Letters

In his article "Roofing's dirty secret," April issue, page 26, Tom Hutchinson, principal of Hutchinson Design Group Ltd., Barrington, Ill., points out some issues regarding reflective roofs that are important for contractors. We at SPRI believe it is important to provide additional insight and information concerning these issues.

Just as cars and trucks get dirty, contractors also should expect roofs exposed to the same environment will get dirty, too. Car washes became popular years ago when some entrepreneurs learned people valued clean cars for maintenance and technical reasons, such as eliminating corrosive salt. Will the aesthetic and technical value of a clean roof result in a new industry? That question will remain unanswered until the total value equation is developed, understood and implemented.

SPRI takes exception to Hutchinson's claim that "dirty roofs" have been ignored by the industry. Quite the opposite, the soiling of roofs has not been ignored by manufacturers, ENERGY STAR® or the Cool Roof Rating Council (CRRC). In fact, SPRI members began a study of the soiling of roofs in 1998 and published two papers about the subject.

ENERGY STAR allows cleaning of roofs before their three-year aged solar reflectance value is measured based on a belief that rain just before sampling might clean a roof, as well. CRRC decided cleaning a roof after three years of aging should not be done because doing so may inappropriately affect the measured solar reflectance. However, this concept has not been presented aggressively enough to roofing contractors. Manufacturers aim to more proactively help contractors understand the facts.

Many SPRI members have produced and distributed literature about cleaning roofs. They have suggested how to properly use materials and equipment required for the cleaning process, such as pressure washers. Hutchinson points out one should not begin cleaning a roof without going through a checklist of what should be done in the process; SPRI, too, believes this is important.

Some SPRI members have developed white and other light-colored roof membranes intended to provide extended membrane life by keeping a roof cool. SPRI members maintain the resulting energy savings have become a much appreciated secondary benefit of their efforts. SPRI members expect longer lives from light-colored membranes whether a roof is cleaned or left to soil naturally. Additional reflective and other products have been developed in the roofing industry as a response to the demand for cool roofs. Of note, a recent study by Oak Ridge National Laboratory revealed soiling did not change the underlying solar reflectance.

The value of higher solar reflectance was discovered by scientists looking for ways to reduce peak energy costs. Because peak energy demand usually occurs on hot days with the sun shining, reducing rooftop temperature with a reflective roof is a logical solution that has value, particularly in warm climates. Interestingly, research shows the energy savings value of higher reflectance is significantly greater when there is little insulation, as is typical in southern climates. Therefore, installing a reflective roof reduces peak energy cost for a building. Of course, adding insulation can have a similar result and always should be considered.

SPRI supports CRRC's approach in the development of aged testing protocol without cleaning to avoid leaving questionable promises unchallenged. It is important for contractors and all involved in the roofing industry to recognize dirty roofs have not been ignored by SPRI or CRRC. Likewise, there is no reason for manufacturers to keep the assessment, maintenance and care of reflective and dirty roofs a secret.

David L. Roodvoets
SPRI
Waltham, Mass.

Following is Hutchinson's response to the letter:

I appreciate Roodvoets taking the time to read the article and provide some additional information with regard to the issues of cleaning roofs. In response to some of the additional information and insight provided, I offer my thoughts.

Although contractors may expect roofs to get dirty, owners who have been sold on the idea of "white" and or "cool roofing" do not. I suggest the roofing contractor community have the knowledge to clean roofs before installing a coating. The real issue appears to be owners are unwilling to pay for cleaning, and when they do, the costs are extreme. For example, the cleaning of the Tacoma Stadium Dome reportedly cost in the range of $80,000.

My definition of the "roofing industry" is different than Roodvoets' definition in that I certainly do not consider ENERGY STAR and CRRC to be part of the industry. A great concern of mine is that these government programs, especially ENERGY STAR, have worked to affect code change and influence the marketplace without the input or involvement of contractors; designers; and associations such as SPRI, Roof Consultants Institute and NRCA, whose knowledge would have been enlightening. It appears to me contractors and roof system designers have been ignored completely and not presented aggressively enough.

In preparation for the article, I interviewed 10 manufacturers at a fairly large trade show. Not one was able to produce company information about cleaning. Some indicated they thought information was available but they would have to get back to me. None did so. Many offered cleaning recommendations that certainly would create an environmental concern should the liquid wash into the drains and retention ponds. What certainly have not been addressed are the effects of repeated cleaning on a roof membrane. If SPRI members have this information, perhaps they should share it with their sales and technical staffs so it can be imparted to contractors and designers.

Roodvoets mentions cool roofing was developed to reduce peak energy costs, but others would suggest it was developed to reduce urban heat islands. The concern here is a lack of a clear definition of the purpose of cool roofing. In either case, if reflectivity were part of the design solution, owners must be informed of the need for cleaning, costs, and potential and currently unknown possibility of roof membrane service life reduction caused by repeated cleaning.

I have great concern with Roodvoets' statement about research showing energy savings can be significant in southern climates when little insulation and a white membrane are used. This type of comment has far-reaching consequences because some will take it as gospel.

First, he indicates this information is based on research, not empirical, real-world experience; second, the information ignores the effects of soiling (the effects of roof surface biomass growth were not addressed by SPRI); and third, it does not take into account future increases in energy costs, cleaning costs and potential for reduced service life. The long-term benefit of adequate thermal insulation cannot be underestimated.

As readers can see, the issue of cool roofing is a complex and often confusing topic. The topic recently was discussed at the Cool Roofing Symposium sponsored by the Roof Consultants Institute Foundation. The proceedings would be a fine addition to the library of anyone interested in cool roofing.