Is it Time to Change Your Furnace Filter? Learn How to Determine the Right Furnace Filter Sizes

Is your furnace struggling to keep up with the demands of winter? Are you constantly battling poor air quality in your home? It might be time to change your furnace filter! Many homeowners overlook this important maintenance task, but it could be the key to improving your furnace's efficiency and extending its lifespan.

However, not all furnace filters are created equal! It's important to choose the right size and type of filter to ensure optimal performance. Luckily, determining the correct size is easier than you might think. In this article, we'll guide you through the process and give you all the information you need to make an informed decision about your furnace filter.

Don't let a dirty or incorrect filter drag down your furnace's performance. Keep reading to learn all about furnace filter sizing and start breathing easier in your home today!

Why Changing Your Furnace Filter Is Important

Regular maintenance of your furnace filter is essential for the efficient and effective operation of your heating system. Here are some reasons why you should regularly change your furnace filter:

  • Improved indoor air quality: An old furnace filter can accumulate dust, mold, and other pollutants over time, which can negatively affect the air quality inside your home.
  • Reduced energy costs: A dirty or clogged furnace filter can hinder the airflow in your heating system, causing it to work harder and consume more energy. By replacing your filter regularly, you can lower your energy bills and reduce your carbon footprint.
  • Extended lifespan of your furnace: A clean filter can prolong the life of your furnace by preventing dust and debris from building up inside the system and causing damage.
  • Improved comfort: A clean furnace filter ensures proper airflow throughout your home, resulting in consistent temperatures and improved comfort levels.

It is recommended that you change your furnace filter at least every three months, or more frequently if you have pets or suffer from allergies. By doing so, you can protect your home, your family, and your wallet in the long run.

Understanding the Different Types of Furnace Filters

Furnace filters come in different types, each with unique features and varying efficiencies. Understanding the different types of furnace filters can help you choose the right one for your home and ensure optimal indoor air quality.

1. Fiberglass Filters

Fiberglass filters are the most common and least expensive type of furnace filter. They are made of spun glass and have a flat panel surface. Their main function is to protect the furnace from large particles that can damage the equipment. However, they are not very effective at capturing smaller particles and have a low MERV rating (Minimum Efficiency Reporting Value).

2. Pleated Filters

Pleated filters consist of polyester or cotton that is folded accordion-style to increase the surface area. They are more efficient than fiberglass filters and can capture smaller particles. Pleated filters have a higher MERV rating and can be used for up to three months before replacement.

3. Electrostatic Filters

Electrostatic filters use electrostatically charged fibers to attract and capture particles. They are highly efficient and can capture both large and small particles, including pollen, dust, and pet dander. Electrostatic filters can be washable or disposable, and their MERV rating varies.

4. HEPA Filters

HEPA (High-Efficiency Particulate Air) filters are the most efficient type of furnace filter. They capture a wide range of particles, including bacteria, viruses, and smoke. HEPA filters have a MERV rating of 17-20 and can remove up to 99.97% of airborne particles. However, they are costly and require frequent replacement.

Choosing the right furnace filter depends on your indoor air quality needs, the size of your furnace filter slot, and your budget. Consult with an HVAC professional to determine the best type of furnace filter for your home.

How to Determine the Right Furnace Filter Size

When it comes to selecting the right furnace filter size, there are a few things you need to consider. The first is the size of your furnace. The size of your furnace will determine the size of the filter you need. Most filters are sold in standard sizes, so you'll need to measure your furnace to determine which size filter you need.

The easiest way to measure your furnace is to look at the existing filter. The size of the filter should be printed on the frame. If you can't find the size on the filter, measure the length, width, and depth of the filter slot in your furnace. Be sure to record these measurements in inches as they are usually measured in imperial units.

Once you have the measurements, you can select the appropriate filter size. Keep in mind that different types of filters have different levels of efficiency and lifespan. You may want to consider a higher efficiency filter if you have allergies, pets, or live in an area with high levels of pollution.

