How to Beat the Heat When Your Central Air Doesn’t Reach Upstairs

Getting the air conditioning upstairs in an older home can be a tall order. Here are some big and small fixes to cool off hot spots upstairs.

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We all know that heat rises and cool air sinks, but physics may not be the only reason your central air isn’t reaching upstairs. Many older homes have aging and inefficient HVAC systems and ductwork. And while many modern homes have separate HVAC systems for upstairs and downstairs, many older homes do not. All this can make cooling down warmer areas of the home a challenge. From quick DIY fixes to HVAC system upgrades, discover ways to beat the heat and coax air conditioning upstairs.

1. Redistribute air with vent seals and directional covers.

Woman putting vent cover over floor HVAC Vent

One of the quickest ways to force cool air upstairs is to close a few vent registers in the basement and lower level of the home. Metal registers usually have a small lever that toggles the louvers open or shut. If closing the louvers is not enough to redirect airflow, you can use magnetic covers to seal the vent.

If your vents are in inconvenient places like behind or beneath furniture, a directional cover may be the solution. For a vent located under a couch, an air vent extender can direct the flow out from under the couch so that cool air is not trapped underneath.

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2. Change air filters regularly.

Man replacing dirty furnace filter in home

Air filters help keep indoor air clean by capturing and filtering out particles such as dust, pet dander, smoke, and mold spores. But they need changing regularly to remain effective. Dirty or clogged air filters can block airflow and increase stress on an HVAC system, so be sure to change filters regularly. Most disposable air filters should be replaced every 90 days.

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3. Get air boosters for your registers.

Air booster fitted onto floor vent

A register booster is a fan that fits flush into your vent register and plugs into a nearby outlet. The fan increases air circulation by drawing cool air from the duct system into the room. Most register boosters have various fan speed settings, and some have programmable modes and smart sensors to detect temperature changes.

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4. Keep the thermostat fan on.

Woman's hand changing fan setting from auto to on

The default setting on central air thermostats is usually “Auto,” which sets the central air system’s fan to engage whenever the AC starts. Once the thermostat reaches the desired temperature, the fan shuts off along with the unit. Keeping the blower set to “On” will keep the fan running independently, whether the AC is on or not. Keeping the fan on will keep air moving throughout the house and help to balance temperatures in hot zones.

RELATED: The Best Programmable Thermostats for the Home

5. Use fans strategically.

Attic Bedroom with ceiling fan

Ceiling fans can be valuable complements to central air systems in areas like upstairs bedrooms and home offices, where staying cool is especially important. In warm months, the fan should be set to rotate counterclockwise, which will push air down and create a breeze with a cooling “wind chill” effect. If the outside temperature dips during the night, you may want to use a window fan to draw the cool air inside.

RELATED: The Do’s and Don’ts of Window Fans

6. Keep the heat out.

Man hanging grey curtains on window

Finding a way to increase the flow of cool air into warm upstairs rooms will be no use if hot air keeps getting in. Find ways to eliminate sources of heat in hot rooms. Sunny windows may be bright and cheerful, but they can quickly heat up a room by several degrees. Keep windows closed during the day, and cover sunny windows with thermal light-blocking drapes to keep scorching air outside.

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7. Check ductwork for leaks.

Worker Insulating an Attic Vent Duct with Aluminum Foil Tape

Old homes usually have old ductwork. Over time, ductwork can deteriorate from age, thermal stress, and vibration. This movement can cause cracks in seams that cause inefficiencies in airflow, excess moisture, and energy loss. Check your ductwork for loose connections and visible holes and seal them with HVAC aluminum foil tape and duct sealant. If your ductwork is difficult to access, get a professional to perform a thorough system analysis to locate leaks and repair them.

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8. Rebalance your HVAC system.

Air conditioner check service, leak detection, fill refrigerant, device meter liquid cooling

While closing registers is a quick DIY way to help balance the airflow in a home, an HVAC technician can perform a professional balance of your HVAC system. A technician will take air flow and temperature measurements throughout the home to identify problems and adjust the duct and AC dampers to help redirect air conditioning upstairs.

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9. Insulate your attic.

Back view of two professional worker in overalls working together with rockwool insulation, standing inside new house under construction, fasten warmth material on ceiling and wall with copy space

Many older homes have uninsulated attics with poor ventilation. In warmer months, attics without insulation can reach extreme temperatures as they absorb the sun’s heat. This heat, in turn, radiates down into the rest of the home. Getting your attic insulated is an investment, but in the long run it will reduce your energy bills and reduce strain on your HVAC system.

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10. Install a zoned system.

HVAC Technician Checking Units Outside House

Older homes often have one thermostat that controls the entire home’s internal temperature. A digital zoning system is an HVAC system upgrade that divides the home into multiple areas, or zones, with customized environmental controls for each area. This way, cooler areas like the basement can stay comfortable (without getting too cold) while the HVAC system directs cool airflow to upstairs hotspots.

11. Replace central air with ductless mini-splits.

Mini-split ductless air conditioning unit installed in unfinished room with painter's tape around it

Poorly designed or retrofitted ductwork can make central air ineffective and result in inflated energy bills. If your home has old and inefficient ductwork, you may consider replacing your central air conditioning with ductless mini-splits. Mini-split systems have many advantages, including customized temperature control in each room or zone, low operating costs, and energy efficiency.

12. Get an AC tune-up.

HVAC Technician Checking HVAC Unit

The age and health of your air conditioning unit can greatly affect its efficiency. If airflow imbalance and hot and cool spots in your home are becoming a problem, get a professional to assess the health of your AC unit. An AC technician will check for refrigerant levels, cracks and dirt in the coils, and any debris that may be stuck in the outdoor unit. Scheduling regular maintenance checks on your AC unit can help extend its life by catching problems before they turn into major issues.

13. Install a window AC unit.

Woman turning on window unit AC with remote control

Although there are several ways to help usher air conditioning upstairs, there’s no fighting the law of thermodynamics. When all else fails and your upstairs bedroom or office stays uncomfortably hot and starved for AC, you may choose to install a window unit, like the GE Electric Window Air Conditioner at Amazon. Window air conditioners are reasonably simple to install and can provide sweet relief to a sweltering space.

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