I have fielded quite a few questions about sustainable technologies and how they can be incorporated into roofing applications. Questions like: What is sustainability? How can I apply it to my roofing system? Is being green the same as being sustainable? There are many ways to incorporate sustainable technologies into steep and low-sloped roofing installations, but I am focusing this column on low-slope roofing applications with sustainable technology.
Sustainability can mean different things to different people. Ralph Velasquez, Director, Sustainable Technologies Group at Tremco Inc. and editor and columnist for www.greenroofs.com, illustrates how difficult it can be to determine sustainability. He asked, “Do you want to measure where the stuff was originally pulled from the earth? How it was it mined or grown? How it was transported? Manufactured? Packaged? How much energy was used in any or all of these processes? How long it lasts? Does it impact the environment during installation or its use? Longevity? How it is handled at the end of its useful life? Does it go to a landfill? Will it be recycled? How much energy does it take to recycle, more then if we produced new goods?” He also went as far to say, “I would contend that any improvement in any one of these areas could be considered sustainable,” while acknowledging that others might disagree. He added, “any progress is better than no action.”
Utilizing sustainable practices in roofing applications can be a vast discussion as well, but for the sake of time let’s narrow this discussion and touch on four main sustainable technologies/practices that are becoming more mainstream in the roofing industry: solar energy, rooftop gardens (vegetative roofs), reflectivity (cool roofs) and recyclability at the end of the service life. Then we can discuss why PVC roofing membranes should be considered to be used with these technologies and other criteria that are needed to choose the correct roofing materials.
Solar EnergySolar technology has come along ways since the 70s when it was mainly confined to aiding in the cost of heating water. Solar photovoltaic (PV) or building integrated photovoltaic (BIPV) panel technology has been developed for installation in conjunction with various building materials including flat and low-sloped roofs. Solar energy systems are sustainable because they use the most renewable resource on the planet, the sun, to generate electricity, providing financial relief from escalating utility costs for as long as the system lasts. Today’s solar technology can be used in any region where there is sunlight and is not reliant on hot climates to generate this power.
Renewable energy technology is big business. In fact, in 2007 the American Solar Energy Society published the Green-Collar Jobs report, which showed that renewable energy and energy efficiency sectors generate 8.5 million jobs and nearly $1 trillion in annual revenue in the United States.
Until recently, solar roofing technologies were too expensive to be a viable roof solution, but with local, state and federal tax incentives, BIPV solar roof technologies have become a promising option. BIPV panel systems have become popular among builders and architects to be used in roofing applications for good reasons. They are installed with few or no penetrations in the roof and their electricity production is more consistent throughout the day than some other solar generating technologies. They are lightweight, durable and flexible enough to be compatible with various roof contours. The European Photovoltaic Industry Association (EPIA) has stated that by 2020, PV will become a global source of energy capable of contributing to the global electricity demand, and by 2040 it could represent 25 percent of global electricity consumption. Most BIPV systems are designed to last between 25 and 30 years. Durability of a roof system to last at least this long is a key factor in a successful solar roof project.
Vegetative RoofsVegetative, garden, or green roofs are sustainable not by generating power but by reducing power consumption, other pollutants, and the urban heat island effect. These systems also result in the following:
• Reduction of storm water runoff, which in turn reduces the stress on urban sewer systems and decreases runoff-related pollution of natural waterways.
• Increased thermal resistance (R-value), which reduces energy costs for building owners.
• Improved air quality. Lower rooftop temperatures mean less smog from the urban heat island effect. Plant life can absorb pollutants as well as carbon dioxide, returning oxygen into the air.
• Reduction of noise pollution. Studies show noise levels in a building can be reduced by as much as 40 decibels.
• Extended life of the roof system. Vegetative systems moderate temperature swings that cause a roof system to expand and contract. They also protect the roof from everyday wear and tear.
In some instances, garden roofs allow developers to maximize the building size by reaching the required green space necessary for local codes by transferring the green space from the ground to the roof.
SPRI, the association representing sheet membrane and component suppliers to the commercial roofing industry, is one organization that is taking this segment seriously by committing time and resources to develop standards and testing for vegetative roofs, including root barrier testing methods and fire and wind standards. When these protocols are put in place, it will benefit contractors with geographic assembly guidelines and building owners with consistent standards to judge roof estimates.
From a roofing standpoint, there are many things to keep in mind when designing a vegetative roof. Will the roofing membrane be impenetrable to strong root systems? How will repairs be done if a leak occurs? What costs would be associated with removing the soil and plants and then replacing them?
In the 2007 edition of the NRCA Green Roof Systems Manual, the following roofing membrane recommendations are given: PVC, hot-fluid-applied polymer-modified asphalt, APP and SBS modified bitumen, EPDM, and one- and two-component fluid-applied elastomeric membranes.
