Why Is My Upstairs Too Hot?

August 4, 2022
Smarthouse technician truck in front of 2 story home

It’s a hot and humid summer day, and you’ve just finished working out in the yard. You walk into the kitchen to grab a cool glass of water and let your air conditioner do its job cooling you down, but as you head upstairs to change your clothes you notice the cool air from your ground level is slowly turning into hot and muggy air as you approach the second floor. What gives? Why would your second floor be so much hotter than the first floor?

This is an unfortunate problem for many homeowners throughout the greater St. Louis area, even when their air conditioning system is working properly! SmartHouse has helped many homeowners address summer comfort issues throughout Ladue, Overland, Richmond Heights, Clayton, Creve Coeur, Kirkwood, Webster Groves, and the rest of the St. Louis area — and here is what you need to know!

What Causes a Hot Second Floor?

When it comes time to cool your home down as the temperatures outside start rising, you lean on your air conditioner to provide the cool air you need. So it would stand to reason that your air conditioner is likely at fault for your hot second floor, right? Unfortunately, the answer isn’t that simple. There are a few reasons your air conditioner may not be reaching your second floor, such as:


Is your thermostat located on the first floor? A thermostat can only get a temperature reading for the area it is located in, so your thermostat may not even know your second floor is turning into a sauna! Since the second floor is more directly affected by the outdoor temperatures and sun beating on the roof, it will require more cooling power

Inadequate Return Ducts 

A very common problem we see in the St. Louis areas is that a ductwork system was installed with either an inadequate return duct, or none at all.  Return ducts bring air from the house back to the air conditioner to be cooled. Without an adequate return function, the second floor becomes a warehouse for the heat that will never find its way back to be cooled.

An Air Conditioner That Is Too Small

Air conditioners that are too small for the rooms in your home may be working overtime to fill your living space, and failing to do so. Even if your air conditioner is brand new and operating at peak condition, if it is undersized it won’t be able to keep up with the setting on your thermostat. This is an ineffective way to cool your entire home, and wastes energy (not to mention money)!

Inadequate Insulation

Where does insulation fit into the mix? Insulation is supposed to prevent that heat from transferring between the outdoors and your indoor living space, especially in key areas like the attic. If your attic insulation has deteriorated, was improperly installed, if there just isn’t enough of it, you could be experiencing a second floor that is much hotter than the ground floor. Furthermore, air leaks in your attic can also allow the summer heat to infiltrate your upstairs living space.

Find the Right Combination of Solutions

There is a difference between finding a solution that will “improve” your home comfort, and finding a “fix” for your hot second floor. Often times, it is a combination of solutions that we find are the best prescription for solving the problem of a hot second floor. Depending on the unique needs of your home, we may recommend combining some of these solutions:

  • Installing a ductless mini split system
  • Adding return ducts, and repairing your ductwork
  • Dividing your existing system into multiple, separately controllable zones.
  • Creating separate comfort zones using multiple ductless mini split air conditioners
  • Removing old insulation, and installing upgraded insulation and air sealing

Rest assured, the SmartHouse team can safely diagnose your home comfort issues, using our years of building science and performance knowledge as well as the many diagnostic tools we utilize in our whole home performance appointments

Are you sweating your hot-upstairs issue? Keep cool this summer — Call or contact us to find a cooling solution fast!