Green roofs are an ideal way for building owners to lower their heating and cooling costs, provide additional insulation, help manage storm water and transform an ordinary roof into a nature retreat for tenants.
And while the demand for green roofs has steadily increased since 2004, particularly in densely populated metropolitan areas, there are several factors building owners should consider before investing in a green roof for their structure.
"Government entities and large corporations are the primary purchasers of green roofing systems, however, there is a growing trend for green roofs within
the condominium, loft and apartment building high-rise market segments," said David Bade, owner of St. Louis-based Bade Roofing Company. "These owners
are looking to convert their less appealing, old roofs and patios into lush living spaces."
A large percentage of the green roofs that Bade has seen in the St. Louis area have been concentrated primarily in metropolitan areas where a green roof is tied to refurbishing an existing structure. Such was the case in 2014 when Bade Roofing was contracted to install a green roofing system on a historic building in Downtown St. Louis that was being redeveloped. Bade crews helped install the rooftop garden courtyard on the building's 5th floor and re-roofed its 6th floor. The green roof boasts views of the Gateway Arch, Busch Stadium and the Old Courthouse and incorporates three-color concrete pavers, various trees and shrubs, a fescue lawn area, lighting, seating areas, watering system and a gas fire pit.
On a green roof retrofit, Bade says it's important to keep in mind that the existing structure was likely not designed with a green roof in mind. The components that make up a green roofing system can be very heavy. Stone ballasts, pavers, trays, trees and soil that become saturated after a rain all contribute to the load that the roof deck and building itself will have to endure. Bade recommends that the building be analyzed by a certified structural engineer during the planning of any green roof project.
Another important factor that building owners should consider is "what happens if there is a leak in my green roof?" Unlike a conventional roofing system where the roof is exposed, the waterproofing components of a green roof are often buried underneath the stone ballast, pavers, growing trays, trees and soil. Bade says an owner and their architect need to be cognizant of repair factors when designing a green build.
"It's best to use light-weight components; ones that don't penetrate the roof system, can be easily moved and don't interfere with roof drainage," said Bade.
When it comes to the roof top vegetation, Bade said building owners need to remember one very important tip, "the taller a plant grows up, the deeper the roots grow down." Bade recommends using growing trays, planter boxes or plants with shallow root systems, as vegetation should not be in direct contact with the roof membrane.
"I have seen plants growing in the dirt and debris that collects on roofs and I have actually seen the roots growing down right through the roofing itself," Bade said.
Finally, Bade recommends that building owners check with their local governments for green building incentives and funding to assist with construction costs.