I just finished an interesting book,My House is Killing Me, written by Jeffrey C. May. It is subtitled,The Home Guide for Families with Allergies and Asthma.

The book has some intriguing passages — especially for those who sell or service gas-forced air heating or central air conditioning equipment.

“I feel very strongly that people with allergies and asthma should not live in homes with forced-air heating,” writes May. “There is just too great a chance for circulation of contaminants.”

Later on in the book he writes, “If someone in your family has such problems [asthma or allergies] and you can choose the kind of system installed in your home, I recommend avoiding hot air heat with central air conditioning.”

Because the overwhelming majority of News readers sell and service forced-air heating systems and central air conditioning, it is a bit unnerving to read that our systems contribute rather than alleviate poor indoor air quality (IAQ).

I asked some contractors to respond to May’s comments, and then asked May to expand on his thoughts.


Steve Hardesty of The Hardesty Team, Oklahoma City, OK, took exception to some of May’s assertions.

“I would say apparently the man does not know of all the systems available to provide quality indoor environments,” Hardesty commented. “You can bring in fresh air through the heating and or cooling system that is filtered and cleaned with a central heating and cooling system. All systems must be properly installed, maintained, and cleaned to prevent the possibility of inducing any contaminants into the air.”

Eric Knaack, residential service manager for Isaac Heating & Air Conditioning, Rochester, NY, said, “This [blame on circulation] would be true if the forced-air system were the source of the contaminants, but it is not. It is merely adding to the circulation of the particles.”

Jim Hussey of Marina Mechanical, San Leandro, CA, and current chairman of the Air Conditioning Contractors of America (ACCA), added, “The single biggest contributor to the forced air/mold problem is inadequate filtration and inferior return-air systems. Forced-air systems that have leaking return systems or bare wood return plenums, introduce negative pressure into wall cavities that subsequently draw exterior moisture/humidity through failed vapor barriers.

“Forced-air systems that are designed, sized, installed, and maintained properly [to the standards found in Manual J-8 and Manual D] avoid mold problems and provide environments that are healthy and comfortable.”


After examining the contractors’ comments, May responded this way:

“I am aware of the fact that fresh air can be introduced by mechanical systems through any number of ways; however, my goal is not to reduce the concentration of bioaerosol pollutants through dilution,” he answered. “Rather, my goal is to eliminate their production and dissemination. Unfortunately, air conveyance systems are the prime disseminators.

“The main problems I see with furnace-A/C installations include inadequate and leaky filtration, blower cabinets lacking bottoms, leaky and filthy duct systems” — in new homes soiled due to construction dust and in older homes due to neglect — “and inaccessibility of equipment for servicing” — due to flaws in construction, installation, and manufacturers’ design.

“In addition, ducts are often installed in areas — such as basements close to concrete and crawl spaces — where temperature differentials lead to high relative humidity within, creating conditions that inevitably yield microbial growth in the dust.”

Hardesty, however, concluded, “I don’t believe the answer is moving backwards in time and sacrificing the comforts that we have become accustomed to, but having the proper information and training to provide people with solutions.”

What’s your opinion?

Hall is business management editor. He can be reached at 734-542-6214; 734-542-6215 (fax); johnhall@achrnews.com (e-mail).

Publication date: 06/17/2002