By Tommy Linstroth
The crowning achievement of Leadership in Energy and Environmental Design (LEED) certification can be made a little more reachable by incorporating green roof technology into construction projects. Even more importantly, these types of roofs can cut down on cooling costs during the life of the facilities.
The green roof requirements are part of a LEED credit meant to encourage builders to take steps that “minimize effects [of structures] on microclimates and human and wildlife habitats by reducing heat islands,” according to the U.S. Green Building Council (USGBC).
There are a number of ways that different types of green roofs contribute to LEED certification. The most common is using a light-colored roof membrane to reflect heat away from the building to keep the interior cooler and reduce its heat-island effect.
It’s a matter of basic physics. When exposed to sunlight, dark-colored materials absorb more heat, which increases the amount of cooling needed to keep buildings comfortable. Light-colored roofs, on the other hand, reflect that heat instead of absorbing it, and help keep the interiors buildings cooler.
Although a green roof can directly help check off the heat island credit, it can indirectly contribute to meeting other credits as well. If you’re trying to manage rainwater onsite, you can contribute to meeting overall stormwater management credits by installing a vegetated roof.
A vegetated roof is exactly what it sounds like: a layer of vegetation, planted over waterproofing material, is installed on top of a building with a flat or only slightly-sloped roof. This can be as simple as basic vegetation planted in a shallow growing medium over a roof or an accessible green space that includes a variety of vegetation, including small trees, that building occupants can enjoy.
Finally, many roofing materials have Environmental Product Declarations (EPDs) and Health Product Declarations (HPDs), which contribute towards earning the material credits during the construction process.
In addition to contributing to meeting LEED requirements, green roofs provide tangible benefits to building owners and operators. In additional to reflecting heat, they can be used to help manage and filter rainwater coming off the building. They can provide an additional layer of insulation, which further reduces heat gain.
All of these factors lessen the load on mechanical cooling systems, which lowers energy bills and decreases the wear and tear on HVAC systems. This means less a longer lifespan for what is an expensive capital expenditure.
Finally, green roofs can take a space that is typically ignored and turn it into an amenity for building occupants. Well-designed green roofs provide communal meeting spaces and areas to unwind and catch some fresh air during the work day.
In addition to providing places of respite for building occupants, green roofs can be functional instead of merely ornamental. Some use cases include space for vegetable gardens or beehives that can actually be used to produce honey onsite.
Green roofs aren’t the only way to reduce the heat island effect produced by buildings. LEED includes a variety of other options including:
- Using existing plant material or installing plants that provide shade over paving areas, which can include playgrounds.
- Install shade structures that include energy generation systems like solar cells, thermal collectors, or wind turbines.
- Install shade structures with specific solar reflectance (SR) values
- Building vegetated shade structures.
- Using paving materials with specified SR values.
- Installation of an open-grid pavement system
- Putting at least 75 percent of parking spaces under cover, using a roofing material with specific SR values or that is covered with energy generation systems.
Keeping Up with Changes
Green roofs are a valuable tool for builders seeking LEED certification, but, ultimately, benefit building owners over the long-run in reduced operating expenses and a more comfortable environment. As with any green technology, builders should stay educated on the lasted innovations and material options as well as specification changes in LEED or other green rating systems. For example, the USGBC is expected to ratify LEED v4.1, the newest version of the rating system, at some point during 2020. The changes reduce the difficulty of earning some LEED credits without reducing the value of the certification. So, it definitely pays to stay on top of evolving standards.
Tommy Linstroth is founder and CEO of Green Badger, a cloud-based solution for equipping project teams of all levels of experience with the tools they need to document LEED as efficiently as possible.