Ask Adam: Does Closing Room Vent Save Dollars?

By: Adam's Air Conditioning Date: 2016-07-11
Dear Adam,
Our only daughter is leaving for college in the fall. I'm wondering if there's a possible tiny bright side to this empty nest that my wife and I are facing. Her bedroom will still be hers until she graduates and fully moves out, but until then, I thought I'd close the air conditioning register in her room and shut the door while she's away in an effort to save a few dollars on our electric bill. But my wife says no, that she read that it's not the thing to do, contrary to popular belief.
Stephen Howell
Port Saint Lucie

Mr. Howell, Mrs. Howell is one smart lady. Although your concept does seem logical and I've heard lots of similar mentions over the years, it's not a good idea. Not only will shutting the vent into your daughter's bedroom for semester-long periods invite mold and mildew growth, but it will throw off the air balance of air circulation in the rest of your house.
Typically, duct work is designed to work all together, and vents are calibrated to sustain certain air flow rates to maintain equal temperature throughout a home. If you close off one room, it throws everything out of balance. At the least, you could find one room frigid while another too warm. At the worst, you could create a mold infestation and cause damage to system components from the pressure imbalance.