Comparative Assessment Of Life Cycle Impacts Of Curtain Wall Mullions

Building and Environment 48 (2012) 135e145

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Building and Environment
journal homepage: www.elsevier.com/locate/buildenv

Comparative assessment of life cycle impacts of curtain wall mullions
Rahman Azari-Na, *, Yong-Woo Kimb
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College of Built Environments, University of Washington, 402 Gould Hall, Box 355720, Seattle, WA 98195,USA College of Built Environments, University of Washington, 120 Architecture Hall, Box 351610, Seattle, WA 98195, USA

a r t i c l e i n f o
Article history: Received 9 June 2011 Received in revised form 4 September 2011 Accepted 7 September 2011 Keywords: Life cycle assessment Inventory analysis Environmental impact Curtain wall Mullion material

a b s t r a c t
Glass curtain wall (CW)systems have been inevitable elements of commercial buildings for over a century. The systems mainly consist of mullion materials and glazing units that are selected and designed to achieve the desired structural, thermal and daylighting performances as well as to meet cost and aesthetic concerns. The health and environmental life cycle impacts of CW systems, however, are not usually considered indesign. The main objective of this paper is to study how change of mullion materials would affect the health and environmental impacts associated with a typical CW system over its life cycle. The mullion materials studied for the purpose of this paper include extruded aluminum, carbon steel and glulam timber. Also, the health and environmental impact categories of interest include global warming,acidification, eutrophication and human toxicity. To achieve the objective, a process-based cradle-to-gate attributional Life Cycle Assessment (LCA) method was applied. Results indicate that CW system with glulam timber mullions causes the least and CW system with extruded aluminum mullions causes the most damage to the environment and human health over their life cycle. A CW system with carbon steelmullions falls inbetween. Ó 2011 Elsevier Ltd. All rights reserved.

1. Introduction The major role of built environment in depletion of natural resources, consumption of non-renewable energy sources and formation of environmental crises that we have been facing over the recent decades has been widely scrutinized by scientists and government agencies. Construction industry is believed to beresponsible for consumption of 40 percent of all extracted materials in the US [1]. Moreover, residential and commercial buildings are estimated to consume about 40 percent of all non-renewable primary energy and about 75 percent of all electricity annually produced in the US and result in about 40 percent of CO2 emissions [2]. As awareness is elevated about the share of built environment in harmingthe environment and jeopardizing the life on earth, the researchers and practitioners in construction industry have started to view the environmental performance of buildings and building products/systems as an important concern to be considered. Glass curtain wall (CW) systems with their usually huge façade areas are inevitable elements of most commercial buildings today. The systems mainly consistof mullions along with glazing units.

* Corresponding author. E-mail address: razari@uw.edu (R. Azari-N). 0360-1323/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.buildenv.2011.09.010

Materials that are usually used as mullions include extruded aluminum, carbon steel and glulam timber [3] which are mostly selected and designed based on required structuralperformance, and cost and aesthetic concerns. Aluminum is the material of choice for most CWs and is used in buildings of various heights [4]. Glulam timber can be used in CWs of low-rise buildings. On the other hand, steel is preferred in high-rise buildings, even though it is applicable in low and middle-rise buildings too. These materials vary in type and quantity of environmental impacts that...