When we think about sustainability in roofing, images of LEED certification requirements and environmentally friendly roofing materials are often the first to come to mind. We think of “green products” and “green certifications.” But is that truly all that defines how environmentally friendly our construction choices are?
Yes, sustainable building practices depend on making responsible material choices. But sustainability is also about the longevity of the roofing system (staying out of a landfill) and the total life cycle impact of that roof. It’s also about how the roof contributes to environmental factors within the building and outside of it.
If we are to make environmentally conscious roofing choices, we need to broaden our definition of sustainable beyond the obvious. Sustainability isn’t just about whether or not a decision earns us green building credits, but rather about both short- and long-term environmental impacts of those decisions.
If you’re planning to invest in strong roofing systems that not only withstand the elements, but also won’t negatively impact the environment, there are a variety of factors you should be considering during the design and material selection phase. In this article, we will walk through four of those factors and how they are relevant from a sustainability standpoint.
What Goes Into a Truly Sustainable Roofing Design?
Let’s start with the obvious contributing factor to sustainable design: the actual materials used to construct the roof. Materials range in eco-friendliness depending on their propensity to emit VOCs during use, the renewability of the resources used to construct them, the way in which they are manufactured and a number of other composition-related factors. There are plenty of products out there that contribute points toward LEED certification, and walking through those would be a great place to start your research.
Keep an eye on advancements taking place in the realm of material composition, too, as innovative products are being developed to help make sustainable roofing more of a reality. Take, for instance, a waterproofing system which replaces a portion of the asphalt used in modified roofing systems with canola oil. Not only is canola oil a renewable resource with minimal environmental impact when deposited in a landfill after a roofing tear-off, it provides strong multi-ply protection as well as elevated UV resistance to fight weathering. Products like this are especially compelling from a sustainability standpoint, but there are many options available to you.
Roofing System Longevity
Roofing material choice matters not only from a product composition perspective, but based on its ability to withstand the test of time too. When taking a long-term view of a roofing project, it’s important to realize that tear-offs at the end of the roof’s life span contribute a substantial amount of waste to landfills, creating a negative environmental impact many overlook. The longer a roof lasts, the less cumulative waste is being contributed to those landfills.
When choosing roofing materials and constructions, making an investment in longer-lasting systems, such as redundant, multi-ply constructions—or at least decently durable single-ply systems—can drastically reduce tear-off waste. Whereas a single-ply system might last 10, 15 or maybe 20 years, a multi-ply SBS-modified bitumen system can last 25 years or more with proper maintenance. The difference between installing a 15-year roof versus a 25-year roof adds up to a huge difference in landfill waste when that difference is multiplied across installations.
These multi-ply systems can also be coated with materials designed to renew and extend the life span of the roof for several more years. SOPREMA ALSAN Coatings, for instance, are used to turn “good” roofing performance into “great,” keeping them in service longer. An added benefit of these coatings is protection against UV weathering and increased reflectivity, not just extending the waterproofing performance.
Longer roof life spans don’t just mean less labor and cost long term; they mean making a real dent in a major industry waste issue. Remember that it’s not just material choice that affects roofing life spans, training and quality of application are huge players too. The best roofing materials in the world won’t last if they aren’t well installed!
Energy Consumption Impact
Another angle to consider is how roofing construction impacts the environment within your building. Heat buildup on a rooftop not only contributes to urban heat island effects along with other surrounding dark surfaces, but can drive up energy consumption within a building when HVAC units run longer and harder than they would otherwise need to.
One way to combat this is to consider reflective roofing materials or coatings. Products like bright white granulated roofing material, for instance, can reduce energy costs by anywhere from 10 to 50 percent by reflecting the sun’s light instead of absorbing it. Vegetated roofing constructions can also help, not only by soaking up sunlight, but by adding additional insulation to the building through soil and root layers. In either case, UV aging can also be reduced when sunlight is kept off the waterproofing layer.
When considering what materials might make sense to reduce your HVAC-related energy costs, look at both reflectivity and “emissivity,” which speak to a material’s effectiveness emitting energy as thermal radiation (i.e., how long heat is held before being released). Solar reflectance index is a helpful measure that combines both reflectivity and emissivity into one metric.
Finally, realize that there are other ways in which roofing design choices can impact the environment. Urban heat island effects were mentioned above as one larger environmental consideration; another concern in many locales is rainwater management.
As aging sewers are overwhelmed by runoff from non-porous surfaces, especially in urban environments, there’s a need for more control of water flow. Controlling rainwater runoff is not simply a matter of preserving municipal resources; it can also mean keeping pollution out of local bodies of water, decreasing algae blooms related to fertilizer transmission and avoidance of other environmental issues.
Vegetated “green” roofs can help slow this runoff by absorbing water into soil or plant roof systems, as can “blue” roofs designed to store water in sublayers to mitigate the issues caused by rainwater. There are many considerations that go into the proper design of these roofing types, but both can help control runoff if designed well. Whether there are incentives or mandates influencing the decision to build these sorts of rooftops or not, it’s worth considering how your roofing design could diminish the harmful impacts of rainwater runoff while still protecting your building.
It’s Time to Think Bigger
Whether you’re pursuing environmental certifications with your project or not, it’s worth considering how the roofing design choices you’re making are truly impacting the environment and your wallet—whether today or decades in the future. In some cases, the building owner will be seeking an ecofriendly option, in other cases the incentives will come from elsewhere. But regardless, take a long-term view as you consider your options, knowing that there is more than one way to define a sustainable solution.
As an industry, let’s commit to taking a broader view of sustainability. When we look at the big picture of how our roofing construction decisions impact the environment, we can then truly feel confident we’re making responsible choices.