Cooling off the hottest place on earth

E000392Based on the comments I have received from some of our ­readers, you have enjoyed the last few columns about energy origination and the ways that heat travels from one location to another.

I have included some of these same principles in my energy efficiency presen­tations, and they have also been well received. So, once again ­remember that all energy comes from the sun, heat always moves toward cold and moisture always moves toward dry. In the next few issues, we will discuss how these principles affect the comfort and utility bills of your house. More importantly, we will give you solutions.

Since July is usually pretty cotton-picking hot, I thought we would start with the hottest location in the house, which would be the attic. In my seminars, I often ask, “Where is the hottest place in America on a hot summer day?” Someone may answer, “Death Valley, California.” Well that is a good answer, but many attics are hotter. I then ask them, “Where is the one location you would not want to put the AC cooling unit or ductwork?” It usually gets really quiet at this time. Someone finally answers, “In the attic.” Well, let me ask you how you would like to sit in your attic on a hot summer day and try to make homemade ice cream? We would probably keel over before the ice cream was ready.

It is now obvious to you that the attic may not be a good place for the AC cooling system. It may also now be obvious to you that a substantial part of your heating and cooling bill is related to the ­location of the heating and cooling system. So why is the AC unit and ductwork still located in the attic in many of the new houses being built? It is mostly because it is more convenient and no one has demanded change.

Studies have shown that ductwork located in attics and ductwork ­leakage in the attics may be the single ­biggest waster of residential energy. It is ­absolutely unbelievable how much energy could be saved if folks sealed the ductwork and made the attic cooler.

Using our energy principles, how did the attic get so hot, and what are the solutions? Of course it all started at the sun’s radiant heat. The heat rays left the sun, traveled through space and headed straight toward earth. Some of the rays were absorbed or reflected by the atmosphere and clouds. And some were absorbed into the earth, trees and water, etc. Many of the rays hit the roofs and gable ends of houses. The roofing can get super hot really fast. The hot roof becomes a heat radiator and heats the attic by radiation and convection. All adjacent materials such as ­insulation, ductwork and framing materials absorb the heat and get hotter and hotter until the rays of the sun are reduced in some way. Much of the heat is absorbed by the insulation, keeping it from reaching the cooler living space, which is good.

Possible solutions to make your attic cooler:

1. If the ductwork is in the attic, the best answer, in most cases, is to spray the entire sloped roof ­decking and gables with foam, which encapsulates the entire attic space. By doing this, there is no longer an attic at all. It is now just an odd shaped room upstairs and the ductwork is now inside the conditioned space. In this case, the ductwork leakage does not matter as much because it is inside the house anyway.

2. If the ductwork is in the attic but costs prevent you from doing the No. 1 solution, you can do what many others have done in the past: make sure that the ductwork leaks are sealed and add insulation [my preference is cellulose] until you have a total insulation depth of about 13 inches. If possible, cover the ductwork with insulation.

3. Another solution, that you may do yourself, is to properly install a radiant barrier on the bottom or between the sloped roof rafters. This can lower the attic temperature by 20 to 30 degrees on a summer day. Installing or rolling out radiant barrier on top of your existing insulation is not a proper installation method. Doing so will render a negative effect.

4. If your ductwork is not in the attic, you may only need to add cellulose insulation.

Yep, at least one of these solutions will be the answer for you when it is so cotton-picking hot. Call me at the office if you have questions.


Doug Rye can be heard on several dif­ferent Illinois radio stations. You can go to Doug Rye’s Web site at, e-mail him at, or call 501-653-7931.