How Often Should You Replace Your Furnace Filter in Lawrence’s Climate?

If you’ve ever wondered why your furnace seems to lose steam midway through the season or your home feels a little dustier than usual, your furnace filter could be the reason. It’s one of the smallest parts of your HVAC system, but it has one of the biggest jobs—protecting your furnace and improving your indoor air quality. In Lawrence, Indiana, where we swing from humid summers to cold, dusty winters, knowing how often to change your furnace filter can save you energy, money, and a lot of sneezing.

In this blog, we’ll break down how filters work, how often to replace them, and what type of air filter is best for your home. It may not be the one that you’re using!

Why Furnace Filters Get Dirty Fast

Your furnace filter acts like a shield for your heating system, catching dust, dirt, and other airborne particles before they reach sensitive internal components like the blower compartment or heat exchanger. The dirtier that filter gets, the harder your system has to work to pull air through—restricting airflow, lowering efficiency, and putting extra wear on parts that can lead to costly repairs later on.

Here are a few reasons furnace filters in Lawrence homes tend to get dirty faster than you might expect:

• Lawrence’s Air Quality and Weather: Between normal road traffic, ongoing construction, and plenty of windy days, outdoor dust and fine debris easily make their way indoors. Add in the pollen-heavy spring and fall seasons, and it’s no surprise that air filters in Lawrence homes fill up faster.
• Pets: Dog and cat hair, pet dander, and the dust kicked up from foot traffic all end up circulating through your air return vent. Even one pet can clog a furnace filter in half the normal time.
• Year-Round HVAC Use: In Indiana, your HVAC system rarely gets a break. Between heating in the winter and cooling in the summer, your furnace fan runs almost constantly—pulling in more dust mites, dirt, and other airborne particles.
• Indoor Activities: Everyday life adds more contaminants than most people realize. Cooking, cleaning sprays, candles, and even laundry detergent release tiny particles that settle in your filter over time, leading to a dirty furnace filter faster than expected.

It’s not uncommon to forget about your air filter—we’ve all been guilty of it at some point. When you go to change your old air filter and see that it’s dark gray or nearly black, you suddenly remember that it’s been a while. A clogged filter might seem small, but it’s really the Achilles’ heel of your furnace.

How Often Should I Replace My Furnace Filter?

The frequency with which you should perform furnace filter replacement depends largely on the filter’s size, material, and MERV rating (Minimum Efficiency Reporting Value). Most furnace filters come in different thicknesses, and their lifespan varies accordingly. Here’s a general guide:

• 1-Inch and 2-Inch Filters: These thinner, standard filters are the most common in residential HVAC systems, but they also fill up quickly. Plan to replace them every 1 to 3 months—especially if you have pets or allergies.
• 3-Inch and 4-Inch Filters: Thicker filters like these can capture finer particles such as pollen, mold spores, and smaller contaminants, lasting 6 to 9 months before needing a new furnace filter.
• 5-Inch and 6-Inch Filters: These are often found in media air cleaners that can be added to your heating or cooling system. They trap finer particles efficiently and typically only need replacement every 9 to 12 months.

Most homes in Lawrence use standard 1-inch or 2-inch HVAC filters, which means you should change your furnace filter roughly every one to three months. If you have pets or anyone in your home struggles with seasonal allergies or respiratory issues, check it about every 30 to 45 days to protect your indoor air quality and keep your system running at peak efficiency.

What Type of Furnace Filter Is Best?

Maybe you’ve always bought the same type of furnace filter your system came with, but there’s actually a wide range of options out there. So how do you know which one is right for your home—and what makes one filter better than another?

There are three main types of filters used in most HVAC systems:

• Disposable Fiberglass Filters: These are the most affordable, but also the least effective. They capture large particles from dust and lint, letting finer particles like pollen and mold spores pass through.
• Pleated Filters: Made from folded synthetic material, these filters trap smaller airborne particles like dust mites and pet dander while still allowing good airflow. They’re a great middle-ground option for most homes.
• Reusable Filters: Also called washable filters, these can be cleaned and reused multiple times. However, they must be dried completely before reinstalling, or they can grow mold and reduce indoor air quality.

When you’re choosing a new furnace filter, you’ll notice something called a MERV rating—short for Minimum Efficiency Reporting Value. It’s a simple way to measure how well a filter can trap particles. A higher MERV rating means it’s going to capture smaller particles.

Filters with a MERV rating between 6–8 handle everyday dust and dirt. MERV 8–11 is ideal for homes with pets or mild allergies—it captures pollen, pet hair, and finer airborne contaminants. MERV 12 and above filters catch even smaller particles like smoke, bacteria, and mold spores, but can restrict airflow if your system isn’t designed for them.

The right filter helps your heating system and cooling system run efficiently, keeps your air ducts cleaner, and protects your home’s air quality. If you don’t feel like your furnace filter is doing its job, it might be time for something new.

How to Replace a Furnace Filter

Performing a furnace filter replacement is one of the easiest ways to help your heating system work properly and keep your home’s air quality healthy. You don’t need to be an expert—just know where your filter is located and follow these steps.

1. Turn Off the System: For safety, shut your HVAC system off at the thermostat before starting. This keeps air from pulling through while you’re changing the filter.
2. Find the Filter Location: Your filter is usually located near the air return vent or inside the blower compartment of the furnace. If you’re unsure, look for your existing filter—it’ll show you exactly where the new one goes.
3. Remove the Old Filter: Slide out the old one carefully to avoid knocking dust loose into your ductwork. If the surface looks dark gray or black, it’s long overdue for a change.
4. Check the Size and Direction: Look at the frame of your existing filter to find the dimensions (for example, 16x25x1). You’ll also see arrows printed on the side—those arrows show the direction of airflow. When installing your new furnace filter, make sure those arrows point toward the furnace or blower motor.
5. Install the New Filter the Correct Way: Slide the new filter in gently, making sure it fits snugly in the slot. It should sit flat and secure without gaps. A properly installed filter will do a better job catching dust, pet hair, and airborne particles before they reach your internal components.
6. Turn Your System Back On: Switch your system back on at the thermostat and listen for steady airflow. If the air sounds smoother or stronger, that means your furnace can now work properly again.
7. Make It a Habit: Regularly changing your filter—about every one to three months—keeps your HVAC system efficient, protects your ductwork, and helps maintain cleaner, healthier indoor air.

If you ever have any questions, you can always look up “inserting a furnace filter correctly,” “furnace filter change instructions,” or “how to change a furnace filter” online. We’re also always available to help!

Filter Changes Are Just One Part of Furnace Maintenance

A furnace filter replacement is a simple, low-cost task, but it’s only one part of keeping your system healthy. Dirty filters are one of the leading causes of furnace breakdowns—and honestly, many of our service calls start with a filter that hasn’t been changed in months. When the filter clogs, it traps heat, strains the blower motor, and even shortens the life of your equipment.

Beyond replacing the filter, your furnace also needs a full furnace maintenance visit once a year. During a professional furnace tune-up, our technicians clean the internal components, check safety systems, and make sure your unit’s airflow and combustion are balanced. Taking care of these simple steps keeps allergens and dust out of your home’s air and helps prevent costly repairs later. So, if you think it’s not always a big deal to skip a furnace filter replacement or two, think again!

Schedule Your Furnace Maintenance in Lawrence With Honest Abe’s

At Honest Abe’s Heating & Cooling, our story started right here in the Indianapolis area, and we’re proud to keep homes across Lawrence safe and comfortable. From neighborhoods like Fort Ben, Geist’s Edge, Indian Lake, and Lanesville to Oaklandon, The Pike, The Ridge, and Sunnyside, our HVAC experts are nearby and ready to help.

If you haven’t installed a new filter yet and you’re due, let this be your reminder! And if your furnace hasn’t received its recommended annual tune-up, we’re ready to schedule when you are. Don’t wait until winter’s in full swing—schedule your furnace maintenance in Lawrence, IN, today and let Honest Abe’s keep your home warm and cozy all season long.