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 demonstrate how one might use a life cycle analysis approach to determine optimal insulation levels with a sole focus on environmental impact. The demonstration will include an analysis of commercial roof insulation and residential attic insulation taking into consideration their respective environmental life cycle burdens and operating energy environmental impacts. Embodied environmental material impacts will be estimated using ATHENA's 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. For this paper, two Ottawa buildings will be simulated several times. Each of the simulations will have identical building properties, with the exception of roof or attic insulation, which will vary by amount for each simulation. The analysis will focus on the operational differences between the various roof insulation options, and the development of the operational environmental effects of these different options. For the commercial building, operational energy will be estimated using a DOE 2.2 based whole building operating energy simulator such as EQUEST or EE-4. The building used for the modeling will be an existing two-storey commercial office building. The residential building will be simulated using HOT 2000 software from NRCan. These simulation software systems will allow detailed analysis of building materials and systems including the effects of HVAC systems, envelope systems, geometry, size and location. The paper will present "payback periods" based not on cost, but on environmental effects, for different amounts of insulation. We will demonstrate a method to determine the level of insulation at which the material environmental burden of the insulation exceeds the operational benefits of the insulation. The process used will demonstrate a method to allow building designers the opportunity to base their decision making with respect to roof or attic insulation on environmental effects rather than cost.
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