The idea of closing register vents isn’t new. The premise is simple: some rooms are overheated in the winter while others are overcooled during the summer. By directing the conditioned air into rooms that are heavily used and closing the vents in rooms that are underused, by theory, you should be saving energy. But does it hold true?
The answer is probably not. While very few studies have been done on this matter, one was conducted by the Lawrence Berkeley National Labs a few years back. In it, they found that closing registers actually increased energy consumption. But why?
When air is forced through a venting register, it increases in pressure as the register vents are closed. This forces the air through leaks and gaps in the ventilation system. When the air leaks from the ducts, it creates a strain on the heating/cooling system by forcing the system to work harder. So whatever savings in energy consumption that goes with closing vents is canceled out by the effects of air leakage through the vents.
While not everyone has leaking air ducts, it is a common occurrence in many homes, especially older ones. According to some studies by the U.S. Department of Energy, air leakage in ducts can account for a 20 percent loss on every dollar. That translates to one dollar out of every five lost in the attic, basement and crawlspaces in your home through leaking ducts.
Even if your air ducts are well sealed or don’t leak much, closing the registers still might not be a good idea. Closing registers can increase air pressure, reducing the air flow across the heat exchange coil, leading to damages and disrepair. Increased air pressure in the system can also lead to compressor problems, potentially ruining your air handler permanently.
Closing your air vents in the summer can lead to even more damages. When cold air is pressurized and hot air is introduced to the system, it creates humidity in the vents. And when registers are closed, that humidity is allowed to collect onto the registers inner surface. This can lead to mold, mildew and a host of other pathogens that are dangerous if left to harbor inside of the system.
Some companies offer remote controlled vent closing systems that close the registers automatically. These and other products that are similar in design often claim that their systems reduce energy costs. But the bottom line is more often than not filled with pitfalls and troubles, making closing your register vents more of a problem than what it’s worth.