Air Duct Cleaning, Furnace Filters and Air Quality Q&A

Monica Ussin | May 23, 2003 | Air Quality, Cleaning Tips, Posts | No Comments

Question:
We know so little – can you help?
Is duct cleaning really a help in home air quality? Quote was for $325 for a medium two-story house.

Any information on a company called (name withheld) out of Georgia. The sale rep makes claims for a CAP100 inline filtration system. Efficiency of up to 97% at 6 microns (up to 97% ???). It pictures a 1 inch pre filter with a 5 inch Final filter (BioPleat tm). Is this just a fancy looking furnace filter that costs a lot or is it really better than the 3M 3-month 1-inch filter (about $10.00) or some other such regular filter?

What effect do these larger 5-6 inch filters have on the blower motor of the furnace? Any problems there?

Rob B – Bangor

Answer: Hi Ron,

There are a few things you need to consider before deciding to have your ductwork cleaned.

First, you need to determine what kind of material your ducting system is made of. If it is not encapsulated there is no point in cleaning it. The reason is that you will stir up the insulation because it is not sealed. If you feel the inside of the ductwork and it feels soft you are feeling the insulation and it is probably not encapsulated so you should not have them cleaned. The reason for this is most companies will come in with rotary brushes to scrape and remove any of the dirt and debris that is clinging to the ducting. If the ductwork is not encapsulated the brushes will stir up the insulation and you will be worse off than before you started. If your ducting is encapsulated the inside will feel hard.

Next and most important, you should only consider duct-cleaning companies that are N.A.D.C.A. certified. This is the National Air Duct Cleaners Association. To be a member they will need to pass certain tests and the people doing the work are specially trained and cannot perform any work with the company until they have passed the special courses. N.A.D.C.A. companies will insure they are serious about the work and not in it for the short run.

Of course, I always recommend getting references from previous customers so you can call them and talk to them if you wish. Also, it is always worth it to call the Better Business Bureau to see if there are any recent complaints against the company.

Normally, you only need to clean your ductwork every 5 years or so. If they are dirty cleaning the ductwork will be very helpful.

Concerning the furnace filters they are describing, determine if it is a cleanable filter or you need to replace it. We recommend the furnace filters that are electrostatic that you can periodically clean every 2 to 4 months and you never have to replace them. They are usually one inch thick. The efficiency ratings they give you are very good if they really do perform to those levels. You normally should look for a filter that can remove between 75 to 85 percent of the particulates down to as small as 1 to 1.5 micron. Keep in mind, the reason you cannot remove particles any smaller is because in most cases you would need a Hepa filter to attain these efficiencies and this would result in too much of a strain on the air system. The reason is a Hepa filter is very thick and offers a great deal of resistance to the air movement. You mention they are describing a pre-filter and a final filter. Be careful the furnace filters are not going to shut off the airflow too much by having the two filters. A good furnace filter can remove up to 50% of all of the dust and particles circulating through your ducting. I would ask them what the airflow resistance was when the filter is clean and when it is dirty. The clean airflow resistance should be between 0.1 to 0.5. If it is close to 1.0 or higher it will be too much resistance to your furnace.