Why “Cool” Roofs Grow Mold

The best way to control mold is to control moisture, according to the EPA (Environmental Protection Agency). A study – published in May 2008 – demonstrates how white roofs have moisture issues in areas with very cold ambient temperatures – like Chicago, IL. White roofs accumulate moisture in colder regions, due to the reduced surface temperatures during the day. Furthermore, the long-wave radiation can lead to overcooling of the surface below ambient temperature. Such low temperatures during the night can cause the temperature to drop beneath the dew-point, followed by condensation of moisture below the membrane.

The U.S. Department of Energy precautions: Although cool roofs have been used successfully for many years, their use is growing and cool roofs are now being installed in a wider range of climates. There are some important questions about the durability of cool roof systems in certain applications. Cool roofs maintain lower temperatures than dark roofs, and so they may provide less heat to dry out moisture. Potentially, this could make a cool roof more susceptible to moisture accumulation when used in colder climates.

Long Life Of An EPDM Roof

“The first field studies of EPDM were done in the late 1980s, and we are finding a pattern,” says Thomas W. Hutchinson AIA, FRCI, RRC and Principal, Hutchinson Design Group, Ltd., Barrington, Ill. “The pattern is that these roofs can really last a long time. By using today’s advanced design techniques and proper roof maintenance, it is reasonable to expect that an EPDM roof will approach or exceed 40 years of service.”

Roofing Life-Cycle Costs

According to a 2005 Roofing Industry Alliance for Progress survey of building owners, the three most important considerations for selecting a new roof are, in order of priority: 1) installed cost, 2) the quality of installation, and 3) life-cycle costs (LCCs). Of those three, the only surprise is the high ranking of LCCs, which is a relatively new concept. One reason for the emergence of LCC roofing analysis is the growing sustainable building movement, which endorses energy-efficient and long-lasting roofs. Both of these characteristics can contribute to lower roofing life-cycle costs.

Unlike installation costs, which have the precision and immediacy of a payable invoice, LCC estimates include future considerations like longevity, maintenance and repair, and potential savings from energy efficiency. LCC estimates are inherently less precise, but they are a useful guide to value over time.… –  Drew Ballensky

Roofing LCC Checklist
At a minimum, building owners requesting a life-cycle cost estimate should expect it to include:

  • The cost of the roofing system.
  • The cost of installation (labor + overhead).
  • Tear-off/disposal costs (not necessary for all roofing systems).
  • Estimated maintenance costs.
  • Estimated repairs (based on experience and type of roof).
  • Potential energy savings.


With the EPDM technology we utilize today, we can make a roof perform.

Studies show 50-75 years !!

Some of the earlier failures of EPDM were due to seam failure. The difficulty was in creating long-term seams. The National Roofing Contractors Association’s Project Pinpoint showed seam failures to be the No. 1 complaint with EPDM. After many steps in evolution – including an in

famous experiment with non-penetrating fasteners – butyl based tapes have become the industry standard since their introduction in the 1990s.

Tom Hutchinson, a roof consultant based in Chicago and technical consultant for the EPDM Roofing Association (ERA). He’s been on roofs he’s specified 15 years earlier that are leaking, but fixable. “The membrane itself was in great shape,” he says. “You don’t have to replace the roof. Just repair the seams and replace the base flashing.”

Are “Cool Roofs Required or Encouraged

The U.S Department of Energy Informs us:

In some regions, cool roofs are required by legislation. Voluntary programs may also encourage building owners to pursue cool roofs. For example, irrespective of climate, cool roofs qualify for 1 point under the USGBC’s LEED-NC 2009, Sustainable Sites Credit. When cool roofs are optional yet encouraged, the decision should be considered carefully as cool roofs do not perform equally well everywhere.

More On Energy

EPDM’s outstanding thermal performance and long-lasting durability makes it a viable roofing choice for energy-efficient roof systems in much of the country. In regions where there are more heating degree days than cooling degree days, the energy efficiency of an EPDM roof with proper insulation will likely produce more energy savings than reflective roofs.

In fact, in those regions where cool weather predominates, a dark roof membrane such as standard EPDM will prevent the buildup of condensation within the roof assembly. Because light-colored membranes remain cooler than their dark-colored counterparts, the contrast between warm interior temperatures and the cooler ones outside is much greater. This can often lead to the development of condensation within the roof assembly which is often mistaken for a leak.

Source – http://www.epdmroofs.org/epdm-todays-choice/cool-roofing

Cautions From The U.S. Department of Energy About Cool (White) Roofing

In a report, Guidelines for Selecting Cool Roofs, July 2010, the U.S. Department of Energy makes the following observations:

• Climate has the biggest impact on energy savings.
Cool roofs achieve the greatest cooling savings in
hot climates (Climate Zones 1-3) but can increase
energy costs in colder climates due to reduced
beneficial winter time heat gains.

• When cool roofs are optional yet encouraged, the
decision should be considered carefully as cool
roofs do not perform equally well everywhere.

• The energy cost savings you can realize from a
“cool”(white) depends on many factors, including
where you live.

• Although annual cleaning can restore up to 90% of
initial reflectance, the energy cost savings alone
does not warrant the cost.

• As a cool roof becomes dirty from pollution, foot
traffic, wind-deposited debris, ponded water, and
mold or algae growth, its reflectance will
decrease, leading to higher temperatures.

• There are some important questions about the
durability of cool roof systems in certain applications.

• In colder climates, like Chicago or Alaska (Climate
Zones 5-8), there is less heat available
to dry out the roof and more opportunities for
condensation to occur.

EPDM : Here Today…Here Tomorrow!

Longest Lasting Commercial Roofing Product In The Industry… Bar None

Sus-tain-a-ble [suh-stey-nuh-buhl] adj. Pertaining to a system that maintains its own viability.
Characteristics that contribute to EPDM’s overall system performance include:

• Long-lasting performance

• Flexibilty

• Outstanding weathering characteristics

• Unmatched resistance to ozone, UV radiation and cold cracking

• Dimensionally stable

• Limited environmental impact

• Low life-cycle cost

Longest Average Serviceable life:
As environmentalists and code regulators place more emphasis on the sustainable performance of building materials, EPDM continues to be the commercial roofing material that stands the test of time. 45 years of empirical experience in field applications has shown EPDM to have the commercial roofing industry’s longest average service life, according to the latest study provided by ERA (EPDM Roofing Association). ERA tested installations 28-32 years of age. The study shows that all of the aged EPDM roof samples taken have physical characteristic properties above or just below the ASTM minimum properties required of newly manufactured 45-mil EPDM membrane, and estimated them to exceed 40+ years of serviceable life.

Commercial Roofing Company:Chicago’s Best

A Proven History:

Since 1978 we have installed commercial roofs in Chicago and surrounding suburbs.In 1984, single-ply EPDM roofing membrane began proving itself as an industry leader. Thomas J. Preston Jr., and his son, now owner, Thomas J. Preston III, strategized to develop a flat roof system that will outperform any current commercial roof design. Since then, Thomas III and the Dura-Ply team privately tested the performance of many manufacturers’ materials, assuring the consistency of quality that drives the success of a Dura-Ply commercial roof.  While most commercial roofing contractors in Chicago install many different variations of roof applications, our crew has been trained in this one application, our application, which provides great uniformity in workmanship for the best possible job, done with craftsmanship, that is hard to compare. We are proud of our crew and product.