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ABSTRACT
Energy ratings are currently being used in a number of countries to assist in the selection of windows and doors based on energy performance. Developed for simple comparison purposes, these rating numbers do not take into account window removable attachments such as insect screens that are, nevertheless, widely used. Research was carried out to assess the effect of insect screens on the heat gains and losses of windows. The work reported in this paper deals with the effect of one screen type on the performance of a base-case, double-glazed window. Using an indoor solar simulator facility, measurements of the window solar heat gain coefficient (SHGC) and U value were made for different screen attachment configurations and climatic conditions. Results with the sample window tested indicate that insect screens placed on the outdoor side can reduce its SHGC by 46% with only a 7% reduction in its U value (0. 19 W/m^sup 2^ degC), and that insect screens placed on the indoor side can reduce its SHGC by 15% while reducing its U value by 14% (0.38W/m^sup 2^ degC).
INTRODUCTION
House envelopes, including windows and doors, are becoming more energy efficient, so rating systems have been developed to allow for fair and simple comparison between window options based on their energy performance. These rating system do not take into account the impact of removable attachments, in particular insect screens that are widely used in North America and other countries. The reasons are that such attachments are optional, are typically used on a seasonal basis to varying degrees depending on the location, and therefore are not consistent with a rating system that is meant to be as uniform as possible.
Modeling tools for assessing window or whole-house energy performance are increasingly being used for design purposes and product selection, not just for comparison of product energy performance. As it was suspected that insect screens had a significant impact on window energy performance, in particular for the high-performance windows, there was clearly a need for evaluating this impact It was decided that experimental assessment would first be conducted for common configurations, followed by modeling of the impact of attachments for incorporation into existing energy performance simulation tools. For illustration purposes, the impact of adding an insect...