In the 20 years that I've been building homes, I've seen a dramatic rise in the demand for mechanical ventilation in general and for heat-recovery ventilators (HRVs) in particular. Much of this demand is thanks to the growth of utility-sponsored newconstruction programs. These programs recognize that natural ventilation is not a reliable way to provide fresh air for the people in a modern home. Mechanical ventilation is the only reliable way to do the job. Despite the new awareness, many builders still think that ventilating a home means putting in a range hood and a bath fan. Unfortunately, that's not enough. A good ventilation system not only removes stale air from kitchens and baths, but it also supplies an