Adding Ventilation to Forced-Air Heat

As energy-conscious builders working in a cold climate, we’ve always provided mechanical ventilation in the houses we build. But our approach to ventilation has changed over the years. At one time, we would put in a 50-cfm (cubic feet per minute) bath fan with some flex vent dropped into the eaves and consider the job done. With today’s emphasis on airtight building envelopes and the associated concern with indoor air quality and moisture problems, however, we’re taking a much closer look at how we ventilate the houses we build. My company mainly builds multifamily housing and a variety of commercial buildings. Because commercial building codes require an automated fresh air supply, we’re quite familiar with mechanical ventilation schemes. Only recently has