It's important to note that using the wrong size filter can cause problems with your furnace. A filter that is too small can allow dirt and debris to circulate through your furnace, while a filter that is too large may not fit properly and could cause air flow problems. Make sure you double-check your measurements and select the right size filter for your furnace.

Overall, selecting the right furnace filter size is an important part of maintaining your HVAC system. It's a simple task that can make a big difference in the health of your home and your family.

Tips for Maintaining Your Furnace Filter

Maintaining your furnace filter is essential for the efficient functioning of your furnace. Here are some tips to make sure your furnace filter is properly maintained:

Set a Schedule: Set a schedule for replacing your furnace filter, as recommended by the manufacturer. This could be every three months, six months or even up to a year. Make sure to mark the dates on your calendar so you don't forget.

Clean the Filter: If you have a reusable filter, make sure to clean it with warm water and soap every month. Allow the filter to dry completely before putting it back in your furnace.

Inspect the Filter: It's a good idea to inspect your filter monthly, even if you have a new one installed. Make sure the filter is not clogged with dirt and debris as this can cause your furnace to work inefficiently.

Replace Regularly: If you have a disposable filter, make sure to replace it regularly. A dirty filter can reduce the efficiency of your furnace and cause it to work harder, leading to higher energy costs.

Check Your HVAC System: It's important to have your HVAC system checked regularly by a professional. This can help identify any potential problems and ensure that your furnace is running efficiently.

By following these tips, you can ensure that your furnace filter is properly maintained and your furnace is running smoothly. This will not only help reduce your energy bills but also extend the life of your furnace. Remember, a well-maintained furnace is a happy furnace!

When to Call a Professional for Furnace Filter Replacement

While changing your furnace filter is a relatively easy task that most homeowners can handle on their own, there are certain situations that may require the help of a professional HVAC technician. Here are some instances where you should consider calling in the experts:

  • Difficulty accessing the furnace filter: Some filters may be located in hard-to-reach areas, such as crawlspaces or attics. Trying to change these filters on your own could put you at risk of injury or further damage to your HVAC system.
  • Frequent filter replacement: If you find yourself replacing your furnace filter more frequently than usual, it could be a sign of an underlying issue with your HVAC system. A professional technician can diagnose the problem and make the necessary repairs to ensure your system is running efficiently.
  • Unusual noises or odors: Strange noises or odors coming from your furnace could be a sign that something is not functioning correctly. In this case, it's best to leave the diagnosis and repair to a professional.
  • Age of HVAC system: If your HVAC system is old and outdated, it may be best to have a professional technician perform regular maintenance and filter changes to ensure your system is running safely and efficiently.

Remember, regular maintenance and filter changes are essential to the longevity and efficiency of your HVAC system. When in doubt, don't hesitate to contact a professional to ensure the proper care of your home's heating and cooling system.


If you want your furnace to work efficiently and provide clean air for your family, changing the filter regularly is a must. You can determine the right furnace filter sizes by checking your furnace manual or consulting an HVAC technician. With the right filter, you can prevent airborne pollutants from circulating in your home, reduce energy consumption, and extend the lifespan of your heating system. Remember that the frequency of replacing the filter depends on many factors, such as the type of filter, the number of occupants in the house, and the amount of pollutants in the air. Stay on top of your furnace maintenance schedule for optimal indoor air quality and comfort!

Frequently Asked Question

It's important to know the size and type of furnace filter you need before replacing it. This is because different furnaces require different sizes of filters. Your brand of furnace may need an electrostatic or media filter of a particular size - so make sure to check your old filter for these details.

Replacing your filter regularly can save you money in the long run. It helps your HVAC system become more efficient, and also keeps the air quality high. So, what are the most common furnace filter sizes?

