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Is Your Home Too Hot This Summer? Check Your Insulation!


Summer is here, and with it come high humidity and stifling heat. As summer temperatures soar, many Atlantans take refuge in their air-conditioned homes. But if you’ve got the AC blasting and you’re still feeling the heat, the problem might not be with your AC. So before you plan to replace an expensive HVAC system, have a look at your insulation! Inadequate insulation can prevent even the most robust AC system from keeping your home cool during a Georgia heat wave.

Why You Need Insulation

As summer heats up, many of us reflexively reach for the thermostat. It makes sense. Your AC system packs a one-two punch, both cooling the air and reducing the humidity. Of course, everyone knows that when the AC is running you should close your windows and doors. Trying to cool your home with hot, humid air steaming in is a sisyphean battle; you’ll never win. But did you know that poor insulation is just as bad as leaving all of your windows and doors wide open?

Most homeowners expect that with their windows and doors closed, the cool air stays in and the hot air stays out. If you have adequate insulation, that’s absolutely correct. But without the right insulation, the heat from outside comes through your walls like an open window.

How Heat Moves

Heat comes into your home through three processes: conduction, radiation, and convection.

Conduction is how heat travels through a solid body, like your walls, window, and roof. As the sun beats down on the outside of your home, the walls and roof heat up. If your home is sufficiently insulated, that heat stays where it is. But if your roof and walls don’t have enough insulation, that heat will conduct through the solid material and heat up the air on the inside of your home.

Radiation is how heat travels from a hot body, like the sun, via visible and invisible radiation. Visible radiation is what we call light. Invisible radiation, like low-wavelength infrared radiation, can also carry heat. Sunlight travels through space as radiation, both visible and invisible, and heats the planet. That radiation can come directly into your home through windows, or it can heat up the outside surfaces of your home, and then the heat is transferred by conduction. Low-wavelength infrared radiation is also how a space heater heats a room, or why your kitchen feels warm when the oven is on.

Convection is how heat is carried by a fluid. In the ase of your home, that fluid is air. As heat from conduction meets the air inside your home, it warms the air. That warm air rises and travels through your home where heats the rooms, and ultimately, it heats you.

How Heat Travels [infographic]

How Insulation Keeps Your Home Cool

Keeping windows and doors closed helps prevent convection. In other words, it keeps hot air from entering your home. But even with the windows and doors shut, conduction can heat your home as your walls and roof heat up. The only way to prevent your home from heating up this way is to insulate your walls and roof.

Insulation is, in the simplest sense, any material that does not conduct heat very well. As the outside of your home heats up, the heat meets your insulation, and it stops right there. Since the insulation does not conduct heat, the heat does not reach the inside of your home.

The effectiveness of insulation is measured in terms of thermal resistance, which is referred to as R-value. The higher the R-value, the less conductive the insulation is, and the more effective it is at preventing heat transfer.

Typically, as the thickness of insulation increases, R-value also increases. The one exception is loose-fill insulation in your attic. As the thickness of the loose-fill insulation increases, it becomes more compacted under its own weight. Compacted insulation has a lower R-value. So when you use loose-fill insulation in an attic, less insulation may actually be more effective. A TrustDALE certified insulation expert can help you to determine the ideal amount of insulation for your attic.

Reflective Barriers

In addition to insulation, many homes use reflective barriers to keep out even more heat. A reflective barrier is not technically insulation. It does not prevent conduction and it has no inherent R-value. Instead, reflective materials increase the effectiveness of your insulation by reflecting radiated heat back out and away from your walls and ceiling. Since the outside of your home is heated by radiation—e.g., sunlight—reflecting the sunlight away from your home reduces the cooling load on your insulation. When less radiant heat reaches your insulation, it is even more effective at keeping out heat from the outdoors.

Insulation Materials

There is a wide variety of insulation materials on the market. The most common are bulky materials like fiberglass, rock and slag wool, cellulose, and natural fibers. These loose, bulky materials have a high R-value. Fiberglass batting has one of the highest R-values of any commonly-used residential insulating material. Rigid foam insulation is another option, especially for areas with less room for insulation. For attics, loose cellulose fiber is a common and effective insulation material, valued for its high R-value and low cost.

To find the ideal insulation solution for your home, contact a TrustDALE certified home insulation expert. They can inspect your home to find the hotspots—no pun intended—where you are lacking insulation. And they can recommend the best insulation solution to keep your home cool in the summer and warm in the winter.