Historically, cost has been the primary factor driving the specification of building envelope components and systems. Recent trends towards environmentally conscious design and construction have resulted in a focus on the environmental impacts of material selection, with emphasis on a life cycle approach.

This paper will compare and contrast several different types and amounts of insulation within commercial roofing systems taking into consideration their respective environmental life cycle burdens and operating energy environmental impacts.

Embodied environmental material impacts will be estimated using thte ATHENA^® Environmental Impact Estimator software. The ATHENA^® software is a Canadian developed and internationally recognized means of obtaining comprehensive and reliable environmental life cycle burdens of building assemblies. It covers building material and system life cycle stages from the "cradle" (natural resource extraction or recycling facility) through to its "end-of-life" (grave). For this paper, results reporting of material effects will include embodied energy and global warming potential as indicators of environmental burden.

Operational energy will be estimated using the EQUEST operating energy simulator. EQUEST is a DOE-2.2 simulation software that allows detailed analysis of building materials and systems and includes effects of HVAC systems, envelope systems, geometry, size and location.

For this paper, a fictional two-storey office building will be simulated several times. Each of the simulations will have identical building properties, with the exception of roof insulation, which will vary by amount and type for each simulation. A simulation for each building (insulation) option will also be run for both Ottawa and Vancouver climates. The analysis will focus on the operational differences between the various roof insulation options for both a cold and moderate Canadian climate, and the development of the operational effects of these different options.

Ultimately, this paper will present "payback periods" based not on cost, but on environmental effects, for the different types and amounts of roof insulation. The process used will allow those involved in the building industry the opportunity to base their decision-making with respect to roof insulation on environmental effects, as well as cost.