Does Closing AC vents in Unused Rooms Save Energy?

closing-ac-ventsBalance is a tricky thing to achieve in any facet of life, but it’s much harder when you don’t fully realize what you’re dealing with.

For example, in the summer it can be incredibly tempting to forgo cooling unused rooms in order to strike a balance between your cooling costs and your comfort, but as it turns out, this is one of the worst things you can do for your pocketbook.

 A Central Air Conditioner’s Balance

Your central air conditioner is a pressurized whole-house system, designed to distribute cool air evenly and efficiently to each vent attached to the ductwork. Your air conditioner’s air handler was selected by your air conditioning expert for its ability to cool your entire home at one go, but when you shut the system down in part of your home, the square footage that unit has to cool is reduced dramatically — which sounds like a good thing. After all, your goal is to concentrate the air conditioning only in the rooms where you really need it, right?

In truth, when you close down rooms, you increase pressure in the system and create even bigger problems. All that pressure eventually gets relieved, and depending on the cause, it can be bad for both you and your system. A closed off vent causes pressure to build inside the ductwork, which eventually results in leaks and the failure of duct seams.

A closed-off room with an open vent, on the other hand, blows off its excess pressure through cracks, windows and any other openings available. That might not sound like a problem, but a home is a fairly closed system, and when the pressure drops dramatically in the bedroom, outside air from those (now-widening) cracks is drawn inside, unfiltered, and is full of all sorts of pollutants that can build up inside your home. Cooler areas tend to attract heat, so eventually that warm air in your closed rooms finds its way into the main part of the house, forcing your air conditioner to kick on more frequently to overcome seeping outdoor air. Eventually all those extra cycles will burn out the compressor — or the high pressure will destroy your air handler.

Tricks for Saving Cooling Dollars

Cooling your home on a budget is a complicated dance, to be sure, but it’s important to understand that modern air conditioning considers the whole house as a unit. You can’t force your system to be more efficient. There are, however, things you can do to increase efficiency, such as:

Install Light-Blocking Shades.  The more of the sun’s rays you choose to block, the cooler your house. Windows are among your biggest efficiency losers. Even a high-efficiency window is no match for a wall or door when it comes to preventing heat transfer from outside.

Seal Your Home Tightly.  Caulk around windows, doors and trim to prevent air seepage from outside. Take a look at door sweeps and other potential sources of outside air, like fireplaces, to ensure that all seals are in excellent shape.

Maintain Your Air Conditioner.  A well-maintained air conditioner is an efficient air conditioner. Before the summer heats up, clean your outside unit thoroughly with a garden hose to dislodge any dirt or dust, straighten bent fins with a fin comb and destroy any vegetation trying to grow through the unit. If your unit sits out in full sun, protecting it with a shade can help it perform better.

Check Your Filters.  Dust-impregnated filters block airflow to your air handler, giving it less air to cool and send back into your home. Keep those filters checked and changed, and you may discover that the only thing you need to do to increase efficiency is to move more air into the system.

Turn on Indoor Fans.  There’s something magic that happens when you start pushing air-conditioned air around a home — most people find that it feels much cooler even when the thermostat is set higher. Give it a try: leave ceiling fans running, place fans in dead corners and encourage as much air movement as is reasonable in your home, then turn up the thermostat at least two degrees.

Precision Air & Plumbing August 21, 2017


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