The Impacts of Green Building Strategies on the Durability and Performance of Building Enclosures

Over the last 10 years the concept of green buildings has become an important, and an increasingly large part of building design and construction. The success of LEED, and similar rating system, (both in terms of environmental performance, and more conventional evaluation criteria) have demonstrated the benefits of green design. The well-publicized success of green buildings reinforces demand for more green buildings and requires that all design professionals have, or purport to have expertise in this area. While the impact of sustainable design and of green building rating systems will no doubt be positive over the long term, there may be dangers associated with the rapid application of these systems and associated green design strategies involving the use of innovative materials and technologies. Specifically, the question of whether the application of specific green design strategies may result in problems of building durability and performance has been raised. Of particular concern is the potential for inadequate building enclosure performance. A recently published paper on the subject of building enclosure commissioning focuses on a LEED Platinum building in the US and makes a direct connection between building green and a range of identified building enclosure problems. The history of earlier attempts to improve energy performance in buildings can provide useful lessons for green design. The implications of increases in insulation levels and increases in air tightness for building performance, and in particular on enclosure performance were often not fully understood, resulting in a range of problems. This paper will present the results of an investigation into the implementation of green building strategies and their effects on building enclosure durability and performance. Various green building rating systems will be reviewed and the strategies typically applied to achieve specific ratings will be analyzed. Based on surveys of practitioners, case studies of completed green buildings, and practical experience of building enclosure design and construction the positive and negative impacts of these practices, potential or actual, will be documented. The conclusions of the study and recommendations for improving green building strategies and communication between building enclosure practitioners and green building designers will be presented. This paper is based in part on research carried out for a study commissioned by CMHC on the subject of green buildings and durability. Limitations on the length of this paper have required that detailed discussion that forms part of the larger study be curtailed and that background information and analysis be summarized. The CMHC study addressed the performance and durability of both the building enclosure and of HVAC systems with an emphasis on residential buildings. The primary focus of the paper is on issues relating to durability and performance of the building enclosure. However, the survey of practitioners provides a wider context for these issues by also identifying a range of other potential impacts of green design. It is assumed the reader will have a basic understanding of the LEED (Leadership in Energy and Environmental Design) rating system and of the integrated design process (IDP).