I have lots of my auditing customers who ask me about duct cleaning, and if they should do it.  It seems like the only way to get them really clean is with some sort of roto brush, but it also seems like that process is going to possibly do more damage than good.  Obviously this really depends on the duct system and the quality of the craftsmanship, but I was just looking for the Pro's opinions.  Thanks!

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Do you think it's worth cleaning the ducts w/o doing the coil?

For whatever reason, I've never found any dirt in my ducts, not even after new construction. Ditto for coils, maybe a little dust entrained, not even worth cleaning. So much for that industry!

I've seen some A-coils and blower wheels that are downright NASTY. Mostly in older systems that were a rental property at some time.

The failure mechanism for that is often a neglected thin 1" filter that loads up with dust and then is collapsed by the increased pressure drop across it. Then dirty air bypasses the filter, coating the coil, especially in summer when coil is wet with condensation. During heating season, when coil is dry, dust passes between coil fins and some lodges on blower wheel blades. That then reduces air flow, leading to a raft of other problems.

Whether any of that is a case for duct cleaning is debatable.

I do not advocate duct cleaning for many of the reasons listed above. There is way too much scare-mongering going on, I suspect mostly by contractors who have bought into a pricey duct cleaning doohickey and now need to make the payments on it.

I do advocate deep (4-5") filters properly installed in a matching filter cabinet and changed as needed, anywhere from 3-12 months, depending on circumstances (lower end of the range if pets are present)

Duct cleaning stands a real change of tearing up flex duct and duct board. If nothing else, insist upon a Ductblaster or similar duct leakage test before and after duct cleaning if any part of the ductwork is located outside of the conditioned envelope.

The only time I will recommend duct cleaning is when it is evident mice and mouse dropping are found in the vents. I also recommend top filtration the furnace can provide along with HRV or ERV system.

I agree that rodent droppings should trigger cleaning. In the case of flex duct, it may be cost effective to replace rather than attempt cleaning.

In the beginning of the HPES program here in Syracuse, the good people sent out  by NY State to teach us what we needed to know about home performance tended to underestimate the value of duct cleaning.  As it turns out, a dozen or so years down the road, now that knowledge and experience have shaped my understanding of a great number of things, I am prepared to reply to Gordon's question thus:  it depends.

Metal ducts are a lot like teeth:  hard, durable, and more or less designed for the life of the system.  Still, few of us would argue that we shouldn't bother to clean our teeth.

What's more, the degree of hygiene that we achieve when cleaning our own pearly whites needs to be backed up by periodic visits to a trained, professional hygienist for a more skillful going-over.  Note that one does not become a professional in dental hygiene by buying a truck and a franchise.

It's simple good housekeeping to vacuum out floor registers when you have them, but sometimes conditions merit a more aggressive approach.  If the contractor you talk to says that cleaning the ducts will increase the energy efficiency of your home, I recommend that you thank him or her for their time and go back to the Yellow Pages.

The people who clean ducts for you or for your client need to know that there is no such thing as a $99 duct cleaning and that annual cleanings are an example wretched excess.  They should also understand that the very term "duct cleaning" is a misnomer:  they are actually doing a "distribution system cleaning," so the question of whether the coil should be cleaned as well is beneath consideration:  of course the coil must be cleaned.  Someone who thinks otherwise might like to snort the dust pan after sweeping the kitchen floor but before emptying its contents into the waste basket.

The value of duct cleaning is calculated by applying an equation that balances the actual condition of the distribution system with the skill and knowledge of the people who are doing the work.  The downside is that (as always) the supply of bona fide technicians is dwarfed by the number of people who are well-meaning but lack true expertise.  There is also a third category of downright crooks. 

The real problem is a familiar one:  how can you or anyone drill down through the advertising and sales pitches to get to the right decision about duct cleaning?  The answer is also a familiar one:  you need to reply upon your own experience, and you must get that experience while listening carefully to those who have already learned from their own mistakes.

It's a steep and winding road to get to the right decision.

What's the equation? How does one measure the variables?


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