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Friday, August 20, 2010

Aging Asphalt Compostion Roofing

When a roof gets hot the asphalt experiences an increase in aging or accelerated aging. Asphalt is an organic product produced from crude oil. After all the solvents, gas, turpentine, jet fuel, and other products are removed what is left is asphalt. Heating asphalt cracks or flashes off the lighter oils still left that give it its resilience or ductility.
The testing method I remember from years ago, ASTM D-312, which is probably still in use, was used to determine ductility, penetration, and other qualities. The NRCA states:
ASTM D312, "Standard Specification for Asphalt Used in Roofing," defines four types of asphalt intended for use as a waterproofing agent and/or adhesive in roof system construction. Type I, Type II, Type III and Type IV classifications correspond to roofing asphalts characterized by increasing softening points. (A higher softening point indicates resistance to flow at higher temperatures.) In built-up roof membrane construction, Type III or Type IV asphalt is used; the choice depends on membrane slope. Roofing asphalt is a product of crude oil refining and should not be confused with coal-tar pitch, also used in roofing, which is derived from coal distillation. Although both are types of bitumen, asphalt and coal-tar pitch are not compatible.

That is primarily used for built up roofs and there's a gob of ASTM D-something for asphaltic product standards but the one for shingles is:

ASTM D3462, "Standard Specification for Asphalt Shingles Made from Glass Felt and Surfaced with Mineral Granules," addresses properties of asphalt feedstock, shingle material composition, dimensional tolerances and weights, fire test classification, wind resistance, loss of volatile matter after heating and other physical properties of finished materials. Self-sealing shingles, as well as interlocking shingles, are included in the standard's scope.

Fresh shingles are gooey in the sun because the asphalt has not oxidized. Fresh asphalt is a frozen liquid during nice temperatures and as it oxidizes over time, coupled with the flash off of volatiles, becomes a true solid.

Remember how the fresh tar (asphalt) gummed up your tires and then picked up pebbles? Later the asphalt turned gray and brittle. The smell was gone too. That process took a while but with all the engineering put into modern composition roofing it takes years. Additives, particles, different types of stabilizers and new improved fiberglass mats have increased the roof life in Dallas from 12 years on the old organic paper based roofing to up to 50 years with the new products.

The new ceramic granules also help to slow ultra violet degradation better than the old granite chips. Nothing helps when the shingles are scuffed by roofers working during hot temperatures and not using foam pad roof protection. You can see foot prints and read the brand names sometimes.

If the ventilation is improper the aging speeds up. The roof and deck experience more heat and humidity and the rate of decay is accelerated by as much as three or four times. In other words the thirty year material can look bad in as little as seven years.

The south and west slopes age faster in the northern hemisphere where we perform most of our roof projects. In those remote locations where the north slope is baked first it is usually hotter in January than July.

Ventilation, not venting, is the key to a long happy roof. Such a roof not only looks good longer, it is more hail resistant and less prone to leak. Plus the inhabitants of the abode are happier and healthier and have more disposabile income.

Steep roofs tend to last longer too as they dry off faster and suffer less air born fungus and slime mold, that streaking on the roof that disappears beneath the stacks, chimneys, and skylights because of the zinc coming off the galvanized metal and solder. Zinc is an antimicrobial and has been added to many shingles for this purpose. Copper is also being used in the shingles to keep them healthy, happy, and wise.

This week we did two homes with new radiant barrier decking by Techshield and the customers are ecstatic. One was in Plano and the other in Irving. Ryan found a faux soffit vent on the Plano home, a first for Jon Wright Roofing. We've seen very small holes but never no hole.

That carpenter is such a criminal. That lady had such a hot attic but now she doesn't. She didn't have to replace her deck but she was half way there so she crossed the finish line. With her class IV roofing I bet she saves $10,000.00 over the next ten years on utilities, insurance premiums, HVAC repairs, and preventing hail damage.

Anyway, we all have our own asphalts to work on so lets make the world a better place, at least in Dallas, Plano, Irving, Grand Prairie, Fort Worth, and Carrollton. Forget about Australia. They talk funny and have a queen. They have an election today though. I just learned their Liberal Party is the conservative one. Just like a place where January is hot, it's dark when it's light here, the potty water swirls backwards, and they name all their women Sheila.


1 comment:

Liquid Rubber said...

Your post is little bit lengthy but its interesting about asphalt many people did not know that the thing they are using from which material they are made so your post give them a lot of information.