The Feasibility of Green Roofs at Calvin College

Research into the feasibility of adding green roofs to Calvin College buildings.

Professor J. Aubrey Sykes and Ha Ram (David) Kang

Green roofs consist of soil and plant layers placed over the roofing, usually a mastic or rubber layer, of a –generally—flat roof. Calvin College is one of the few academic institutions without some application of green roofs, and—evidently—the only college in the Grand Rapids area without at least one green roof; some local colleges have several.

The principal advantages of a green roof are management of water runoff (converting most of the precipitation to water transpired to the atmosphere), insulation effect (reducing energy losses or gains through roofs), and substantially extended life (indications are to 30 years vs. 7 years) for the roof ‘s mastic or rubber seal. Maintenance is low consisting of minimal (e.g., annual) debris removal and occasional watering in the event of droughts.

Our examination of the feasibility of applying green roofs at Calvin College resulted in these recommendations:

1. Further examination of what would have to be done to apply green roofs to Calvin College’s existing buildings. All of Calvin’s existing buildings were surveyed for green roof suitability and three were identified for potential. However, a green roof adds a roof load of 25 to 400 lb force, depending on the complexity of the roof (we were principally considering the lower load). Discussions are continuing with civil-structural engineers and architects to determine what would have to be done to allow green roofs on to the selected buildings.
2. Establish a campus policy that all future construction or modifications of campus buildings would be required to justify not applying a green roof.
3. Establish a student project to build and monitor a demonstration project. The demonstration facility would most likely be located on an open area on DeVries Hall. Here two large panels would be built in similar layouts; one would contain a green roof panel and one would be a typical current green roof panel. Each would be instrumented equivalently to assess the mangement of precipitation, transfer of heat and incidence of destrutive solar radiation. The students for this project would come from Engineering, Biology and Business or Economics. The facility would help all to become acquainted with green roofs and their benefits.
4. Increase students’ awareness of green roofs and their auxiliary facilities througn seminars, site visits, and in-class discussion and problems. Auxiliary facilities include rain gardens for collecting excess runoff, and vertical green roofs applied like exterior Trombe walls.

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