Key Points
- An undersized or outdated AC can’t cool your home effectively.
- Leaks, poor insulation, and dirty filters waste cool air and strain your system.
- Efficient windows, sealed ducts, and clean filters help keep temps steady.
If you’ve ever noticed your house really heats up in summer—even if you have air conditioning—you’re not alone.
A variety of factors can contribute to your home feeling especially hot in the summer months, from exterior factors to interior ones.
We asked HVAC pros why your house might feel hot in summer, and they had some useful fixes too.
Meet the Expert
- Phil Oliver is the owner of Air Treatment Heating and Cooling in Vienna, Virginia.
- Randy Fuller is the owner at Fuller HVAC in Muscle Shoals, Alabama.
- Elizabeth Shavers is the general manager of HVAC and Plumbing at Oncourse Home Solutions.
Your Air Conditioner Isn’t the Right Size
One of the biggest culprits for a house that’s too hot is having the wrong sized air conditioner. If your air conditioner is too small for your home’s square footage, it won’t have the capacity to cool the whole space.
“Many older homes have systems that were installed decades ago when energy efficiency standards were different, or previous contractors cut corners by installing cheaper, smaller units,” says Phil Oliver, owner at Air Treatment Heating and Cooling.
“If your AC runs constantly but never reaches the set temperature, this is likely your problem.”
To fix it, you may need to consider installing a newer air conditioner that is the right size for your space.
Want more home reno project tips and inspiration? Sign up for our free daily newsletter for the latest how-tos, reno guides, and more!
There’s Inadequate Insulation and Air Sealing
If your home isn’t properly insulated or air sealed, this is another common cause of a hot house—but one that homeowners might not be aware of.
“I regularly find homes with insufficient attic insulation, gaps around windows and doors, and leaky ductwork that can lose 20 to 30% of cooled air before it reaches your living spaces,” Oliver says.
If this is the case, Oliver says this can cause your HVAC system or other air conditioning unit to work overtime, as cool air seeps out of your home and warm air is able to get in.
If you think this might be the cause of your home’s high temperature, Oliver recommends “professional air sealing, insulation upgrades, and duct sealing to restore proper performance.”
The Air Filters Are Dirty
While some issues with your home or air conditioning system might require professional help, there’s one cause of a hot home that’s easy enough to fix yourself—and it’s all-too-common.
Your air conditioner or HVAC has air filters, and over time those can become clogged with dirt, hair, and dust. A dirty condenser coil can also contribute to higher temperatures in your house.
“A dirty air filter restricts airflow, while a dirty condenser coil outside can’t release heat effectively, causing your system to struggle,” Oliver says.
And this isn’t limited to your interior system—if you have an outdoor AC unit, it’s worth giving it a once-over, Oliver says.
“I’ve seen outdoor units so covered in debris and dirt that they’re essentially suffocating.”
The Ducts Are Leaky or Imbalanced
The ductwork throughout your home is essential to ensuring every room in your house is at a reasonable temperature, as it takes the air from the air conditioner and distributes it evenly.
If your ducts are leaking or imbalanced—which is often a result of them being old—it can prevent the cool air from reaching certain parts of your home.
“We often find that a home’s second floor or certain corners stay warm because airflow just isn’t reaching them efficiently,” says Randy Fuller, owner of Fuller HVAC. “Add to that blocked or closed vents, and your AC ends up working overtime without delivering comfort.”
Your Windows Aren’t Energy-Efficient
If your home is hot in the summer, and your air conditioner and ducts are in good condition, it’s possible that your windows aren’t energy-efficient enough to keep the warm are out and the cool air in.
Old windows lack the energy efficiency of new windows, which can especially be a problem in the south-facing areas of your home that get a lot of sunlight in the day.
But replacing your windows isn’t your only option.
“To prevent this, you’ll want to ensure you have energy efficient windows that keep the warm air out, along with good blinds that can help keep out the extra warmth from the sun throughout the day,” says Elizabeth Shavers, general manager of HVAC & Plumbing at Oncourse Home Solutions.
