Modified bitumen (pronounced bitch'-you-men) is a membrane-style roof that can be installed as a one-, two-, or three-ply system, though most are two-ply applications. The roof is generally comprosed of a base sheet, plus two modified ply layers. Each layer is attached to one another and sealed using heated asphalt.
Technically, bitumen is another word for asphalt. Modified bitumen is asphalt that has had modifiers added to it, giving it plastic- or rubber-like properties—things desirable in a roof. Modifiers help to provide more tensile strength and flexibility to the roof, and these qualities are extremely important if the roof is to withstand a building's flexing and moving.
Like single-ply systems, bitumen roofs are manufactured elsewhere, but applied on site. They are assembled on the roof, but manufactured in the factory for quality control.
It is important to cover the top of modified roofs with a protective layer to block out the sun's ultraviolet rays. The roof can be covered with gravel or with a UV reflective granulated surface, with the granulated surface being the lighter of the two. (Homeowners considering a gravel top layer should first be certain that their home can structurally support its weight.)
As in any industry, new solutions are emerging. Although many of the new roofing technologies recently have focused on 'green' roofs, or on those covered all or in part by vegetation and soil, other technologies focus on water repellency.
A curious, recent roofing system discovery is Wetsuit, manufactured by Neptune Coatings, headquartered in Grass Valley. The Wetsuit system is composed of water-based neoprene rubber (yes, the same material used to make wetsuits) and installed in a manner similar to foam applications. The dark-colored waterproof rubber membrane is spray-applied and usually capped with one of a variety of topcoats, including a white elastomeric that meets 'cool roof' standards.
The rubber coating, according to Neptune Coatings, creates a seamless and monolithic system that is waterproof, non-toxic, odorless, free of any solvents or adhesives, and cures almost immediately upon application. The manufacturer even recommends Wetsuit for use beyond rooftop applications—for foundation waterproofing, and for sealing of ponds, fountains, decks, and shower stalls.
After a dozen years of research, Wetsuit came onto the market three years ago, and today has a handful of certified applicators in California. One of them is Arctic Roofing, also based in Grass Valley, whose sales manager, Mark Ostrov, is optimistic about getting behind such a relatively new product.
"We took on Wetsuit as a product line after 20 years in the roofing business because we saw this product being the best solution for satisfying the flat-roof needs, both commercial and residential," Ostrov says.
The next roof on your modern home will be required to have a light-and-bright reflective surface and meet energy-efficient 'cool roof' standards, if the California Energy Commission moves forward to modify the energy laws for residences as it has for commercial buildings.
In an effort to mandate more California residents and businesses to conserve energy, Energy Efficiency Standards for Residential and Nonresidential Buildings, called 'Title 24,' were started in 1978. The standards are updated periodically to allow consideration and possible incorporation of new energy efficiency technologies and methods.
Currently, under Title 24, commercial roofs must have a coating that effectively reflects the sun's energy from the roof surface. It's a standard that may affect residential flat and low-sloped roofs very soon.
These so-called 'cool roofs' are oftentimes bright and white, or at least light enough in color, to reflect heat before it enters a building and directing it back into the environment. By reflecting solar radiation, these roofs also decrease urban heat build-up, raise the area's inversion layer of air, and reduce smog concentrations.
The California Energy Commission is currently considering whether to add reflective requirements to flat and low-sloped residential roofs for 2008, which would be enforced starting in 2009. "If we were really energy conscious," says energy commissioner Art Rosenfeld, "we would apply a regulation to all roofs, including sloped roofs—but we don't have the courage to do that."
While the pending legislation may not impact installers of foam and single-ply systems, which generally meet 'cool roof' standards, installers of other roof systems that are not inherently reflective are adjusting their methods in anticipation of the new requirements.