When I woke up Saturday morning, the temperature outdoors was -40 degreesâ€ . The wind chill was -100 degrees! It was just unbelievably, impossibly, inhumanly cold outside. Fortunately, that was on a mountaintop in New Hampshire and not where I was. I happened to have woken up on a mountaintop in North Carolina, where the temperature was a much warmer -3°F.
And when it’s cold outside, most people prefer to be in warm, cozy home with no drafts. Of course, we all know that no drafts means we have good airtightness, and good airtightness means we need mechanical ventilation. But how do you ventilate a home when it’s really, really cold outdoors without causing problems? And what are those problems with cold weather ventilation?
Three whole-house ventilation strategies
Exhaust-only ventilation. This one’s the cheapest to install and the most common. It relies on fans that are already in the home: bathroom exhaust fans and kitchen range hood. These fans are set to run continuously or intermittently with a controller. As they exhaust air from the home, the resulting negative pressure inside causes air from outside to come in through leakage sites in the building enclosure.
Supply-only ventilation. Like exhaust-only but the fans blow outdoor air into the house, creating a positive pressure. It can be done with regular bath fans or specially designed fans or by hooking up a controller to the central air handler.
Balanced ventilation. Most people automatically think of the energy recovery ventilator (ERV) and heat recovery ventilator (HRV) here, but balanced ventilation simply means supplying and exhausting equal quantities of air. I’ve written previously about different ways to do balanced ventilation.
When it’s really cold, bringing in outdoor air needs to be done with some forethought. There’s a…