Roof & Wall Coatings
Western Roofing
Insulation and Siding Magazine
March/April, 2000
Lower Energy Costs
Cool Sprayed Polyurethane Foam Roofing Insulating Your Building from High Energy Bills
by Kevin Hansen, Power PR
It’s a hot day in the city. Sweaty office workers are cranking up the air-conditioning in their buildings, trying to stay comfortable. Little do they know that the temperatures up on their roof-tops are nearing 2OOF, as the dark colored, asphalt-based roofing material absorbs the beating solar rays, forcing the air-conditioner units to struggle harder while the electric bill soars. At the same time, invisible ultraviolet (UV) light is slowly baking the roof material, causing loss of flexibility, cracking, shrinking and surface erosion of the water-proofing membrane, which means leaks when the rains arrive later in the year.
But what if the building owners could drastically reduce their facility’s peak cooling demand and water-proof the roof with the same capital expenditure? It’s possible with SPF (sprayed polyurethane foam), a closed-cell roofing and insulation material.
SPF, which reflects solar radiation and releases heat easily, can lower roof temperatures by up to IOO F., thereby decreasing the amount of heat transferred into a building’s interior and reducing demand for cooling. SPF also resists UV decay, solves water tightness issues and can be installed quicker and easier than conventional built-up roofing (BUR).
"Polyurethane roofs, commonly called "cool roofs", can bring cooling savings up to 50% with a peak cooling demand of 10-15%," cites Building Operating Management Magazine, one of the many experts praising SPF roofs for home and industrial applications.
Dr. Dean Kashiwagi of the Del Webb School of Construction at Arizona State University notes in his study on roofing system performance that, "The performance of the ..."
"SPF roof system has not been matched by any verified performance of installed BUR or single ply roofing system in the Southwest United States."
The high R (insulation) factor of urethane foam is one of the chief advantages of SPF roofs over BUR. On hot summer days, it’s not unusual for a BUR roof surface to exceed l8O F. This heat is transferred to the building’s interior via poor insulation or by “thermal shorts,” non-insulated elements on the roof such as fasteners and other conductive materials. The same thing happens in reverse during the cold months, with heat escaping the building through these thermal shorts.
However, as SPF roofs have no seams, gaps, or fasteners, there are no thermal shorts to waste energy, the foam insulates from the outside, making it even more efficient in energy savings. SPF is sprayed to a minimum thickness of (I)inch, with a reflective coating over the SPF to protect the foam from the sun’s UV rays. Typical top-costs include acrylic, polyurethane or silicone, depending upon architectural specifications or existing roof surface requirements.
SPF roofs are also a hot topic with the Environmental Protection Agency’s (EPA)’s new Energy Star Roof Products Program, as cool SPF roofs benefit power companies and the environment by reducing the need for airconditioning energy.
Today's roofs are also protected by the CRRC (Cool Roof Rating Society) who mandates that an inital roof meet their guides of 70% Solar Reflectance and 75% Thermal Emitance."By reducing the amount of energy needed to cool buildings,(these) roof products help to reduce the production of air pollutants," says Rachel S. Schmeltz, Energy Star program manager. Additionally, says Schmeltz, "Such reflective roof products can help reduce the "heat island effect," a phenomenon in which cities can be 2 to 8F warmer then the surrounding countryside.
"Reflective roof products are more energy efficient’ (because they reduce air conditioning use) and thus save building owners and homeowners money on their utility bills-, and reflective roof products are at least as durable as other non-reflective roof products and may actually enhance the lifetime of a roof," according to the EPA.
"Such heat islands occur because many buildings and paved surfaces are designed with dark materials that absorb heat from the sun. This heat is released at night, causing the air temperature to remain high. The resulting elevated temperature leads to an increased demand for air conditioning in buildings, increased fuel use for vehicle air conditioning, increased levels of smog and associated increased levels of heat-related and smog-related health problems. Installing reflective roofs helps reduce the heat island effect, decreasing the amount of smog in the air and benefiting the entire community."
The success of spray-applied SPF roofing is partly attributable to manufacturers such as SWD Urethane Company of Mesa, Az., a leading expert in polyurethane foam systems, specialty coatings, and polyols. The company’s state-of-the-art production facility provides the highest quality assurance standards in urethane foam systems for roofing and insulation.
Ari-thane Foam Product, Inc., general manager, praises SPF for its high insulation factor, monolithic (seamless) covering and light weight. "You spray it over an existing roof without doing a tear-off in most cases. This is great because it saves labor and risk." He describes the SPF application process, "First we apply a primer, then the foam. It is in the liquid form in two parts, which is pumped through several hundred feet of heated, insulated hose. The two components mix at the tip of the spray gun in an exothermic (heat-generating) reaction and the compound is sprayed out onto the roof in a liquid. It raises in about 15 seconds, and after about a minute you can walk on it; it’s that quick. If the ambient temperatures are hot, the set-tip time is even faster. We generally lift hoses, wires or machinery on the roof and spray under them, then set them back down on wood blocks."
Dr. Rene Dupuis, Ph.D. PE of Structural Research Center, Inc., at a National Roofing Contractors Association convention said "based on his initial findings of jointly sponsored study of SPF roofing systems, SPF may be one of the most sustainable roofing systems to date."
For applicators, SPF roofing’s case of installation is unparalleled. The foam can be sprayed directly over built-up roofing (BUR), modified bitumen, concrete, wood and metal roofs, often without the need to remove the original roofing, reducing time, labor, materials, expenses and waste. SPF forms a continuous air barrier, preventing moisture infiltration caused by air leakage and minimizes condensation within the structure. By controlling moisture infiltration, SPF also prevents moisture within the building envelope, the number one cause of building deterioration. Such advantages are inspiring great interest among roofers still using traditional methods.
While SPF may be slightly more expensive up front, the material’s longevity means cost-effective operations and proven lifecycle costing benefits. Commercial or residential foam roofing systems typically require only minor maintenance over many years and may be renewable with simple re-coats.
One end-user who realized the significant insulation benefits of SPF is Pacific Equities in Chandler, Az.. The property management company installed foam roofing on 21 buildings, covering over 280,000 square feet of roofing in one of the nation’s hottest climates.
"Most of the buildings we own are multi-tenant light-industrial, about 20% office and 80% warehouse," says John Brownlee, the company’s regional manager. "The roofing has withstood the severe heat without problems and given us a little insulation as well. Many people commented that, ‘the roofing knocked 10 to 15F off the heat in their warehouse, for which they were very happy.’ We also liked the price, as well as the high R factor ... it was more economical than the conventional roofing options we examined," continues Brownlee.
Also plagued by heat problems, Mark McClure in Orange, Calif., decided to install ail SPF roof on an uninsulated steel building housing the paint shop at his previous workplace. "I was working for the Sargent Fletcher Company, an aerospace form in El Monte. They has a 30-year old paint shop in a galvanized steel building, which has insulation problems," McClure explains. "The building would get so hot that the paint would dry before it could get to the product. In the winter, the cold would have the same effect. There were some swamp coolers on the roof but the heat was too much for them and the building was too porous to stay cool. We didn’t even look at traditional roofing; there was nothing else which would have worked."
McClure needed to control the shop’s interior temperature; otherwise, he would have had to tear down and rebuild the shop or upgrade the heaters and coolers, very expensive options. He decided to try SPF roofing after reading an article about the foam. Rated the highest R value of any insulation material and able to adhere to most surfaces, SPF was ideal for the metal paint shop roof
"We put an inch of foam with a top-coat on the shop roof, and the net result as a drop 8 to 10 F in the building. We never have to shut down in summer or winter again," McClure asserts.