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Cool-Roof Coatings Generate Some Heat for Florida Utility Co.

Monday, January 3, 2011

More items for Building Envelope; Good Technical Practice

The use of white, solar-reflective coatings often proves beneficial in reducing roof temperatures and contributing to lower cooling-energy demand.

But the application of such coatings has allegedly caused some very non-beneficial—and unwanted—effects when applied to a number of asphalt-shingle roofs in Florida, based on a news report on complaints lodged with the utility company Florida Power & Light. The coatings are being blamed for leaking and deteriorating roofs.

The South Florida Sun Sentinel reports that Florida Power & Light (FPL) reimbursed contractors to paint asphalt-shingle roofs white to reflect sunlight—“against the advice of the federal government and major roofing manufacturers.” FPL has provided rebates as part of a program to encourage customer actions to reduce electricity use and costs.

The Sun Sentinel story can be read at FPL sued over program aimed at saving energy.

“About a dozen FPL customers have complained to state regulators that their roofs started to deteriorate or leak after they were coated,” the newspaper reported. “And five others in South Florida filed a lawsuit against FPL and the contractor who did the work. Others have complained directly to the utility or contractor, according to court records.”

The report said FPL has provided rebates for application of white coatings to some 4,700 asphalt roofs. The funds are generated by conservation charges on electricity bills.

Complaints included reports of leaking roofs, with one homeowner saying paint trapped water in the shingles, causing the nails to rust and water to seep in.

Jackie Anderson, an FPL spokeswoman, told Durabilty + Design that complaints have come from only a “handful” of customers. She said customers make arrangements with independent contractors, who are responsible for the work and for complying with building codes. “We provide incentives to help with the cost,” she said.

“We’re conducting a thorough investigation of the claims, but the matter is in litigation, so we really cannot comment further,” Anderson said.

The newspaper report says painting shingle roofs “has never been recommended or approved by the federal Department of Energy, which also promotes energy conservation,” and adds that the Asphalt Roofing Manufacturers Association (ARMA) warns against applying elastomeric roof coatings to asphalt shingles.

“Problems reported after asphalt shingle roofs have been field coated include unsightly curling and/or cupping of the shingles, which may lead to premature failure and leaks,” the newspaper said, quoting an ARMA technical bulletin. “The paint can trap moisture and make the shingles rot.”

But opinions on the issue are apparently not universally agreed upon. The Solar Reflective Coatings Council, part of the Roof Coatings Manufacturers Association (RCMA), says in a “Frequently Asked Questions” discussion of solar-reflective roofs that white, reflective coatings can be applied a wide range of roofing surfaces, including “certain kinds of asphalt roofs.”

“White coatings can be applied to practically any roofing surfaces, membranes, or substrates,” the FAQ section of the Solar Reflective Coatings Council’s website states. “They are commonly applied to sprayed polyurethane roofs to provide waterproofing. They can also be applied to metal roofs, single-ply rubber roofs and modified-bitumen roofs. They can even be applied to certain kinds of asphalt roofs.”

The document adds, however, that “It is important to establish compatibility between the white coating and the underlying roof membrane.” See FAQs on white roof coatings.

The Sun Sentinel report said coatings were applied to 4,711 asphalt shingle roofs, including 1,004 in Broward County and 1,948 in Miami-Dade County, from 2007 to 2009, according to court documents.

Comment from Louis Hickman, (1/4/2011, 10:59 AM)

I am curious to know if the problem roofing received elastomeric coating or conventional exterior acrylic. I beleive either would be fine over good shingles if applied properly. I have had success painting asphalt shingles for many years. Light colors will save energy and the coating will prolong the life of the shingle. I oversee painting of a large school system that has utilized fluropolymer as well as straight up light colored exterior SG acrylic. I applaud FPL.

