UPDATED June 27, 2013 with an author’s postscript
Nine years ago, I co-authored a Journal of Light Construction article with David Hansen on HRV installation. The article noted, “Stale air is exhausted from bathrooms, the laundry, and the kitchen. (An HRV is not intended to handle grease or smoke, so a range hood should be separately exhausted to the exterior.) Fresh air is supplied to the bedrooms, living room, and other living areas.” This advice is consistent with the long-standing recommendations of most HRV manufacturers.
The advice is logical: after all, it makes sense to exhaust air from the smelliest rooms in the home and to supply the fresh air to the rooms where people spend most of their indoor hours.
Although this traditional ventilation duct layout works well, I’ve begun to rethink the issue lately. It may be time to experiment with different ducting methods for HRV systems — especially for homes with single-point heating systems.
Ductless minisplits come of age
There is a strong trend among designers of superinsulated houses to use ductless minisplit systems for space heating and cooling. These systems can work well even when outdoor temperatures drop to -17°F or -20°F. Moreover, the systems are inexpensive, easy to install, and very energy efficient.
What type of ventilation system is best in such a home? Since there is no heating or cooling ductwork, a central-fan-integrated supply ventilation system is obviously out. The usual choices: either an exhaust-only system (for example, a bath exhaust fan that runs for much of the day) or a heat-recovery ventilator (HRV) with dedicated ventilation ductwork. (Throughout this article, I’ll use the term “HRV” to include energy-recovery ventilators as well as heat-recovery ventilators.)
Two problems with homes with single-point source heat and HRVs
As more HVAC engineers and builders wrestle…