This article will explore the ability of each of the following exterior building envelope systems to help reduce the carbon footprint of your facilities:
We will look at the contributing benefits of these components in relation to ten critical categories of sustainable design:
As a cautionary note, manufacturer hyperbole about the “greenness” of various products has resulted in the coinage of a new term: greenwashing. To avoid becoming the victim of exaggerated claims when searching for alternative sustainable solutions, be sure to assess:
When assessing the LEED point potential for various building exterior components for the purposes of this article, we will be evaluating those aspects of performance fostered by LEED, namely:
The use of reflective coatings on roofs to reduce the energy required to keep building interiors cool has become an increasingly controversial topic in recent years. Many building owners, particularly in the public sector, have become wary of the one-regulation-fits-all approach being taken by some states and municipalities. The building industry, from architects and designers to manufacturers and consultants, have also expressed concerns that reflective coatings, when used in northern regions of the country, may inflate construction costs with no appreciable effect on energy cost reduction.
Nevertheless, when appropriately specified, reflective roof coatings provide the quickest return on your sustainability investment by realizing energy savings worth as much as twenty cents per square foot for commercial buildings6. This benefit is particularly apparent for buildings that draw rooftop air into their HVAC units, since it takes far more energy to reduce hot 185°F (85°C) air down to a comfortable 70°F (21.1°C), than it does to cool air that enters the HVAC at a cooler 110°F (43.3°C) temperature. Since the reducing the use of fossil fuels is a primary driver behind LEED certification, reflective roofing typically rates high for LEED point contribution as well.
Reflective coatings offer the additional benefit of extending a roof’s service life by increasing UV resistance and reducing the thermal shock associated with extreme fluctuations in rooftop temperatures.
The final area in which reflective coatings are currently providing a real competitive advantage is in eco-related governmental approvals, tax credits, etc. Since the reduction of fossil fuels remains a primary governmental concern and reflectivity is the exterior design solution most frequently associated with energy savings, there may be powerful local incentives for choosing this sustainable design option.
Your roofing material manufacturer or design professional can help you determine the probable financial impact of a cool reflective coating, based on your regional climate and other factors such as shade-creating surroundings.
From an aesthetic perspective, white reflective coatings remain popular with the design community. Where aesthetics are not a driving concern, aluminized reflective coatings may provide a cost-effective sustainable alternative; there is also evidence that aluminized coatings offer better energy savings than white coatings when used in northern climates.
Some reflective coatings incorporate biobased and/or recycled content, for example, soy oils. Always check with your roofing manufacturer to determine whether such options are available. From a service life perspective, reflective coatings offer the advantage of extending the time between cradle and grave.
Although undoubtedly the least sexy of the many sustainable solutions on the market today, there have been great advances in the design of restoration and maintenance materials for both roofs and walls. This makes the restoration/maintenance category an ideal starting point for school districts and other capital-stressed organizations committed to reducing their carbon footprint.
For roofs beginning to show their age, restoration can extend service life by ten years or more. Restoring an aging roof has the immediate tax benefit of a maintenance, rather than capital expense, for private sector building owners. In addition, all facility owners will benefit from the postponement of reroofing and the landfill-destined waste associated with tear-off. If the restoration coating is reflective, additional benefits by way of energy cost reductions may be gained, depending on geography and other factors, as previously described.
Beyond these obvious benefits, the formulation of today’s restoration coatings, as with the formulations of many next-generation maintenance materials, have changed radically over the last 20 years. There are green (or at least “greener”) alternatives in almost every category of building exterior maintenance.
The longevity of a properly installed modified bitumen roof can rival the service life of metal roofing. Although modified bitumen roofs may not provide the design flexibility of metals, they do offer strong aesthetic appeal when combined with a highly reflective coating or bright white mineral surfacing.
Historically, the quality of modified membranes has varied greatly, based upon factors such as the tensile strength of their reinforcing materials, the amount and quality of rubber modifiers used, and the method used to mix the polymer into the asphalt. Today’s membranes also vary in regards to their level of “green” fabrication. Specifically, depending on manufacturer and style, a modified roof may provide:
The addition of vapor barriers to an exterior renovation or new construction can contribute to energy cost reductions by optimizing air flow and eliminating unwanted moisture. Although vapor barriers do not have the cachet of more obviously “green” building solutions, they are an excellent example of an engineered component that can allow a building owner or facility manager to modestly impact a building’s carbon footprint while ensuring watertight performance.
A roof system capable of sustaining the foot traffic associated with installing and maintaining a rooftop solar array should be a high-performance roof system that is built to last. Providing protection that is both watertight and ecologically responsible is the goal of every rooftop solar solution.
Since solar systems are essentially capturing and repurposing existing solar energy, they are in a category unto themselves. Although their return on investment may be proportional to a system’s average exposure to sunlight over an extended period of time, given their current costs, a more rapid return on investment can only be achieved through government and/or utility incentives, regardless of climate.
Rooftop solar also scores well in LEED point contribution and eco-related approvals, with their associated rebates and tax credits. However, they do have some drawbacks, including a relatively high carbon footprint during their manufacturing phase; little to no recycling potential; an aesthetic that can be disruptive to a building’s overall design; and the fact that most of today’s solar solutions are manufactured overseas.
Taking that first step towards a sustainable future is the responsibility of each of us, whether we are actively engaged in the building trades or the stewards of public or commercial properties. Whether you are planning an ambitious new construction project or struggling to get the best possible return out of your aging properties, affordable green alternatives are available in many critical areas of exterior construction, renovation, and maintenance. Work with your architect, engineering professional, or building material supplier to determine a first step that’s right for you.
