Ž . Energy and Buildings 29 1999 107–119 Development of an energy rating system for existing houses Radu Zmeureanu a, ) , Paul Fazio a , Sebastiano DePani b , Robert Calla b a School for Building, Concordia UniÕersity, Montreal, PQ, Canada H3G 1M8 b SIRICON, Montreal, PQ, Canada Received 1 December 1997; accepted 3 June 1998 Abstract This paper presents the development of a new energy rating system for existing houses, combining the information from utility bills with on-site measurements and computer simulation. The proposed system was tested on a sample of 45 houses in Montreal, with the Ž. Ž following main objectives: i to evaluate the quality of results given by the system e.g., energy performance of houses, thermal . Ž. Ž resistance of exterior envelope, air infiltration rate , and ii to evaluate the methods of measurement and simulation e.g., time required . on site to collect data, time for computer simulation, accuracy of measurements and simulation . q 1999 Elsevier Science S.A. All rights reserved. Keywords: Residential buildings; Energy; Montreal; Measurement; Simulation 1. Introduction First major step toward the improvement of energy performance of an existing house consists in convincing the owner of potential advantages such as the reduction of utility bills due to energy savings, the increase in thermal comfort or the increase of his property value. There are three main approaches used for this purpose, which can be classified, in terms of the main emphasis, as follows. Ž. a The awareness approach, where the owner is in- formed about the actual performance of his house, com- pared with that of other houses such as an average house, a house built in the same year or a reference energy-efficient house. Sometimes a rating scale is used, similar to that of Ž the quality of services offered by hotels e.g., a five-star . hotel compared with a two-star hotel . In addition to this comparison of energy performance of a house, the poten- tial savings which can be obtained through renovations are sometimes presented to the owner. Ž. b The financing approach, where the owner has access to some advantageous financing schemes for investing in the renovation. Ž. c The quality of work approach, that is, the recogni- tion of professionals and their ability to provide high ) Corresponding author. Tel.: q1-514-8483200; Fax: q1-514-8487965 quality work. The builders associations are usually in- volved in the evaluation of potential savings, and guaran- tee the quality of work, including also the quality of indoor environment or the environmental friendliness. The awareness approach can be very simple or very complex, and its development depends on the expected level of accuracy, the time and cost constraints for per- forming the evaluation, and the final use of the assessed Ž energy performance e.g., for comparison purposes only, for accurate estimates of energy savings, or for convincing the financial institutions to invest in the energy-efficient . renovation . Although this paper concerns only this ap- proach, it is recognized that the use of an optimum combi- nation of all three approaches is the key factor for a successful energy renovation program. A detailed evaluation process is difficult to undertake, since a house is a complex system, where each sub-system Ž . e.g., exterior walls, roof, windows, heating system con- tributes to the overall energy performance, and where the cross effects between sub-systems could play a major role. Different approaches have been developed in the past 10–15 years to evaluate the energy performance of houses, using a simple index, and they are known under the Ž . generic term of Home Energy Rating Systems HERS . These systems can be classified in the following three Ž. main categories: 1 the points system, which evaluates the energy performance of a house by giving points of perfor- mance or scores to each sub-system such as exterior walls, Ž. roof or heating system; 2 the performance system, which 0378-7788r99r$ - see front matter q 1999 Elsevier Science S.A. All rights reserved. Ž . PII: S0378-7788 98 00037-1