An improperly sized filter won't capture all pollutants (too small) or restrict airflow (too large), leading to reduced efficiency, higher energy bills, potential system damage, and poorer indoor air quality - which can trigger health problems.
actual size of an air filter can affect filter compatibility if it doesn't fit properly into the HVAC system filter slot. Ensuring the actual size aligns with your HVAC system's requirements, even when the nominal size matches, is important if you want system efficiency, proper filtration, and the best performance.
Usually they round up or down to the nearest inch, so it is less likely that these two filters will fit the same furnace because of the rounding. However, if your filter is close to 20x25x4. 5, and the actual dimensions of the 20x25x5 filter are closer to 20x25x4. 5, than they might fit.
If your filter doesn't fit properly, it can interfere with the flow of air from the system to your home. Your air filter may also get sucked into the system, causing damage. Improper installation of the filter or the absence of a filter allows dust and other debris to build up inside the system.
However, beneficial bacteria only grow as much as food (ammonia/ nitrite) is available. So, increasing your filter size wont change the amount of bacteria you have, only how much you could have. Your filter would also get dirty less often, but only because it is bigger.
You can't really over-filter an aquarium, but it's fairly easy to under-filter one. Most aquarium filters are rated according to how many gallons the aquarium holds.
Just adding a 1 inch pleated filter may be detrimental to your system if it is border line already. The best thing to do is upgrade to a 2 inch filter or even a 4 inch filter. Many cabinets allow for either a 1 inch or a 2 inch filter.
Usually, you can find the diameter by looking for the geometric symbol on the body of the lens - “ø”. The number next to that is the one you need. If you can't find it on your lens though, just take a look at your user manual or the manufacturer's site, and it should be pretty easy to find.
If the filter is too small, it won't cover the entire space and may allow dust and dirt to flow past. If you're not sure what size filter you need, check the manufacturer's specifications or ask your HVAC technician for help choosing the right product.
Going down in thickness by an inch shouldn't be a big deal - for example, you should be able to use a 4-inch filter instead of a 5-inch filter. If you are considering a thicker air filter in order to improve air quality it may be better to focus on the MERV rating.
Fortunately, most 20x25x4 air filters last between six to eight months.
MERV 11 filters are ideal because they are effective at catching small particles, while still allowing enough air to pass through the filter. Using the size categories above, a MERV 11 filter can successfully catch65% of E2 particles (1.0 - 3.0 µm) and 85% of E3 particles (3.0 - 10.0 µm).
You may not need a MERV 11 filter or higher unless you have specific air quality issues or allergies. For the average household, a MERV 8 air filter can be good enough. You'll want to think about factors like how often you want to change your filters and what type of material do you want filtered out of your air.
Damage to the HVAC System
Reduced Efficiency of the System: An improperly sized air filter can create an imbalance in the airflow, which means the system may not operate at its designed efficiency. When the HVAC unit is forced to work harder, it consumes more energy, leading to increased utility bills.
What Is the Most Common Size of Air Filter for a House? The most common size air filter for a house is usually 20 x 20 x 1, but this can vary depending on the specific HVAC system installed.
However, it's worth noting that filters with higher MERV ratings can restrict airflow. While filters rated 13 or below generally don't strain most HVAC systems, those rated above 10 might require professional installation.
If you're switching to a different air filter manufacturer, it's best to use the actual size of your current filter when searching for a replacement. While nominal sizes are standardized, the actual sizes can vary slightly between manufacturers.
Using the wrong size filter reduces efficiency, air quality, and can even damage your HVAC system. You can learn more about the difference between furnace and AC filter sizes here.
UNDERSTANDING FILTER SIZES
Therefore, for example, a 16x25x4 filter is 16 inches long, 25 inches wide, and 4 inches thick. It's important to note that filters with different dimensions are not interchangeable due to variations in frame size and media area.
The filters don't need to fit with an "air tight" seal, but you should be able to easily install and uninstall your filter without a struggle, plus the filter shouldn't be so small that it moves freely within your unit.
How Often Do I Need to Change Out My Air Filter? Generally, most air filter manufacturers and HVAC companies recommend changing your air filter every 90 days, or 3 months. That can change based on where your home is located (ex. dusty, dry climates), if you have any pets, and the age of your system and equipment.
Look at Your Existing Air Filter
If your HVAC system has an air filter, you can look for its size to ensure you can get the right replacement. Most filters have sizes listed on the side in print, including the length, width, and depth in inches. Usually, they're listed in that order.
If the air filter is too large, it will cause the system to run slowly and reduce the efficiency of the filtration process.
Our standard recommendation is as follows: For 1- to 2- inch filters, replace them every 1 to 3 months.
Because it is four times as thick as a 1-inch filter, it has a much greater surface area for catching household pollutants. These larger filters also typically come with higher MERV ratings and can capture more contaminants (e.g., pet dander, smoke, allergens, and bacteria) than a 1-inch filter.