Airdrie Air logo
Menu
A Multi-story Home with Cooling icons and arrows Above the Upper Level

Why Upper Floors Are Often Hotter in Summer

Every home is unique. Factors such as ductwork design and installation, wall and attic insulation, window efficiency, and overall heat load all effect cooling performance. In multi-story homes, it is common for the second and third floors to be warmer than the main floor due to the natural tendency of heat to rise.

Before trying the recommendations below, ensure the following basic maintenance items have been completed:

 
  • Replace or clean your furnace air filter.
  • Make sure the outdoor air conditioning unit is clean and free of debris, cottonwood fluff, and dirt.
  • Close all basement supply air vents.
  • Close the humidifier bypass damper and turn the humidistat to the OFF position.
 

Keep in mind that because your HVAC system is typically located in the basement, it must remove warm air from upper floors while delivering cooled air throughout the home. This often requires the system to work harder to maintain consistent temperatures on higher levels.

Ways to Improve Cooling on the Second or Third Floor

1. Check Return Airflow
Using a tissue or Kleenex, verify that all return air vents are drawing air back to the furnace while the furnace fan is running. The tissue should be pulled toward the return grille.
If a return vent has little or no suction, warm air cannot effectively return to the system for cooling. In some cases, this may be the result of improper duct installation during construction. If you suspect a problem, contact us for an inspection and consultation.

2. Run the Furnace Fan Continuously
Change the thermostat fan setting from Auto to On.
Running the fan continuously during hot weather helps circulate air throughout the home, reducing temperature differences between floors and creating more consistent comfort.

3. Reduce Solar Heat Gain
Limit the amount of heat entering your home by:

 
  • Closing blinds, curtains, and shades during the hottest parts of the day.
  • Installing reflective window film or tint on sun-exposed windows.
 

4. Consider a Smart Thermostat with Remote Sensors
Thermostats such as the Honeywell T10+ or Ecobee can use remote temperature sensors placed in specific rooms.
By monitoring the temperature in a warmer upstairs room, the system may provide improved cooling where it is needed most. Keep in mind that this may result in cooler temperatures elsewhere in the home.

5. Evaluate Basement Return Air Vents
In some open-concept homes without basement doors, covering basement return air vents may improve comfort.
Excessively cold return air reaching the evaporator coil can affect system performance and may contribute to expansion valve (TXV) operation issues caused by low superheat conditions.

6. Adjust Supply Air Registers
To encourage more airflow to upper levels, try the following register settings:

 
  • Basement: 100% closed.
  • Main floor: approximately 50% closed.
  • Upper floors: 100% open.
 

Monitor comfort levels and make adjustments as needed.

7. Test Closing Bedroom Doors
Try closing bedroom doors during the hottest part of the day.
Since warm air rises and cool air naturally falls, open doorways can allow cooled air to migrate to lower levels, reducing cooling effectiveness on upper floors.

More Extensive Solutions for Persistent Hot Upper Floors

If the above adjustments do not provide sufficient improvement, consider the following upgrades:

1. Improve Attic Insulation and Ventilation

 
  • Inspect attic insulation levels and add insulation where needed.
  • Ensure attic ventilation is adequate.
  • Additional roof vents may improve heat removal from the attic space.
 

2. Upgrade Ductwork
If accessible, undersized ductwork may need to be enlarged to deliver more airflow to problem areas.

3. Install Reflective Window Film
Reflective window tint can significantly reduce solar heat gain and improve indoor comfort.

4. Insulate Accessible Ductwork
Properly insulating ductwork located in attics, garages, or other unconditioned spaces can reduce energy loss and improve cooling performance.

5. Assess Window Efficiency
Older windows can lose insulating value over time and may allow excessive heat transfer into the home.
If your windows are aging or underperforming, consider having them evaluated by a qualified window specialist to determine whether repair or replacement would improve comfort and efficiency.