What is Thermal Mass Cooling?

As the cold temperatures of winter go away and you begin anticipating the warmth of the spring and summer season, you likely start realizing it's time to turn your air conditioner on and deal with higher energy bills because of it.

Each time you bump the thermostat down, your HVAC system needs to work that much harder in order to keep your home cool and this increases your energy use as well as the costs associated with it. Fortunately, there's a better way for you to cool your home and lower your energy bill while enjoying a cozy indoor atmosphere - it's called thermal mass cooling.

Days are Hot, Nights are Cool
If you live in an area where the days are hot and the nights are fairly cool, thermal mass could make a substantial dent in your home's cooling load. The mass works like it would in all cases, it will:

  • Absorb heat and light during the day
  • Release the heat after your home cools

Because nighttime is a lot cooler than daytime, you can vent the extra accumulated heat by the thermal mass just by opening up a couple windows and letting it escape.

The perfect thing about this system is that it works great and you don’t need to adjust your home at all. The mass absorbs the heat and releases it like it does in wintertime, but the additional ventilation eliminates the stored heat. You can even get it to work with thermal storage walls and sunspaces. This is a good approach if you live in hot, dry climates like the desert when you experience much cooler nights than days.

Exterior Thermal Walls|
Another method that works great in these types of climates would be exterior thermal walls. You must be thick. How they work is just like with milder climates. The light of the sun will warm the walls and store the heat. It then works its way indoors gradually through the wall to the cool interior. However, if the wall is thick, daytime ends before heat can get indoors.

The temperature outdoors drops below the temperature indoors and the stored heat in the thermal walls will reverse direction and head out towards the outdoors. Heat will travel back and forth in the daytime and nighttime and never actually get inside your home.

A Whole House Fan
Whole house fans can also help with thermal mass cooling. To put it simply, they draw the cool night air in from the outside and blow the warm indoor air outdoors. Whole house fans precool your home during the evening and overnight, allowing you to decrease your AC use during the day.