Comment from Karl Kardel, (1/4/2011, 12:11 PM)

I have been coating asphalt shingle roofs, and low slope roofs since the mid 1960's after finding the white roofs age well due to lessened heat loads and thermal swings in dimensions. A major bay area roofer labelled me 'a commie' because I noted our customers could get an extended life of their roofs. The coatings neither water proof the roof or rehab a deteriorated roof. The devil in everything is in the details. If a roof is not 'tuned up' first or the fabric is too tired or the asphalts have migrated, they are not a candidate for coating. Air conditioning loads have been decreased substantially and well documented. I do not recommend coating in cold climates in old buildings that have air leaks or thermal bridging. White roofs will cause new problems. But if the Florida roofs are curling or failing it is because they were worn out in the first place. A heavy coating will have a surface tension that can pull up tired shingles, particularly with a heavy elastomeric. With comp roofs we advise 2 coats of watered down acrylic applied just enough to flood in between the grannules in the first coat, and then a second thin coat for color. Roofs done in this manner survived over 30 years here, and were free of the violent temperature changes found her(40 at night, 160 surface temps mid day]. White roofs are wonderfully effective, but like everything else you need to know the details. Everything good can be used like snake oil. I hope this does not slow down the program. Karl Kardel Consultancy Problem Buildings Solutions Since 1959

Comment from Louis Hickman, (1/4/2011, 12:34 PM)

Great comment Karl. I thought I would mention the fact that there now exists single component water based kynars. Their properties are a consideration as well as their price.Not sure what they will say on paper about using them on asphalt but I have great confidence in them. Happy painting.

Comment from wayne vutech, (1/5/2011, 11:36 AM)

I was looking into doing some of the shingle applications and ran across a product called nansolate. It is clear and they recommend three thin coats onto the roof. However they want you to form a seal which is difficult to do as this product is clear. Have any one used this product and was FPL problems all with elastomerics?

Comment from Steve McGuinness, (1/6/2011, 5:55 PM)

The real problem might be that the elastomeric coating to too efficient. It works too well at cooling the roof surface. Something to consider, an elastomeric roof coating is extremely efficient at reflecting heat energy from the sun. When applied to a residential shingle roof, it will make the roof deck cool, both the roof surface and the deck inside the attic. A typical residential roof has vents along the eves and the ridgeline. These vents encourage air convection through the attic; the roof gets hot, heats up the attic and convection occurs. After an elastomeric coating is applied to the roof shingles, the roof does not get hot… Convection does not occur. Now you have a situation where warm moist air is entering the attic through the eve vents but there is not convection. This warm moist air condenses on the underside of the roof deck, because the roof deck is so much cooler than the air. This condensation will saturate the roof deck and cause mold, mildew, and rot. Possible solutions would be to put power vent fans on the roof or gables to move to encourage air movement. If the air circulates through the attic, it will not have a chance to condense on the roof deck.

Comment from Don Freitag, (1/10/2011, 9:16 AM)

First and Foremost, why was the coating applied to what I am assuming is a residential shingle ? The coating is being blamed for leaking & deteriorating roofs ? Come on--really ? If applied correctly and it is the proper application the White Elastomeric coatings can extend the life of your roof. Secondly, most roof coatings have a low permeability to them which in some cases have the ability to allow one-way migration assuming there is vapor present and not trapped moisture. If there is trapped moisture then I would say this application was not appropriate for a coating. The Roof Coatings our there are NOT miracles in a bucket however, if they are used & applied to their abilities can do wonders and solve many problems which ultimately creat sustainable solutions which equates to SAVINGS. So, if I may just suggest or educate there are basically coatings and fluid-applied systems. Roof coatings merely do three things (reflectivity, enhance fire rating (flame-spread) & change the aestetics) but, does not include waterproofing however, fluid-applied systems generally include the reflectivity, enhances the fire rating (flame-spread) and enhances the aestetic value and get this---it can waterproof !!

Comment from Tom Schwerdt, (1/11/2011, 8:46 AM)

Steve, are you really proposing that a white roof in the sun will be cooler than the surrounding air?

Comment from Don Freitag, (1/11/2011, 10:26 AM)

Most quality cool (white) roofs should stay within 7-10 degress around ambient temperatures

Comment from Jerry Rockwell, (1/12/2011, 1:52 PM)

Thank you Karl, you are absolutely correct. The application of a white elastomeric roof coating can reduce your air conditioners load, and save you money. But the high tensile strength of a good elastomeric will pull up old shingles. The key is to do your homework. Find out as much information as you can before deciding to coat any substrate. There are always potential situations on your roof which may be caused by the permeability of the coating, (or water vapor transmission), inadequate ventilation, or improper ventilation, and/or incorrect installation of a roofing membrane. I have applied elastomeric coatings to new shingle roofs in actual applications and simulated applications but never aged shingles. Extra precautions should always be taken when applying coating to any aged roofing substrate.