Carleton’s Green Roof – Monitoring its Performance

Carleton broke ground in June 2009 for a new building to house the expanding engineering programs of biomedical, sustainable energy, environmental and aerospace engineering. The brand new seven-storey Canal Building, which opened in February 2011, includes many sustainable design features including five out of five Green Globes through the Green Globe rating system (see more in the Carleton Now article A key sustainable design feature is the inclusion of a green roof, a “living” roof of plants on a smaller section of roof covering part of the sixth floor. This green roof is similar in size and location to a conventional roof located on a section of roof covering part of the fifth floor.

The green roof will be used as a teaching tool and learning centre for students studying at Carleton University. Both green and conventional roofs are instrumented to measure thermal gradients, storm water storage and run-off, weather conditions, and solar radiation. This instrumentation enables the comparison of performance from both roof types.

Unlike the conventional roof, the green roof has 12 different varieties of plants. The Canal Building green roof is an “extensive roof”, designed to handle low profile plants with only a shallow soil depth. The roof design also has small growth trays instead of being entirely covered in soil for ease of maintenance.

The outcomes of the ongoing monitoring demonstrate the potential benefits of green roof research. These include energy savings and increased roof life-span. Green roofs can also clean the air, reduce stormwater runoff, and reduce the “heat island effect” – increased temperatures in urban areas. The conventional and green roof can be compared by looking at each “water budget”- a method to track how much water enters, leaves and is stored in the system. Similarly, the roof’s “energy budget” measures the reduction in energy requirements in the building. 1

The data acquired from both the green and conventional roofs will eventually be displayed in the foyer of the Canal Building as well as online. Easy access to data acquired from both roofs will not only educate current Carleton students, but will allow for outside parties to benefit from the green roof research.

This green roof research is innovative and essential to continued research in sustainable building design. This research goes hand-in-hand with Toronto’s implementation of their Green Roof Bylaw, which requires large commercial, industrial and residential buildings to include a green roof on part of their roof depending on the size of the building (see more at ). The Carleton Green Roof is just another way Carleton is contributing to sustainable energy research.

1 Statistics based on the report Instrumentation and Preliminary Research for Carleton Green Roof by Robyn Chatwin-Davies

Article by Andrea Pietila, M. A. Sc., Carleton University
With support from Robyn Chatwin-Davis, Environmental Engineering student, Carleton University, and Dr. Liam O’Brien, Department of Civil and Environmental Engineering