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Q. Two years ago we purchased a 29 year old house. It has a heat pump with forced air. My husband has sinus and some allergy problems. The house gets very dusty. There is a heat vent on the wall above the refrigerator in the kitchen and sometimes the top of the refrigerator has not only dust but some soot on it, and I think it comes from that vent. What is your opinion of getting the air ducts cleaned by a professional, such as BGE or the HVAC company who services our system? Do you think it will help c ut down on the dust?
A. Your house will probably have the second or even the third heat pump heating and cooling your house since the house was built. Heat pumps have a reputation for lasting from 8 to 12 years on average. We don’t yet really know what length of service the newest models will give but I will say they seem to be getting better in all respects as time goes on.
And I’ll bet over the entire life of your home’s air distribution system it has never been cleaned. In fact, when your house was built the notion of aggressively and professionally cleaning residential ductwork was all but unheard of. Times have changed and you need to do some analysis, soul searching and proper planning for the whole effort to yield the type of healthy results you desire.
Normally the dust you see in the ducts is called resident dust which simply means that it just stays there. The force of the distribution fan is such that it can’t dislodge it and it stays put. If you were to increase the fan speed of your air handler y ou would certainly knock some of it loose and you’d notice the difference. But your fan speed is determined by the size of your system so if you haven’t increased the size of your house since it was built, the fan speed will likely be same now as it was 29 years ago.
The grille you see over the refrigerator is most likely a return air grille. That’s one of the locations where the air in the room is returned to the system for reheating or recooling. Airborne particulates will often collect on the leading edges of the grille fins and that's what you see collecting there. Common household dust-- the gray stuff-- is a nasty mix of sloughed human skin, dust mite body parts, pet dander etc. The more people and living things in the house, the greater the dust load will b e.
I wonder about the material you’re calling soot. Do you have any sources of open flame from time to time in the house? Fireplace or gas cooking devices? How about candles-- do you burn candles regularly for any reason? One source of that soot build up can be from those oil-fed plug-in room deoderizers.
I have observed that if one has the ducts cleaned the indoor air quality (IAQ) actually goes down briefly after the cleaning. That’s because the resident dust has been disturbed and the cleaners try to control it from escaping but they can’t get it all.
Obviously regular filter changing at the air handler is something you can do but let me let you in on a little secret-- those filters that come with the systems are more to protect the equipment than protecting you. If the coils in the air handler devel op a coating of dust then heating and cooling transfer will be reduced and the system wont work as well as it should.
I think you can’t go wrong having the ducts cleaned but consider something even more. Consider having one of the newer generations of electronic or high efficiency medium type air filters installed on your system. Doing both will be money well spent and can increase your husband’s respiratory comfort level. For more information on duct cleaning consult the NADCA - National Air Duct Cleaners Association.