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Illinois Country Living

Doug Rye, licensed architect and the popular host of the "Home Remedies" radio show

Energy Solutions

When Opposites Attract
Dealing with the differences in temperature

I bet the first thought that you had when you read the title of this column was about marriage. Well, never fear, guys! That’s not the topic as this monthly column is always about energy efficiency.

I received several complimentary comments about the December column, which taught you about Delta T and the driving force. You can review that column on the magazine’s Web site - At the risk of ruining a good thing, I want to go a little further with that topic because of its importance when analyzing the energy usage of a house. If you can understand these two columns, you might be ready to graduate to energy efficiency 201.

First, let’s do a little review about the Delta T. Remember you learned how warm air tries to get to the cold air until the temperatures are equal. This difference in temperatures between the warm location and the cold location is called a Delta T. You also learned how humid air tries to get to drier air until they are equal. And, hopefully, by now, you have a better understanding of why some houses have “sweaty” windows and some have areas where mold and mildew are present.

A week before I wrote this current column, a dry cold front came from the northwest and collided with a large mass of warm, humid air. As a result, tornadoes developed, which destroyed hundreds of houses in Arkansas and neighboring states. Tragically, numerous lives were also lost. That is an example of a Delta T and driving force that we all could do without. By the way, if you know of families whose homes were destroyed and plan to rebuild, ask them to call me at my office at 501-653-7931 and I will send them my new house construction video for free. I want them to build new houses that are super comfortable and super energy efficient. And, yes, I definitely suggest building safe rooms in new homes.

While some Delta T situations are awful, such as those that produced the tornadoes, not all Delta Ts are bad. Parts of the nation received much needed rain from these storms. Our food and water supplies are also dependent on such rain. And if it were not for the Delta T phenomenon, we would have a difficult time cooling our homes in the summer.

Consider this. When the thermostat says cooling is needed, your air conditioning unit sends warm, humid air through the cold coil. The air is cooled, condensation occurs in the coil and then trickles to a drip pan and through a little pipe to the outside of the house. The larger the Delta T, the better this system works.

Geothermal systems, which use ground loops to tap the earth’s constant 58-degree temperature, have an advantage with the Delta T. That’s because a geothermal coil is simply colder than most other air conditioning coils, as it is working from cool ground temperatures and not the hot outside air. A regular air conditioning unit has an outside coil and on a hot summer day, the fan in the outdoor coil is pulling hot outside air across a coil in an effort to cool that coil. I have checked temperatures of that coil on numerous occasions and found it to regularly be more than 115 degrees. You can understand that the heat transfer is better using cold groundwater in a geothermal unit than hot outside air from a standard air conditioning unit.

In addition to your air conditioning units, there are other things in the house that use Delta T in a positive way. Those include refrigerators, clothes dryers and water heaters, among others.

Well, that’s all for the Delta T. I do, however, have to say something about marriage after all. A really kind lady once told a nice young couple that she thought their marriage was made in heaven. The young man replied, “So is thunder and lightning.”

Until next time, stay warm and enjoy the good effects of the Delta T.


More Information:

Doug Rye, the “Doctor of Energy Efficiency-the King of Caulk and Talk” can be heard on several different Illinois radio stations. Or you can go to his Web site at, e-mail him at, or call 888-Doug-Rye or 501-653-7931. You can also sign up for a free newsletter and order his “how to” videotapes.


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Association of Illinois Electric Cooperatives

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