Air leaks, overlooking the obvious
Hal Sartelle| Posted inGreen Building Techniqueson
I’m confused why the air lock style entry systems are not incorporated into more homes. An open door leaves a big passageway for the rapid exchange of air. Why don’t prized and awarded homes incorporate this feature more often into the design? A busy house no matter how tight when the door is shut is subject to much cold every time Johnny comes in and out.
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Replies
If the average door is 36" x 80" and it's open for five minutes a day on average, then the door is effectively a 10 sq.in. opening that leaks 24/7. Not so big as you might initially think! Also, in a tight house, where does the big draft of air go? There can't be that big whoosh of air that my grandmother's house had when you open that door. The energy penalty of that air is tiny and the space in the home is dear: who needs an extra room in the house just for going in and out?
Admittedly if you have a 2,400 sq.ft. home and you are aiming at tested air leakage of 0.6 ACH50, then the equivalent hole in you wall for that leakage is on the order of 50 sq.in., so 10 sq.in. added by the door operation might seem like a lot. But also remember, this air enters/leaves by the door, not inside a wall where condensation might occur. Just dial down the HRV a tad and call it part of you ventilation strategy.
In cold climates, a semi-conditioned mud room is a common feature, and I think the fact that it provides the airlock function is a mildly useful side benefit.