CAN/CGSB-51.71-95

1. PURPOSE 1.1 The purpose of this standard is to provide a method for determining whether air moving devices in a dwelling are likely to impair normal venting of fuel-fired, vented appliances through depressurization at the appliance which creates an uncacceptable risk to health, safety or comfort. 1.2 This standard provides a table for determining depressurization limits for particular venting systems. 1.3 This standard defines worst case conditions for a house, and describes how to measure the house depressurization under these conditions by using a pressure measuring apparatus. 2. SCOPe 2.1 This standard applies to detached and semi-detached dwellings. This standard also applies to row houses (Note 1) if they are ground accessible and equipped with self-contained ventilation and venting systems. 2.2 This standard does not apply to dwellings without vented combustion appliances, or to dwellings without air moving devices that could potentially compete with the combustion venting system. 2.3 Dwelling units subjected to renovation, or retrofit in ways that might cause significant changes to the envelope tightness, make-up air supply, or exhaust capacity, may require repeat testing to determine potential for pressure-induced spillage. 2.4 This standard does not remove from the user the responsibility for satisfying other applicable standards, building codes and regulations for the provision of combustion air. 2.5 This standard does not apply to electric heating appliances, or electric water heaters. 2.6 This standard assumes that the installed combustion appliances with their venting systems are not subject to venting problems as may result from design flaws, manufacturing defects, improper installation or inadequate maintenance and repair. For details on how to conduct a comprehensive test of the venting system performance, refer to the "Combustion Venting Student Manual/Reference Text" (par. 11.2.2). 2.7 The depressurization limits presented in this standard are based on the performance of typical vents during the heating season, and are not suitable for predicting summertime performance (Note 2). 2.8 The testing and evaluation of a product against this standard may require the use of materials and/or equipment that could be hazardous. This document does not purport to address all the safety aspects associated with its use. Anyone using this standard has the responsibility to consult the appropriate authorities and to establish appropriate health and safety practices in conjunction with any existing applicable regulatory requirements prior to its use. Note 1: Row houses that are not built to current code can sometimes have problems due to interference from air moving devices in adjoining dwelling. Prior to testing a row house, effort should be made to determine that separating walls are continuous across all heated areas, including any basement or crawl space. Note 2: Fuel-fired hot water heaters connected to vertical chimneys pose a special problem when operated during the summer, in a tight dwelling. Even small amounts of house depressurization may be unacceptable, since flue gas buoyancy is reduced in warmer weather.