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www.greenbuildermag.com 08.2012


SOME ASSEMBLY REQUIRED – The Hands-On Handbook Continued from previous page 24 ~ How-to ~ RECYCLE AN ASPHALT ROOF Extending shingle life


As shingles age, they weather naturally, eventually reaching a point of failure —but the pre-failure weathering phase may last for years, during which time the shingles are still sound. You can help extend shingle lifespan by reducing the rate of weathering at the construction/installation phase. Keep the following weathering accelerators in mind.


SHINGLE QUALITY


Low-quality shingles will fail before high-quality shingles. Quality can vary widely among manufacturers, and even within a single manufacturer’s product line.


STRUCTURE ORIENTATION South-facing roof slopes have shorter lifespans due to increased thermal cycling and UV exposure. Some portions of the roof are aff ected by prevailing winds more than others.


DEGREE OF ROOF SLOPE Flatter roofs have shorter lifespans because they shed moisture more slowly and are more directly exposed to UV radiation than roofs with steeper pitches.


CLIMATE Harsh climates shorten roof lifespans. Wind, moisture and thermal cycling all contribute to deterioration of roofi ng materials.


THERMAL CYCLING Climates with large daily temperature swings shorten roof lifespans because they cause greater amounts of expansion and contraction. This increases the roof’s rate of deterioration.


ROOF COLOR Darker roofs absorb more heat, which shortens shingle lifespan by accelerating the loss of volatiles and increasing thermal cycling.


Source: InterNACHI: /www.nachi.org/


ELEVATION Homes at higher elevations are exposed to more UV radiation, which deteriorates most roof-covering materials, including asphalt shingles.


ROOF STRUCTURE VENTILATION Poor ventilation of the roof structure shortens shingle lifespan by failing to keep shingles cool, resulting in accelerated loss of volatiles and greater amounts of thermal cycling.


QUALITY OF MAINTENANCE Failure to repair damage and keep roofs clean can result in damage and deterioration from moisture intrusion and wind.


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