It's something else again to crack all the windows open in your home when you have the air conditioning running. After all, there's something more to be said for wasting energy – and a lot of it. But will closing vents in unused rooms help cool your house better?
On balance, this idea sounds like it has some merit – if, that is, the air that is blocked from one room or rooms because of closed vents simply skips over to a room or rooms with open vents.
And therein lies the problem: This is not the way your duct system works. In a nutshell, when cool air comes rushing through a duct, only to be met by a blocked vent or register, much of the cool air stays right where it is. And it definitely doesn't travel to another room or rooms.
So in the end, this perfectly logical scenario fails to achieve two objectives: it will not cool a home any better and – if you had hoped to reduce your electric bill – it will not save you a penny.
A comprehensive study on the issue conducted by no less an authority than California's own Ernest Orlando Lawrence Berkeley National Laboratory actually concluded that “register closing led to increased energy use."
How's that? Air pressure builds up in your ducts as cool air tries to travel through a register but is blocked from doing so. The air wants to go somewhere, and some of it does: through cracks and gaps in ducts that aren't sealed or connected properly – and most homes have them somewhere. Some pent-up air also escapes through floor activities. Combined, the laboratory considered these energy losses to be “significant.”
The consequences can become worse as more registers are closed, the laboratory said. Researchers found that closing “too many registers” – or more than 60 percent of those in a home – resulted in air flow resistance problems that could damage an air conditioning system and potentially lead to costly repairs, especially if the system's coils freeze.
The laboratory included one interesting proviso: “Closing registers farthest from the air handlers caused fewer leaks and tended to affect only the closed off branches, but closing registers nearer the air handler tended to increase duct pressures the most and cause air leaks throughout the whole system.”
Still, this finding wasn't compelling enough to change the laboratory's bottom-line conclusion: “The register closing technique is not recommended as a viable energy saving strategy for California houses.”
So what can you do to keep your home as cool as possible and save money on your summer energy bill? For starters, consult these blog articles for many informative air conditioning articles and easy-to-implement ideas.
Before closing any vents in your home: