“When was the last time we changed our furnace filter?” Your wife asks.

Furnaces have filters? “Not long ago,” you lie. “I’m pretty sure I changed it a couple of years ago.”

“Oh, okay. It’s probably still good then, right?” She asks.

“Sure,” you say. “But maybe it won’t hurt for me to check it again.”

Don’t worry, you’re not having a senior moment. Many people forget about their furnace filters. In fact, living in a 55+ community suggests that you are very familiar with furnace filters. It’s your kids or grandkids that need the reminders.

But as long as we’re on the subject, let’s talk about your furnace.

Mechanical Room Part 2

Where does my furnace filter go and how often should I replace it?

In your mechanical room, you have a furnace. Usually, to the side of your furnace, is the ducting that brings your air back into the furnace.

Between the furnace, attached to that ducting, there should be a door. It will either be a hinging door or a sliding access. Your air filter goes directly inside of there.

Different filters might have different recommendations on how often they need to be cleaned or replaced. Most recommend that you replace them every 30 days.

The longest I’ve typically seen is 60 days between filter changes.

How does it fit in?

Some contractors expect you to take apart your furnace every time you want to change a filter. We prefer to give you an easy trap door instead.

Depending on configuration of your ducting, you may have different ways of placing a filter. For tighter boxes, where the air flows in from the side, the filter should just slide right in place.

If you have a wider box, where the air comes down from above, before turning into your furnace, there will often be a track in the bottom of the filter box to hold the filter. Slide the filter in place, then you can tilt the filter towards the furnace. The force of the air passing through the filter will keep it in place and doing its job.

Are there any other filters in the home?

Most of the homes in our retirement communities don’t have basements or a second floor. In these homes, there is only one filter, the one next to your furnace inside your mechanical room.

On our homes that do have a loft, we put an extra filter or two in those upper rooms. These can either be in the form of a fold down return-air vent, as shown here. To access it, you simply slide the grips on the top of the vent, and pull it down to replace your filter.

If your loft is one that has a separate HVAC unit in the loft, the filter would be part of that unit. That one is not generally a replaceable filter, but a cleanable filter instead.

What size of filter do I need?

Unfortunately, there isn’t a one size for all occasions. There might be a one-size for most, but the best way to see what size of filter you need, is to pull out the old filter. The size will be printed on the side of that filter.

Also, while most of our filters are about under 1” thick, you can usually buy the larger 2” filters if you choose (with exception to the fold-down return air vents in the bonus rooms).

Helpful thoughts

Before replacing your furnace filter, turn off your furnace. You can do this with your thermostat, or if you look on the side of your furnace, there is a light switch attached. This light switch is actually a power kill switch for your furnace. Simply flip it off before you change your filters, then flip it back on again when you’re finished.

This is nice, because it’s too hard to fight the rushing air when changing filters. If the furnace is running or if it turns on while your changing your filter, you also run the risk of the filter breaking and getting sucked into your furnace fan, or disturbing the filter’s dust and having that recirculate throughout your home.

There’s many configurations for furnace rooms and mechanical rooms. Even among our active adult communities, we have different setups and configurations. So while not everything here will necessarily apply to your home specifically, this should at least give you a better idea of where your filters are, and how to take care of them.