Comparative assessment of life cycle impacts of curtain wall mullions

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 in design.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 steel mullions falls in-between.