Current Approaches for Mechanical Ventilation of Houses

Current Approaches Current approaches to the mechanical ventilation of houses are found in the CSA Standard F326, “Residential Mechanical Ventilation Systems,” and in the National Building Code of Canada 1995. CAN/CSA-F326 The CSA Standard F326 was first published in 1989 and revised in 1991. It is the most comprehensive standard available on this subject, and attempts to address the critical issues in the design and installation of an ideal mechanical ventilation system (see Construction Technology Update No. 14 for a discussion of these issues). The extent to which Standard F326 has been able to do this is limited by available technology. CAN/CSA-F326 is generally written in performance terms (that is, it states what must be accomplished rather than how to accomplish it) and therefore provides a great deal of flexibility with regard to the system configuration needed for compliance. This standard addresses the pertinent issues as follows: Control The greatest shortfall of a system that complies with Standard F326 (hereafter referred to as F326), relative to an ideal system, is in the area of control. Because available technology for demand-controlled ventilation systems does not approximate the ideal very closely, F326 requires only that the system have an on/off switch. Other forms of control, such as dehumidistats, are permitted, but the on/off switch must be able to over-ride them. Capacity F326 requires the ventilation system to have a total capacity equal to the sum of the individual room ventilation requirements shown in Table 1. For most houses, this will add up to about 0.3 air changes Current Approaches for Mechanical Ventilation of Houses