Tag Archives: TPO

TPO on Top: Why the Roofing Material Continues to Shine

by Mike Mendoza

Thermoplastic polyolefin (TPO) is a relatively new material, but makes up one of the fastest-growing sectors of the commercial roofing industry.  All images courtesy Firestone Building Products

Thermoplastic polyolefin (TPO) is a relatively new material, but makes up one of the fastest-growing sectors of the commercial roofing industry. All images courtesy Firestone Building Products

As building codes and environmental trends continue to evolve, so too does the diversity of roofing material options. These factors, along with others, make construction specifiers’ roofing installation and selection prowess of utmost importance.

Among the available choices is thermoplastic polyolefin (TPO). Despite the fact this technology is fairly new in the scheme of roof materials, it makes up one of the fastest-growing sectors of the commercial roofing industry. That growth brings with it constant improvements to the chemical composition of the membrane to achieve greater durability and longevity.

Nevertheless, representatives for the Single Ply Roofing Industry (SPRI) still point to early 1990s TPO installations that continue to perform thanks to proper installation and maintenance. SPRI data indicates about 371.6 million m2 (4 billion sf) of TPO was installed in North America between 2005 and 2010, with nearly the entirety still performing without issue.1

“We at SPRI are confident TPO roofing systems will continue to provide quality and value for many years to come,” said the association’s technical director, Mike Ennis.

Indeed, a 2013 study that used ASTM D6878, Standard Specification for Thermoplastic Polyolefin-based Sheet Roofing (revised to address concerns of prolonged exposure in extreme heat climates) shows the material’s durability.2

“The heat aging exposure at (116 C [240 F]) was extended from 670 hours to 5400 hours (32 weeks),” the study states. “To meet these new requirements, it is critical for TPO roofing formulations to contain high-quality resins combined with tailored stabilization, flame retardants, and membrane design.”

Results showed TPO roofing membranes produced using the right polymer formation and stabilization can perform in some of the most extreme climate conditions: “Depending on the climate zone, 1.5-mm (60-mil) membranes may last up to 25 years or more.”

Beyond durability, TPO single-ply roofing membranes offer several other performance and installation advantages. These assemblies can provide resistance to ultraviolet (UV) rays, ozone, and chemical exposure. Further, the reflective surface meets the U.S. Environmental Protection Agency’s (EPA’s) Energy Star requirements, and is both recyclable and composed of recycled content.

Knowing the options
Settling on the ideal TPO roofing system relies on identifying and analyzing the characteristics surrounding climate and condition of a commercial building’s existing roof surface. Factors include:
● potential for tears and abrasions;
● area wind speeds;
● UV exposure; and
● various surfaces (e.g. vertical parapet walls) and slopes.

When it comes to color choice, white is among the most popular option for reasons discussed later in this article. However, it is not the sole TPO variety to consider, particularly if another hue better suits a rooftop. In addition to white, TPO membranes often come in gray and tan.

Since TPO membranes are installed fully-adhered, ballasted, or mechanically fastened, they work with a range of building envelope designs, offering architects flexibility. Architects most commonly select TPO roofing for flat or low-slope installations because of its cost-effectiveness, easy installation, and heat-welded seams that prevent moisture penetration.

Keeping cool
A specific driving factor for choosing TPO is within the realm of cool roofing. The Cool Roof Rating Council (CRRC) was created in 1998 to “develop accurate and credible methods for evaluating and labeling the solar reflectance and thermal emittance of roofing products,” according to the nonprofit organizatioRoof Surface Properties (CRRC)n’s history and bylaws. In the 15 years or so since, a lot of roofing products now come in what can be considered ‘cool’ varieties.3 Field-applied coatings, single-plies, tiles, and others fit this bill, which the council defines as a surface that reflects and emits the sun’s heat back into the sky rather than transferring it to a building.

