Page 26 - Green Builder Homeowner's Handbook 2016

The Homeowner’s Handbook SEVENTH EDITION

Life Expectancy of materials may contain components such as metal fasteners and ad-
Roofing Materials hesives, thereby rendering those portions unusable for new roofing
products.
Asphalt 20+ years
In addition, these plastic products have not been in the market
Fiber Cement 25 years long enough for homeowners to know how stable they are, how well
they hold up to UV light degradation and what kind of expansion-
Wood 25 - 30 years contraction issues may occur over time.

Slate 50+ years CEMENT COMPOSITES
Lower Life-Cycle Costs
Simulated Slate 10 - 50 years*
Also scoring high in the recycled content category are cement com-
posite roofing materials, such as fiber-cement shingles, which offer
good durability. However, the sustainability of cement composites
depends on the source of feedstocks used for production and, more
importantly, the source of energy used to create the cement.

Fiber-cement products have high embodied energy as well. In
response, some companies use fillers like wood fibers or fly ash
to reduce the required amounts of cement, concrete and aggregate
material. Another side benefit is these filler materials create tiles
and shingles, which weigh significantly less than standard concrete
roofing products and therefore require less energy to transport.

However some fiber-cement roofing shingle products were discon-
tinued after beginning to fail from swelling, cracking, shrinking or
discoloration within five years.
Metal 40 - 80 years SOURCE: NAHB AND INTERNACHI
PHOTO COURTESY: INTERGCONGREEN.COM
Clay/Cement Lifetime

Copper Lifetime

*The two sources reported large differences on the longevity of this material.

Mitigating Factors. The actual lifespan of roofing materials
depends on original quality, installation, maintenance, climate
and other factors.

Sustainable Spectrum: Low-Slope Roofing

W HAT IS THE MOST ECO-FRIENDLY OPTION
FOR FLAT ROOFS? The durable synthetic
rubber membrane known as EPDM (ethylene

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

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.”

24 GREEN BUILDER The Homeowner’s Handbook 2016 www.greenbuildermedia.com