Energy efficient window retrofits in historic facilities

Abstract

Owing to an ever increasing emphasis on reducing energy usage in buildings, the older windows found in historic buildings are often in danger of being replaced during rehabilitation projects. These older windows are replaced with more energy efficient models that often do not match the existing historic appearance. It is well documented that windows are poor insulators causing increased heating or cooling load, depending on the weather conditions, and thus are the usual targets when trying to improve a building's thermal performance. This paper discusses the somewhat dissimilar goals of the federal government's energy management program and its historic preservation policies. The main purpose of the paper is to suggest and recommend alternative methods of improving the energy efficiency of existing historic windows while at the same time maintaining the significance and character of the window units. Several case studies are examined that support the repair and rehabilitation of windows to both retain historic materials and to also reduce energy consumption. Many owners and architects, impatient with the time consuming demands of preservation, forfeit valuable historic resources in favor of the expediency of window replacement. In most cases the alternative methods produce energy savings equal to or greater than the savings gained by replacing windows with newer models, at a lower cost.