Ask the Architect

Keeping indoor air clean


Q. Every winter I get terrible colds, and this year I got a postcard from a company that cleans air conditioning ducts. Does this help? I’m concerned about stirring up more dust. What else can I do except buy one of those portable air cleaners?

A. These days, with all the requirements for home energy savings, air-tight homes and pressurized air testing, homes are much more likely to have impurities in the air. Homes used to be built with alkali-laden plaster, which mold couldn’t live on. People wore sweaters, because windows leaked cold air and homes were cooler. It seems that modern materials and methods actually brought on more sickness.
The paper backing on gypsum wallboard provides an excellent place in a dark wall cavity for mold spores to live. Inert, sprayed-in foam does help, but most people are intimidated by the cost. Carpets gather dust and, when vacuumed, may release more impurities into the air.
Cleaning hard-walled metal air ducts is a good idea after a couple of years of continuous use. If you only use the system in midsummer heat spells, the main reason to clean the ducts is because dust settles there and adheres to the sides of the air ducts. Spores and other mold prosper in the layers of dust, and can remain inactive until moisture is present, which is why, at certain times of the year, condensation from cold meeting warm air allows the mold to develop.
You should be aware that some air conditioning companies make life easier for themselves by putting in flexible, soft, round duct, which comprises an inner lining of foil attached to a wire spiral frame covered with a thin layer of fiberglass insulation and a plastic sheeting cover. The system installation costs less if the installer passes on the savings to you, and is simpler to install. By simpler, I mean that duct tape is used instead of mechanical fastening with bends of metal and screws.

Unfortunately, you can’t clean flex duct, since the devices used to clean duct apply pressure, with vacuum and scraping techniques that will destroy your flex duct and render your system useless. You should consider cleaning the main “trunks,” which are probably made of metal duct. Duct cleaning is the first step to better breathing in the home. Then, after cleaning, have a reliable mechanical contractor install a filter in your central air conditioning unit, so you have “in-line” filtration.
Ask about the different types of filter systems, such as an electronic, static-type unit that catches dust like a magnet, and also how often the filter requires cleaning or replacement. Don’t just look for the lowest-priced unit, since the maintenance or replacement of the filter may be much more than the savings. With the electrostatic filter, you may be able to simply wash the filter and put it back. Once the filter is installed, you won’t require the portable type, and you should breathe easier, which is nothing to sneeze at.

© 2024 Monte Leeper. Readers are encouraged to send questions to, with “Herald question” in the subject line, or to Herald Homes, 2 Endo Blvd., Garden City, NY 11530, Attn: Monte Leeper, architect.