The Ultimate Guide to Furnace Filter Sizes for Allergy Sufferers

If you suffer from allergies or asthma, you know how vital clean air is to your health. Your home's furnace filter is a powerful weapon to help reduce allergens and toxins in the

The Importance of Choosing the Right Furnace Filter Size

Choosing the right furnace filter size is crucial because the wrong size can lead to a decrease in indoor air quality and even cause your furnace to malfunction. If you have an improperly sized filter, it won't fit correctly into the filter slot, leaving gaps around the edges for dirty air to bypass the filter, reducing its efficiency.

When selecting a furnace filter size, make sure to follow the manufacturer's instructions or consult with an HVAC professional for the appropriate size. Installing a filter that is too small can cause it to become overloaded with debris and restrict airflow, resulting in decreased efficiency and increased energy bills. Meanwhile, a filter that is too big will not fit correctly and can cause the furnace to malfunction.

Using the proper filter size also plays a significant role in reducing allergies and improving indoor air quality. The right size will trap harmful particles such as pollen, pet dander, and dust, and prevent them from circulating in the air you breathe. This, in turn, can help alleviate allergy symptoms, including sneezing, coughing, and watery eyes.

By selecting the right furnace filter size, you can save money on energy bills, improve indoor air quality, and reduce allergic reactions. Remember to follow the manufacturer's instructions or seek professional advice to ensure you're using the appropriate filter size for your furnace.

Understanding MERV Ratings for Furnace Filters

When shopping for a furnace filter, you'll notice a rating called MERV. But what does MERV mean?

MERV stands for Minimum Efficiency Reporting Value. This is a rating system that indicates the effectiveness of a furnace filter at trapping airborne particles. The MERV rating ranges from 1 to 20, with higher numbers indicating better filtration performance.

If you or anyone in your household suffers from allergies, it's important to choose a furnace filter with a higher MERV rating. This will help trap more allergens and improve the indoor air quality in your home.

However, keep in mind that a higher MERV rating also means that the filter may not allow as much air to pass through. This could put additional strain on your furnace and increase your energy bills. Consider finding a balance between filtration efficiency and airflow when choosing a furnace filter.

The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommends a MERV rating of at least 6 for residential homes. However, those with allergies or asthma may want to consider a MERV rating of 8 or higher for maximum filtration.

It's also important to regularly replace your furnace filter, regardless of its MERV rating. As the filter captures more and more particles, it becomes clogged and less effective at filtering the air. Check the manufacturer's instructions for recommended replacement intervals.

Understanding MERV ratings can help you make informed decisions when choosing a furnace filter for your home. Consider your family's needs and consult with a professional to find the best filter option for you.

Common Furnace Filter Sizes and Their Uses

Furnace filters come in a range of sizes, and it's essential to know which size will work best for your home. The filter's size will depend on the model of your furnace and the size of your home. Here are some of the most common furnace filter sizes and their uses:

16x25x1: This size filter is the most commonly used, and it fits most standard furnaces. It is perfect for small to medium-sized homes and removes small allergens like pet dander, dust mites, and pollen.

20x25x1: This size is perfect for larger homes and is also commonly used. It can capture most of the small particles that can cause allergies and is a more efficient version of the 16x25x1 filter.

16x25x4: Working like the 16x25x1 filter, this size can capture more particles and is ideal for larger homes with multiple pets, children and an increased level of outdoor air pollution.

20x25x4: This size filter is a step up from the 20x25x1 and is perfect for the same size of homes with children and more significant sources of pollution such as tobacco smoke or cooking grime.

Ensure that you double-check your furnace's manual before buying a filter. Various brands of furnaces have different filter sizes, and choosing the incorrect size can cause damage to your furnace, which may even void your warranty. Furthermore, if you suffer from allergies, you may need specialized HVAC accessories that could help in reducing pollutants inside the house.

In conclusion, whether you are looking to minimize allergies or improve the life of your furnace, understanding the various filter sizes and their uses is a vital step in achieving the desired outcome. Choose the correct filter size for your home, and enjoy the benefits of fresh, clean air in your home.

Installation Tips for Furnace Filters

Installing a furnace filter is a crucial step in maintaining healthy indoor air quality, especially for allergy sufferers. Here are some installation tips to ensure your furnace filter is functioning at its best:

1. Choose the Right Filter Size

Before making a purchase, be sure to check the size of your current filter, or consult your furnace manufacturer's instructions. Buying the wrong size filter can result in poor air filtration and damage to your HVAC system.

2. Shut Off Power to the Furnace

Before attempting to replace the filter, be sure to turn off power to the furnace. This can typically be done through a switch or breaker located near the furnace.

3. Remove the Old Filter

Remove the old filter by pulling it out from the filter slot. Take note of the direction of the airflow arrow on the old filter to ensure that the new filter is installed correctly.

4. Insert the New Filter

Insert the new filter into the filter slot, following the direction of the airflow arrow. Be sure to align it properly and ensure a snug fit to prevent air leakage.

5. Turn the Power Back On

Once the new filter is properly installed, turn the power back on to the furnace. Run the system for a few minutes and check for any unusual noises or issues.

By following these simple installation tips, you can ensure that your furnace filter is functioning at its best, providing you with clean and healthy indoor air.

Changing Your Furnace Filter: How Often and Why It Matters

While it's important to have the right size furnace filter for your home, it's equally important to change the filter regularly. A dirty filter can not only reduce your furnace's efficiency, but it can also exacerbate allergies and other respiratory issues.

So, how often should you change your furnace filter? It depends on a few factors, such as the type of filter you have and how frequently you use your furnace. As a general rule, it's a good idea to check your filter every month and replace it every 3 months.

But if you have pets or live in a dusty area, you may need to change your filter more frequently. And if you or someone in your household suffers from allergies or asthma, you may want to consider using a HEPA filter and changing it even more frequently.

So why does changing your furnace filter matter? For starters, a dirty filter can restrict airflow, causing your furnace to work harder and use more energy. This can lead to higher utility bills and shortened equipment lifespan.

But more importantly, a dirty filter can also lead to poor air quality in your home. Dust, pollen, pet dander, and other airborne particles can accumulate in the filter and then be circulated throughout your home. This can cause or worsen allergy symptoms, as well as other respiratory issues like coughing, sneezing, and even asthma attacks.

By regularly changing your furnace filter, not only will you improve your furnace's efficiency and save money on your energy bills, but you'll also ensure that the air in your home is clean and healthy for you and your family.

Conclusion: Find the Perfect Furnace Filter for Your Home

Congratulations, you are now an expert on furnace filter sizes! By understanding the importance of choosing the right filter size, you can keep the allergens, dust, and harmful particles out of your home. From MERV ratings to the differences between disposable and reusable filters, you now have all the information you need to make an informed decision when it comes to your home's air quality. Remember to change your filters regularly, and consider investing in a higher MERV rating if you suffer from severe allergies or respiratory issues. By taking care of your furnace filter, you can breathe easier and enjoy a healthier home.

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.