Page 20 - The Homeowner's Handbook 2017

THE HOMEOWNER’S HANDBOOK EIGHTH EDITION

Life Expectancy of materials may contain components such as metal fasteners and ad-
hesives, thereby rendering those portions unusable for new roofing
Roofing Materials products.
In addition, these plastic products have not been in the market
long enough for homeowners to know how stable they are, how well
Asphalt 20+ years
they hold up to UV light degradation and what kind of expansion-
contraction issues may occur over time.
Fiber Cement 25 years
CEMENT COMPOSITES
Wood 25 - 30 years
Lower Life-Cycle Costs
Also scoring high in the recycled content category are cement com-
Slate 50+ years
posite roofing materials, such as fiber-cement shingles, which offer
good durability. However, the sustainability of cement composites
Simulated Slate 10 - 50 years*
depends on the source of feedstocks used for production and, more
SOURCE: NAHB AND INTERNACHI to reduce the required amounts of cement, concrete and aggregate
Metal 40 - 80 years importantly, the source of energy used to create the cement.
Fiber-cement products have high embodied energy as well. In
Clay/Cement Lifetime response, some companies use fillers like wood fibers or fly ash

Copper Lifetime material. Another side benefit is these filler materials create tiles
and shingles, which weigh significantly less than standard concrete
*The two sources reported large differences on the longevity of this material. roofing products and therefore require less energy to transport.
However some fiber-cement roofing shingle products were discon-
Mitigating Factors. The actual lifespan of roofing materials tinued after beginning to fail from swelling, cracking, shrinking or
depends on original quality, installation, maintenance, climate
and other factors. discoloration within five years.

Sustainable Spectrum: Low-Slope Roofing

HAT IS THE MOST ECO-FRIENDLY OPTION
FOR FLAT ROOFS? The durable synthetic
rubber membrane known as EPDM (ethylene
W propylene diene monomer)—with its low
installed cost—continues to be a popular choice. However, as
a petroleum-based product with a fairly short service life, it is
not all that sustainable.
Responding to the market demand for sustainable products,
some manufacturers have begun offering “cool” EPDM in
white, to decrease unwanted heat gain to the interior, extend
the membrane’s life and help mitigate the heat island effect.
Otherwise, a protected membrane roofing assembly
enhances durability for low-slope roofing and could therefore PHOTO COURTESY: INTERGCONGREEN.COM
be considered sustainable, says Christopher Dixon senior
associate/architect and specifier at NBBJ in Seattle.
“Thermoplastic polyolefin (TPO) membrane roofing materials
are popular today and have recently replaced PVC as the A Growing Trend. The green roof topping Armstrong Atlantic
most common thermoplastic membrane material,” adds State University’s Learning Commons absorbs rainfall and
Mark Yanowitz, principal and licensed construction designer reduces stormwater runoff.
at Verdeco Designs in Andover, Mass. “They are generally the product quality and proper installation, so do your research.
preferred over PVC, as they are considered a ‘cleaner’ polymer, At the same time, Yanowitz suggests that the leading
containing less problematic additives than their PVC equivalent. sustainable strategy for flat roofs is integrating a green planted
All thermoplastic membranes are recyclable, but to date, the roof. “Along with protecting the roofing membrane below, these
local and national secondary markets are not well established.” systems can greatly assist in the building insulation and in the
TPO is white (and therefore, cool), but longevity depends on reduction of stormwater runoff.”

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