Ronald Duquette Jr., technician for Krutsch Mechanical Services Inc. (Taylor, Mich.), believes that filter changes in commercial rooftop units are an important part of scheduled maintenance. In one instance, they added a light by the thermostat that comes on when the pressure drop across the filter changes significantly.
It is an age-old debate: the proper schedule for changing filters on air-handling units. There is no debate on the necessity to change or clean filters. Actually, there may not even be a debate on when to change or clean filters. The real debate may be in how to get people to change filters.

In a worst-case scenario, if a home or building owner were asked if he or she changes their filters, the answer would be "What filters?" In a best-case scenario, the answer would be "Like clockwork, every 30 days after I pay the utility bill."

In reality, the most common answer falls in between the two scenarios. According to industry recommendations, filter-changing intervals can be based on the pressure drop across the filter. Changes can also be determined by a calendar schedule ranging from every one to six months, or by visual inspection. Frequency of changes also depends on the indoor/outdoor environment and the health of building occupants.

Unfortunately, the task of changing filters often falls upon the shoulders of a person who deems the task unimportant or at the bottom of the list of priorities. Only when a problem occurs or the HVAC equipment stops working do some people finally get the message to inspect and change filters on a regular basis.

One contractor, asked by The NEWS about getting homeowners to change filters on a regular basis, said, "I had a customer who was not getting enough heat out of the furnace while the unit was shutting itself off on high limit. I pulled the plugged filter out and told him that it looked like he hadn't replaced it since the previous Christmas, what with all the tinsel in the filter. He told me it had been two years since he put tinsel on his Christmas tree."

That story was mild compared to this: Brad White of TMP Consulting Engineers (Boston) had been contacted by a homeowner to find the source of low humidity levels in a home with an indoor pool. He found that a leaky, rolling skylight was the culprit. He fixed the problem and the relative humidity settled at 45 percent. He left a box of spare filters and a maintenance schedule with the homeowner.

Ten years later, the homeowner's ex-wife (and current homeowner) complained about high humidity levels. He picked up the story from there. "I go in to meet with the owner, the [building] specialist, the architect, and the grounds person. The home was muggy and there was condensation that November day," said White.

"I went into the mechanical room and the dolly I had left for access was there right where I had left it. The boxes of filters were there with the dates visible, unopened. Uh-oh. My Magnahelic® gauges pegged to the stops.

"I shut down the unit just to open the doors, the pressure was that bad. The filters had never been changed in 10 years. I choked to pull them out. I vacuumed what I could see and put in a fresh set and started the unit. A cloud of dust emerged then dissipated but the window condensation evaporated like an invisible hand and squeegee were drawn across it.

"Giving a homeowner an operation and maintenance manual is useless without telling him or her to read it."

Ten years may not be the record. Steve Ebels of Golden Rule Heating in Falmouth (Mich.) related this story. "Twice this past winter, I encountered blowers that were so bad that I took them out of the house and down to a local car wash to hose them out," he said. "One furnace had a filter in it that obviously hadn't been changed in years (if not decades), the other had no filter at all.

"In talking with the owner at that place, he claimed that in all the time living in the house he had never changed a filter, because he couldn't find one. He figured the system didn't need one and he had lived there for 12 years. It was completely covered over with dust, debris, and cat hair. You literally couldn't see the vanes of the blower wheel.

"When I reinstalled it and the blower came on he asked what the noise was. It was air coming from his registers."


Besides verbally telling a customer about the need to change filters and then putting that message in writing, there are other ways to remind people of the need for regular filter service and maintenance.

First of all, talk to a building owner in terms that will get their attention: cost savings. One HVAC contractor said, "Put a dollar figure on potential savings. It is very powerful when talking to the building owner who is always looking to cut costs."

Terry Lisinski of Technical Maintenance, Medford (N.Y.) agreed. "After hearing of the replacement prices for the most expensive part of the system (compressors), my customers willingly allow me the honor of changing filters, twice a year, once per season," he said. "Plus, filters are only part of a full inspection. All customers must agree to inspections for prompt response. Losing a noninspection customer is no big deal but gaining an inspection type customer is very important."

Steve Nunes of Noon-Air Heating & Air Conditioning (Purvis, Miss.) leaves a visual reminder for customers - a carton of filters.

"When I install a new system, I provide the customer with a one year supply (one case) of MERV 7 or MERV 8 pleated filters to go with their new system," he said. "I tell them to change them every month, and when they write the check for their electric bill, use that as a reminder: a clean filter equals better efficiency which equals lower bills.

"I tell them that when they get down to the last filter in the box, it's time to call me to get the system checked and serviced while it's still under full warranty, and at the same time they will have the offer of a service agreement. And, I will bring them another case of filters at the discounted service agreement price. I send them a postcard to remind them when it comes time.

"Unfortunately, I only have 20 percent that call me for the system check. You can lead a horse to water ..."

Many contractors ensure regular changes by selling service agreements. "Sell them a maintenance contract which includes changing the filters," said one contractor. "Or, sell them a service contract where you fix anything that breaks except for big-ticket items. Emphasize that this extended warranty is void if they don't change the filters."

New technology allows for audio messages in wall thermostats. Building owners are reminded of routine maintenance and filter changes by a digitized message on a thermostat. They can turn off the message but they have at least heard the reminder.

A dirty filter removed from an air-handling unit in a residential apartment complex.
Adding a light to the thermostat can also serve as a good reminder to change filters. Art Grace of Krutsch Mechanical Services Inc. (Taylor, Mich.) added a light to the thermostats in a church he recently worked on. "We added a light by the thermostat that comes on when the pressure drop across the filter changes significantly," Grace said. "Oh, by the way, the rooftop units are four stories up with access behind the stage and would otherwise be forgotten."

Bud Goodman of suggests an e-mail campaign. "If you're lucky enough to get the customer's e-mail address, create a list for "Filter Change Reminder," he said.

"Ensure them their e-mail will not be used for spam or junk, but they may receive an online coupon for tune up specials only available to people on the e-mail list."

Randy Chollar of C&J Air Conditioning & Heating Co. (San Antonio, Texas) is looking to expand on his e-mail idea.

"One of the features we hope to develop with our new Web-based software system is an e-mail reminder sent to our customers to change their filters," he said.

"It should be a simple process through our system, be a benefit to our customers, and at the same time keep our name in front of the customer on a regular basis."

Scott Leverenz has a lot of experience selling and installing filters. He gives advice at his Website ( and also works for Jacobs Heating & Air Conditioning (Portland, Ore.) He described a program that can be used for filter maintenance.

"First, annual planned maintenance includes two visits each year, at which time we also change the filters," he said. "Second, an annual filter only maintenance program: two filter-only visits per year.

"Third, if the client has a media filter, we offer a sign-up program where we will send them 2-3 filters via UPS once each year. We also do this for maintenance customers, above and beyond the regular maintenance investment, and the filters are sold at a discount.

"Fourth, we offer a "Free Filter For Life Program." If the residential customer has a regular 1-inch disposable filter, we offer free furnace filters as long as they have us do the installation, have lived in the same home, and pick them up at our offices, with a maximum of six per year."

As one contractor put it, changing filters is like changing diapers. "Everybody knows they have to do it, they just don't want to do it."

Publication date: 06/19/2006