A roof’s solar reflectivity and thermal emittance (the ability to release absorbed heat), are both measurable factors, according to the U.S. Green Building Council (USGBC). The Green Building Alliance, a chapter serving the Greater Pittsburgh, Laurel Highlands, and Northwest Pennsylvania branches, says as many as 90 percent of roofs in the United States are, “poorly designed and built with dark, non-reflective heat-absorbing materials,” causing rooftop temperatures to hover as many as 50 C (90 F) above that of the air.

The more reflective a TPO surface, the more likely it will comply with increasingly stringent building codes. Therefore, white TPO membranes—the most reflective—can be a suitable choice for those striving for maximum energy savings and environmental benefits.

The U.S. Department of Energy (DOE) touches on this concept in its 2010 study entitled, “Guidelines for Selecting Cool Roofs,” stating a conventional dark-colored surface reflects about 20 percent of incoming sunlight while a “cool” light-colored one (white being the lightest) reflects as much as 80 percent.4

EPA goes one step further in its “Reducing Urban Heat Islands: Compendium of Strategies” focusing on cool roofs. The report uses a diagram from the Lawrence Berkeley National Laboratory (LBNL) to compare the solar reflectance of black, metal, and white roofs.5

Roof Reflectance, EmittanceOn a hot, sunny summer day, a black roof that reflects five percent of the sun’s energy and emits more than 90 percent of the heat it absorbs can reach 82 C (180 F). A metal roof will reflect most of the sun’s energy while releasing about a fourth of the heat it absorbs; it can warm to 70 C (160 F). A cool roof will reflect and emit the majority of the sun’s energy and reach a peak temperature of 48 C (120 F).

CRRC lists white, tan, and gray TPO roofs among its ‘environmentally friendly’ options, and white and tan are compliant with California’s Title 24 Energy Efficiency Building Standards. Cool roof requirements have been adopted in several U.S. building energy codes, and an increasing percentage of electric utilities have begun offering rebates for cool roofing materials, including TPO, that help conserve energy and reduce buildings’ environmental impacts.

According to USGBC, TPO and other cool roof options yield the following benefits:
● utility rebate opportunities;
● lower indoor temperatures;
● reduced maintenance costs (partially due to the material’s longer lifespans);
● improved air quality resulting from a reduction of emissions such as mono-nitrogen oxides and carbon dioxides in the atmosphere;
● mitigated heat island indexes (i.e. less heat creation in dense, urban areas); and
● reduced energy bills because less air-conditioning is needed during the summer.

Conclusion
Not unlike other roofing product manufacturers, those offering TPO will recommend consulting a design professional to ensure proper roofing system selection, conformance to building codes, and insurance requirements. Such customizations further emphasize evaluating a roof’s current condition is paramount when determining how best to repair or replace it. Further with ever-changing code and material options available, it is important for construction professionals to remain educated about the changing commercial building products landscape.

Of course, amidst the increasingly popular cool roofing and TPO possibilities, it is crucial to be cognizant of the fact roofing materials are not the sole remedy to increase overall building performance. It takes a holistic approach to have a building perform at peak efficiency.

This fact emphasizes the importance of building products manufacturers working closely with architects and construction specifiers—as well as consultants, contractors, facility operators, and building owners—who share similar goals of increasing overall building performance.

Together, these professionals should consider the entire building envelope to continue revolutionizing the commercial building industry, yielding an impact that reaches far beyond their individual buildings, cities, and immediate populations.

Notes
1 Visit www.spri.org/pdf/spri_responds_to_pro_roofing_article_on_tpo.pdf. (back to article)
2 Visit msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_08e0/0901b803808e057f.pdf. (back to article)
3 See the council’s “Reducing Urban Heat Islands: Compendium of Strategies” by visiting www.epa.gov/hiri/resources/pdf/CoolRoofsCompendium.pdf. (back to article)
4 The DOE study can be found at www1.eere.energy.gov/femp/pdfs/coolroofguide.pdf. (back to article)
5 See S.L. Konopacki et al’s 1998 report, “Demonstration of Energy Savings of Cool Roofs,” also known as LBNL-40673. (back to article)

Mike MendozaMike Mendoza is the thermoplastic polyolefin (TPO) product manager for Firestone Building Products. He is responsible for researching market trends and directing the planning and development of thermoplastic products. Mendoza previously spent 13 years at Owens Corning where he served in various roles including as a southwest region sales manager for roofing, strategic product planning manager for asphalt, and director of global sourcing for insulation. He can be reached at mendozamichael@fsdp.com.

