was from reflective window glass, not just from white or aluminum roof coatings on a roof surface.

What makes this incident special is the magnitude of the heat load. The article went on to state that a Jaguar parked in London in the path of the reflected heat “for a couple of hours” had melted the Jaguar’s mirror, panels, and hood ornament and burned a hole in the welcome mat of a barbershop across the street.

That excessive heat load is an entirely new issue – not just for luxury cars parked near highly reflective facades, but for roofs too, as too much heat causes premature aging.

What the Standards Say 


Richard (Dick) L. Fricklas

Richard (Dick) L. Fricklas was technical director emeritus of the Roofing Industry Educational Institute prior to his retirement. He is co-author of The Manual of Low Slope Roofing Systems, and continues to participate in seminars for the University of Wisconsin and RCI Inc., the Institute of Roofing, Waterproofing, and Building Envelope Professionals. His honors include the Outstanding Educator Award from RCI, William C. Cullen Award and Walter C. Voss Award from ASTM, the J. A. Piper Award from NRCA, and the James Q. McCawley Award from the MRCA. Dick holds honorary memberships in both ASTM and RCI Inc.


ASTM Specification for Poly (Vinyl Chloride) Sheet Roofing (D4434) requires heat aging at 176 degrees F. for 56 days. This roughly relates to chemical kinetics that states once material has reached its energy of activation, the rate of acceleration doubles for every rise of 10 degrees C. Standard D6754 for Ketone Ethylene Ester (KEE) also uses 176 degrees F. for 56 days.

Heat aging for Thermoplastic Polyolefin Based Sheet Roofing (TPO) D6678 is somewhat more severe – 240 degrees F. for 224 days, perhaps recognizing the demand for more efficient roofing systems and as a result of far more thermal insulation directly under the roof membrane.

All of the above polymers are designated as “thermoplastic,” and their seams can be heat welded using a hot-air welding gun. The heat exposure is very brief whether hand-welded or machine-welded. Many of these materials can now be seamed using pressure-sensitive cold adhesives. However, we lack accurate data on reflected heat. If the London building (which will not be completed until 2014) is any indication, we need to use materials that can accommodate these new magnitudes of heat load.


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Visit our website today to learn about the design flexibility of a Morton building and the endless possibilities of partnering with our designBUILD team.


Wood construction is both cost and energy efficient. Check out Morton Buildings and our designBUILD team online today to discover all the benefits of post-frame construction.


When choosing a metal-clad building for your next construction project, consider Morton Buildings, Inc., and their designBUILD team, we’ll make your dream a reality.

We Can Help You Reduce Energy by 30%

Our mission is to help our customers manage their buildings' energy costs, improve reliability, and enhance performance while having a positive impact on the environment.
CLICK HERE to find out how.

Add highly responsive multi-zone comfort to any building project, in any climate. Our CITY MULTI H2i R2- and Y-Series VRF systems give you flexibility to fit the needs of any building. Enjoy 100% heating capacity at 0°F outdoor ambient, and 85% heating capacity at -13°F outdoor ambient.  For more information, log on to www.mitsubishipro.com


Tennant Company is a recognized leader in designing, manufacturing and marketing solutions that help create a cleaner, safer, healthier world. With thousands of satisfied customers already using award winning ec-H2O technology, why not see what you're missing? Test ec-H2O on your soils in your facility. Get a free demo.


Tennant Company is a recognized leader in designing, manufacturing and marketing solutions that help create a cleaner, safer, healthier world. With thousands of satisfied customers already using award winning ec-H2O technology, why not see what you're missing? Test ec-H2O on your soils in your facility. Get a free demo.

 

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