The most popular furnace filters come in the following dimensions: 10x20, 14x20, 16x24, 18x30, 12x12, 14x24, 16x25, 20x20, 12x20, 14x25, 18x18, 20x24, 12x24, 14x30, 18x20, 20x25, 12x30, 15x20, 18x24, 20x30, 12x36, 16x20, 18x25, 24x24 and 25x25. You can use your existing filter as a reference guide to find the perfect size for your furnace. The filter dimensions should be printed on its frame as length x width x height.

In conclusion, it's important to know your furnace filter size before you replace it. Doing so will improve your HVAC system's efficiency and save you money in the long run. Plus, a clean filter is key to keeping your air quality high.

When it comes to furnace filters, exact size matters. If you get a filter that is too small or too big, air will flow around it instead of through it, meaning not all of the air will be filtered. That's why it's essential to use the right size filter for your HVAC unit.

Here's what you need to know: the size of the air filter is typically listed in the big, bold font on the packaging, which is known as the nominal size. This is a rounded-up whole-number version of the actual size, which is written in the fine print on the filter's frame. That's usually 0.25'-0.5' smaller than the nominal size, and the actual measurements of the filter may vary slightly depending on the brand.

In some cases, less common sizes come true to size, meaning the nominal size is the same as the actual size. When that's the case, it's usually noted with “actual size” in parentheses on the filter's frame.

So, the verdict is in: the answer to the question 'Do furnace filters have to be exact size?' is a resounding yes! Be sure to get the right size air filter for your system to ensure it runs smoothly and that you reap all the benefits your filter has to offer.

Are you looking for the best furnace filter? Look no further! Our team of experts at This Old House Reviews have researched the top five furnace filters on Amazon to help you find the perfect one for your HVAC system. Plus, these products are available at local home centers or online retailers like Amazon.

A great furnace filter can make all the difference. It will keep your HVAC system running smoothly, potentially leading to lower electricity bills and better air quality. That's why we've taken the time to compile a list of the best furnace filters for you.

At the top of our list is the Filtrete furnace air filter. It promises to last up to three months and outperform filters made with fiberglass. Plus, it can capture 64% of airborne particles like pet dander and pollen. This filter also comes with instructions for easy installation on HVAC systems that require filters 20 by 25 by 1 inches in size.

Customers love this furnace filter. They find it easy to install, sturdy, and a great value. However, some customers have faced difficulties with Filtrete’s app.

When choosing a furnace filter, make sure to take into account its size, filtration level, and material. That way, you can get the best filter for your specific needs.

Changing or replacing your furnace filter is one of the best ways to maintain a healthy, efficient HVAC system. But you need to make sure that you're using the right filter for your system. Here's a step-by-step guide to help you pick the perfect one!

First, measure the dimensions of your existing filter. This will tell you the length, width, and depth you need. The easiest way to do this is to look at the existing filter and buy the same size.

Next, you need to choose the right MERV rating. The MERV scale ranges from 1-20 and measures the filter's effectiveness at catching particles in the air. The higher the value, the more effective the filter is at trapping particles, but it also means less airflow.

Now it's time to decide on the type of filter. There are many options available, so take some time to research the best type for your system.

Once you have everything you need, it's time to install the filter in your furnace/air handler slot. Remove the old filter to make room for the new one.

Finally, make sure to replace your filter regularly. If it clogs up with dust and particulate, it can reduce airflow and become ineffective.

Furnace air filters are essential for your heating system. You should replace your filter at least once every three months. So, how do you select the best furnace filter for your needs? Let us help you out!

Generally, furnace filters are made up of a cardboard frame, fiberglass filter, and metal mesh. These materials work together to strengthen the filter and protect your HVAC components from dust and debris. Plus, they also help improve the air quality in your home. Without a filter, your HVAC system could become dirty and its performance would suffer.

As air passes through the furnace filter, it traps and catches any contaminants. If you don't replace or clean your filter regularly, it can obstruct airflow and cause damage to your HVAC system. In most cases, you should change your furnace filters every three months. However, you may want to replace them more or less often depending on the situation.