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Reasons the AC Cools Unevenly | Diagnosing Uneven Home Temperatures

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Dealing with a house that’s either too hot or too cold during the long Austin summer is inconvenient at best. If you’re noticing that one room in the house is always cold while the other end of your home feels dissimilarly hot, here are some common reasons:


An incorrectly-sized AC unit can create a range of issues, the most costly of these being accelerated wear and tear. But even while still in its prime, a unit that’s too big or too small simply won’t function optimally and can be why the temperature across your home isn’t consistent. Schedule an appointment to have a professional assess your current AC unit to determine if size is contributing to your problem.

Signs Your AC Is Too Small
An AC unit that’s too small for the house is an obvious problem: it won’t have the capacity to handle your home’s cooling demands. As a result, your home experiences hot spots, and your unit is taxed beyond its abilities.
Signs Your AC Unit Is Too Big
Believe it or not, a large unit won’t cool a small space more efficiently. When your air conditioner is too big, it will put out cold air very quickly – too quickly for the unit to complete its intended cycle. This resulting “short-cycling” causes uneven temperatures across your house, and ironically places additional stress on your system.


If your air conditioner is consistently not keeping up to cool your home or parts of it, consider its age. Struggling to cool or providing uneven cooling is a major sign of an air conditioner that’s reaching the end of its lifespan. If your unit is older than 15 years, chances are it’s time for a replacement.
Learn more about air conditioner replacement now.


Your AC vents allow cold air to move from your ducts into the various parts of your home. If the vents are blocked, air can’t move freely, resulting in warm and stuffy areas throughout the home.

Blocked Supply Vents
Your home’s air supply vents are usually located high up on the wall or in the ceiling, although some homes have supply vents installed in the floor as well. Either way, you’ll be able to identify your supply vents because they’re the ones blowing air into your home.
If you have a room that’s not getting enough cool air, it may be as easy as opening the louvers on the vent. If the vent is already open and blowing plenty of air, ensure you haven’t impeded airflow with tall furniture such as bookshelves etc.

Blocked Return Vents
The return vent takes your home’s air back to the HVAC system. Return vents are usually larger than supply vents and they don’t have louvers. However, they can still become inadvertently blocked by furniture or other items. When blocked, the airflow in your home is restricted.


As your system cools your home, dust parties and other small debris are circulated and become trapped in your air filter. As the filter collects more dirt, air flow slows. When you replace your filter proactively, you don’t notice how a dirty filter can impact your AC. However, as filters become dirty, they create a blockage that can significantly impede the flow of air. This can lead to hot spots around the house, and will put more strain on your HVAC system.

What’s the Purpose of an Air Filter?
You might have considered nixing your air filter altogether. After all, no dirty filter, no filter maintenance.
In addition to reducing the level of dust and particles floating around in your home, filters have one important job: to keep debris from accumulating on your HVAC equipment. When dirt collects on your AC’s coils, your unit loses efficiency and has to work harder to keep up. This can ultimately lead to the AC forming ice, which can damage your compressor and other parts of your HVAC system.
A standard 1-inch air filter provides plenty of protection for your AC unit, but should be changed every 1-3 months, with more frequent changes during the summer.


The thermostat is responsible for determining whether the AC should be off or on. By assessing the surrounding air temperature, it can automatically regulate how much cool air is pushed into your home.
If your thermostat has been imprecisely installed in an area near an air vent, it will judge your home to be cooler than it actually is. This will cause your AC to shut off before all parts of your home have achieved an ambient temperature.


Lots of natural light in the home is a gift, particularly in winter, but between May and Oct..ember, the Austin sun has a reputation for being relentless. If parts of your home receive lots of direct sunlight and you notice those areas getting uncomfortably toasty in the afternoon, there’s likely nothing the matter with your AC or your thermostat placement. You can turn down the air to remedy the situation, however, if you’re looking to limit your energy consumption, we recommend adding blinds, drapes, or both.
Pro Tip: A darker curtain will keep out more light, but will actually trap and radiate heat back into your home. Try a lighter drape to reflect light instead. Choose a tightly-woven fabric or something with a lining.


Your home’s insulation keeps warm air out and cold air in. If your insulation is old and worn, you’ll experience hot spots in your home where heat can easily get in.
Uneven cooling caused by faulty insulation is particularly common in rooms above the garage. If the room above your garage is the only place in the home that experiences consistent cooling or heating issues, the problem likely lies with your insulation, not your AC.


Most homeowners unknowingly experience some level of energy loss from small duct leaks, but issues such as uneven cooling, reduced airflow, or an AC that’s constantly running could be a symptom of a larger problem. AC air leaks affect the everyday comfort you want to experience in your home, and can additionally create a big dent in your wallet, so it’s important to get a professional assessment as soon as possible.


If you notice that your home consistently has hot and cold spots, the issue might be the construction. Whether you’ve always experienced temperature fluctuations in your home or you’ve recently found this to be an issue after building an addition, your home may not be entirely compatible with your HVAC’s assembly. You might be experiencing cooling issues related to the layout of your home if you live in a multi-level home, you have high ceilings, or your home has new additions.
Rather than turning down your AC or closing certain vents in order to try to remedy the irregular conditions of your home, consider a more effective solution such as HVAC zoning or mini-split installation.

Learn more about professional solutions for uneven cooling.