Research conducted by the British Columbia Institute of Technology shows ICFs can improve energy efficiency and control stormwater on green roofs.
While many research programs focus on concrete's performance in structures and paving projects, one study literally rises above the others. This summer, students at the British Columbia Institute of Technology (BCIT) Centre for Architectural Ecology completed a project that tested insulating concrete forms (ICFs) as a substrate for green roofs.
With its dedicated Green Roof Research Facility, the Centre has become a hub for innovative green roof research and education. Students spent two years tracking the performance of 6x6-foot test structures called Roofing Evaluation Modules, or REMs.
ICF manufacturer Quad-Lock, based in Surrey, British Columbia, supplied materials for the study. The ICF unit (REM-10) consists of an insulated slab foundation rated R10, R-22 walls with 6 inches of concrete, an R-22 roof made of 9-inch Quad-Deck panels with a 3-inch concrete slab, and a green roof layer on top.
The control structure was built with wood-framed walls and roof, and an asphalt roofing layer to simulate a conventional roof without vegetation.
Using the facility's high-tech equipment, students conducted an objective, side-by-side comparison of the roofing materials. A weather station measured rainfall, temperature, relative humidity, wind speed and direction, and solar radiation. Each green roof structure had its own weather pole to track the same variables.
The students embedded equipment into the construction layers of each green roof and collected real-time information with a centralized data acquisition system. Thermocouples provided temperature readings, and heat flux transducers measured the amount and direction of energy flow through the roof for tracking thermal performance and associated energy costs. Runoff drains and buckets measured stormwater runoff rate and quality to gauge its potential for reuse.
Students tested the vegetation on each roof structure, using soil moisture meters to measure water content and studying plant species growth, soil media performances, and maintenance requirements. They also calculated the carbon emissions saved per square meter.
Benefits from above
Under this intense scrutiny, the ICFs performed well. Compared to a typical roof without vegetation, the ICF structure provided several benefits that are increasingly important to owners and designers:
Stormwater Runoff - The ICF green roof retained a yearly average of 69% of the rain that fell on the roof surface, with 31% potentially available for reuse or disposal in a municipal system.
Heat Loss - Depending on the season, the Quad-Lock/Quad-Deck structure reduced heat loss by 50% to 75%.
Heat Gain - Across all seasons, the ICF substrate reduced heat gain by 99%, on average.
“The reduction of heat gain was significant,” says Maureen Connelly, BCIT faculty director. “It can contribute directly to reducing energy costs, specifically in hot climates.”
In terms of heat flow performance, the ICF test structure maintained nearly consistent interior temperatures. “This validates what we hear from ICF building owners,” says Douglas Bennion, Quad-Lock's manager of training and technical services. “They tell us, ‘The temperature just never seems to change in our house.'”
Connelly sees much potential in ICFs for green roof applications, although she stresses the need to evaluate whole building systems. Further research at BCIT, pending funding, will compare different ICF green roof systems, such as planted in situ or pre-cultivated mats, to optimize the performance of ICF structures.
To learn more, visit www.greenroof.bcit.ca or www.quadlock.com.
- Overhead Benefits
This November 2008 article includes project details and a slide show.
- BCIT Roof Study
BCIT data comparing heat flow of the ICF roof compared to a typical roof without vegetation.