In 1973, a little less than half of all new single-family homes in the U.S. had mechanical air conditioning. By 2018, according to government statistics, only 7% of new homes lacked it, and in some parts of the country the number of non-AC houses was essentially zero.
The trend will continue. With global temperatures continuing to go up, air conditioning is becoming essential to an increasing number of people. Experts from the Rocky Mountain Institute project that the total number of residential air conditioners will rise from 900 million today to 3.7 billion by mid-century.
Despite the near universal expectation for AC in the U.S., cooling needs across the seven climate zones in the Lower 48 are anything but uniform. Temperature ranges are obviously very different from one region to the next, but so are humidity levels. Houses in Arizona and Florida may experience the same temperature on any given day, but they will be coping with very different moisture levels—one dry and hot, the other muggy and hot. Each presents a different cooling challenge.
Cooling strategies run all the way from a whole-house fan in the attic that flushes out hot indoor air at night to a fully-ducted mechanical system. In some parts of the country, AC is needed on only a few days each year. In others, life is miserable without it.
This survey of residential cooling equipment is an introduction, a look at the basics. There are scores of articles and much more detailed information elsewhere at Green Building Advisor, available by using the search function on GBA’s home page.
As is the case with heating appliances, choosing the right AC equipment begins with an accurate calculation of cooling loads. That takes us back to Manual J, the worksheet developed for HVAC contractors by the Air Conditioning Contractors of…