A green roof was installed on the Heapy Engineering HQ’s demonstration project by two installers in less than one day.

Heapy Engineering installed a green roof as a “demonstration project” on our LEED-NC Silver headquarters in Ohio in order to show our clients what one looks like, and to know firsthand what it took to design (i.e., structural issues), order, install, insure and maintain one. As design engineers for building mechanical-electrical systems, we especially wanted to verify the potential for energy savings. Thus to accomplish this, we installed temperature sensors in the ceiling plenum under both the green roof and a portion of the original ballasted roof.

Within the LEED-EB: O&M Rating System, a green roof can contribute toward achieving these specific credits: Sustainable Site Credits (SSc): SSc5 Protect or Restore Open Space, SSc6 Stormwater Management, SSc7.2 Heat Island Reduction – Roof, and to a lesser extent, Energy and Atmosphere Credit EAc1 – Optimize Energy Efficiency Performance. Their practicality for your project must be assessed considering a number of good reasons, and good intentions.

Listed (by me), generally in the order of “value” received, a green roof could be installed for any of the following reasons, (including to achieve any of those identified LEED credits):

Stormwater Management — This reason typically produces the most value back to the owner by far. Where local building code requires implementation of stormwater runoff management strategies, a green roof can be a very cost-effective alternative to the traditional solutions of underground or above-ground detention/retention basins, and large storm sewer piping. In zero lot line urban areas, a green roof may be one of your only solutions to stormwater management. Should stormwater runoff be sufficiently reduced, LEED-EB: O&M Credit SSc6 could be achieved.

Reduction in Heat Island Effect — Intense summer sun can create a heat island effect with roof surfaces reaching greater than 150 degrees Fahrenheit. For example, downtown areas are noticeably warmer due to heat island effect driving the local ambient up by as much as 4 to 6 degrees. This creates an unhealthy environment for native animals and plant life. By covering the roof with soil and plants, this heat build-up will not occur due to the transpiration and heat absorption of the plants. Covering at least 50 percent of your building’s roof area with a green roof will achieve LEED-EB: O&M Credit SSc7.2.

Longevity of the Roof — Also by covering up the roof with soil and plants, UV rays and wide temperature swings are mitigated — two of the most damaging factors to roof longevity. Roofs typically provide service life for 15 to 20 years before replacement is necessary. With less thermal and UV stresses to the roof, a green roof can potentially extend the service life of your roof.

Preparation for the Heapy green roof installation project.

Energy Savings — This additional layer of soil and plants provides added (however, sometimes minimal and expensive) insulating value to your roof. Our energy modeling and temperature collection data show that heat gain and loss through the green roof is minimized. The payback on your green roof investment, based on energy savings alone, depends on your building type, use and location.

Saving the Planet/Livability of Space — It is more of a personal call on the first one, but from a “livability” standpoint, having a lush green space to look at certainly refreshes your soul and thus could perhaps contribute to an increase in your productivity. Hospitals use them in their “healing environment” approach to providing healthcare — regardless of the cost — mostly due to the calming (i.e., potential healing) effect that being around live plants has on the human being. Plus plants give off oxygen — the stuff we need to breathe!

Restore Open Space — A green roof can contribute to the restoration of damaged (built upon) sites, especially in urban areas, providing habitat and promoting bio-diversity. Should native or adaptive plant species be used for the green roof, and the green roof covers an area equal to or greater than 5 percent of the total project site area, LEED-EB: O&M Credit SSc5 would be achieved.

Educational / Marketing / Statement — A green roof is certainly a very visible means to display your company’s position on environmental sustainability. We have found the green roof also to be a great educational tool and conversation starter regarding simple and practical approaches to sustainability.

The finished Heapy HQ’s green roof has temperature sensors monitoring heat gain/loss through the green roof as well as an area of ballasted roof to derive the potential energy savings of the green roof.

Additional Considerations

Other factors to consider before you start planting your roof include making an assessment of the roof’s ability to support the weight of a wet green roof and whether its installation will void any existing roofing warranties. Our first step in the process was to contact both our structural design engineer as well as our roof insurer. Our roof structure was designed for 15 pounds of ballast and the green roof was 15 pounds when fully wet. Thus all we had to do is pay someone to remove approximately five tons of rock/ballast to prep for the green roof installation. Once the ballast was removed, we invited our roof insurer to re-inspect the roof and flashings around the entire future green roof area. Finally, we had the insurer provide documentation that our roof will continue to be warranted after the green roof was installed.

Obviously there is much to consider before simply installing a green roof. There may also be much to be gained from doing so (including a few LEED Credit Points). To determine if a green roof is a viable option for your project, it is essential to weigh all factors, including your project’s sustainability goals, budget, building requirements, regional issues and future maintenance concerns. Learn from others that have installed a green roof, and discuss these considerations and others with green roof manufacturers, experts and consultants. Many cities are providing incentives to install green roofs for the reasons described above. Perhaps it will be your project that will enjoy the benefits of the newest rooftop park!

If you have installed a green roof, share your experiences and results with Sustainable Facility readers at maytonj@bnpmedia.