Industrial Daylighting

Increasing light quality and reducing energy load

All images courtesy Acuity Brands

By Brian Grohe

For an electrical conduit design and manufacturing company in Roselle, Illinois, a new plant would represent as much as a 60 percent increase in company production and 25 new jobs in the community. However, before expanding manufacturing operations to a 4923-m2 (53,000-sf) space, there needed to be major changes to the 14-year-old building.

The building would be reclassified from industrial to heavy manufacturing, and it would be made as environmentally sound as possible. This meant improved energy efficiency where it was most achievable—in the building’s thermal properties and lighting system. Specifically, the company wanted vegetated roofing assemblies, lowered indoor temperatures, and improved energy efficiency, as well as daylighting solutions.

Two years ago in another project, 15 skylights were retrofitted with new ones from a California-based manufacturer specializing in high-performance prismatic skylights for the commercial market. Having seen the enhanced performance of those skylights, project manager Ed Berbeka opted for them again.

This photo shows the 55 to 62 footcandle (fc) readings inside the facility after the installation of prismatic skylights.

This photo shows the 55 to 62 footcandle (fc) readings inside the facility after the installation of prismatic skylights.

A total of 56 skylights were installed in the Roselle facility last October, at the same time the insulation and new roofing was installed. For the insulation upgrade, R-25 insulation would meet the latest international standards for long-term, thermal-resistance values. For the roofing upgrade, the existing ethylene propylene diene monomer (EPDM) black membrane was replaced with more reflective white—and more energy-efficient—thermoplastic polyolefin (TPO) material. The TPO assembly, lightweight and time-tested since the mid-1970s, reflects the sun’s rays to reduce incoming heat, and does not require rock ballast.

New electrical and energy-efficient lighting was also part of the upgrade to the building. After the roof renovation, the building’s interior temperature decreased by an estimated 17 C (30 F)—a measure taken during the month of August, just before the entire project was completed.

Lighting also significantly improved. The new skylights cover three percent of the roof area, which is relatively standard for industrial buildings. Thanks to their prismatic properties, however, the lighting inside the building, which has a ceiling height of about 12.19 m (40 ft), is anything but standard.

Generally speaking, warehouse lighting varies from as few as 5- to 10-fc (footcandles) in inactive storage areas, to as much as 30- to 40-fc output in more active spaces such as loading docks or receiving areas. After the installation of the skylights, light-level readings in the building reached from 55 to as much as 62 fc—without any use of electrical lighting.

A new roofing membrane and insulation to reduce the HVAC load were installed.

A new roofing membrane and insulation to reduce the HVAC load were installed.

The electrician took note of the lack of ‘hot spots’ created by typical bubble-dome skylights, which can allow heat to build in the space below. The specified skylights, however, diffuse the incoming light through its prismatic lenses, eliminating hot spots, glare, or haze, as well as dissipating any heat. All that remains in the space is fully captured, evenly distributed and ultraviolet (UV)-stable daylighting coverage.

In addition to increasing the interior light source and providing increased energy savings, the building owner says the daylighting solution also boosted employee morale in the manufacturing plant.

Brian Grohe, LEED AP, is the corporate accounts manager–industrial for Acuity Brands. He holds a bachelor’s degree from Columbia College in Chicago. With more than nine years in the daylighting industry, Grohe has held roles in regional sales and business development. He can be contacted by e-mail at brian.grohe@acuitybrands.com.