The manual also states, “NRCA recognizes other waterproofing membrane types may be used as part of a green (vegetative) roof system; however, NRCA recommends the use of only the membranes listed above for green roof systems.” Again, durability of the roof system is a key determinant in the success of any vegetative roof project.
Reflectivity/Cool RoofsAccording to the U.S. Environmental Protection Agency (EPA), “Americans spend about $40 billion annually to air condition buildings - one-sixth of all electricity generated in this country.” The agency asserts that using ENERGY STAR-rated reflective roof products can help reduce the amount of air conditioning needed and can reduce peak cooling demand by 10 percent to 15 percent. Reflective roofing materials achieve this result by using white tint or other reflective pigments to reduce the amount of the sun’s radiation (heat) from being absorbed into the building. Reflective colors also help reduce the urban heat island effect.
Some states have adopted reflective requirements into their building codes, mandating minimum reflective roofing. Compliant roofing manufactures have modified their products to meet these new codes. However, since roof systems get dirty and this can reduce reflectivity, additional steps may be needed to maximize what roofing materials can achieve either by membrane enhancement during manufacturing, periodically washing the roof, or both.
If a reflective or cool roof is desired, roofing professionals can turn to organizations such as the CRRC (Cool Roof Rating Council) at www.coolroofs.org and find a list of roofing products with their initial and three-year reflectivity and emissivity values. This allows users to compare products to determine which will best meet their customers’ expectations.
Some PVC manufacturers apply a top finish on their membranes during manufacturing to help keep them cleaner longer, which keeps the reflectivity of the sheet higher than it otherwise might be.
You may ask how recyclability can be considered a sustainable technology. A statement by the EPA stated that construction and demolition waste totals an estimated 136 million tons per year. Today’s recycling improvements allow more and more post-consumer materials, including roofing materials to be processed into other high-end, useful products. Developing reclamation programs and enhancements in recycling technology can greatly reduce landfill waste and reduce raw material consumption. I believe that qualifies recyclability as a sustainable technology. Some roofing manufactures have reclamation programs for their material after their service life is over. This can be a great selling point to an environmentally conscious customer.
Determining FactorsWith all of these exciting sustainable “add-ons” to our roofing systems, it is important to remember that the roof is still a roof, and it needs to keep the structure dry or it fails.
A few key points to consider are listed below:
• Durability - Make sure that the roofing material that is chosen has a documented track record that shows it will lasts as long as the sustainable roofing system is guaranteed for. As a case in point, think of the labor and cost associated with a roofing system that fails in the middle of the life span of a solar energy project. All electrical connections would have to be disconnected, all the panels would have to be removed, a new roof system would have to be installed, and then the solar panels would have to be re-installed and the electrical connections made. The cost would be staggering and could possibly erase any cost savings achieved by the solar system.
A well-designed vegetative roof system may last 40 to 50 years. Open exposure to the elements is an enemy to any roof system. By covering up the roofing system, the garden elements protect it from ultraviolet (UV) rays, heat, thermal expansion and contraction forces, and mechanical damage such as is experienced from hail, wind or foot traffic. This can greatly extend the life of any roofing material. However, keep in mind that some roofing materials do not perform well in ponding water situations and may not be impervious to strong plant root systems.
Durability is crucial for the success of a solar or vegetative roof. PVC roofing membranes are among those up to the durability task and fit perfectly with the sustainable technologies that were discussed above. PVCs have a long documented history of durability and a real world track record to back it up.
• Recyclability - No roofing material will last forever, and someday it will need to be disposed of either by recycling, in a landfill or incineration. If recycling is important to your customer, you may consider looking at manufacturers who have a reclamation program to aid in recycling of the roofing material when its life cycle has ended. The PVC industry is one that has had an established recycling system in place for well over a decade.
Although sustainable technologies have many positive attributes to offer, there are significant building costs associated with them. Contractors and building owners who have an opportunity to incorporate sustainable technologies into the roof assembly must consider many criteria besides initial roofing membrane cost during the design phase. Questions to consider include:
• How long has the roofing material been manufactured?
• Is there any documented proof of roof system life expectancy?
• Is the warranty associated with the material pro-rated?
• Are there additional project-specific criteria based on the sustainable technology?
Keep in mind that an unproven material may end up costing you and the building owner much more than the cost of choosing a slightly more expensive material that has a well-known or documented track record and proven warranty.
Although there are other roofing materials sufficient to uphold these sustainable technologies, PVCs have all the proven criteria needed to be among the best choices of roofing materials for building owners and contractors and look to have a bright future in this upcoming segment of the roofing market.