Damage to the HVAC System This can cause these parts to fail, leading to costly repairs or even the need for a full system replacement. 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.
If the air filter is too large, it will cause the system to run slowly and reduce the efficiency of the filtration process. This requires more energy to run during the day and will increase your bills.
If the filter is missing or unmarked, measure the filter slot in your HVAC system for these dimensions. Always ensure the size matches exactly, as even slight differences can affect filtration efficiency and system performance.
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.
You can totally cut it to size. Just make sure you don't cut into the actual filter media because that's the part doing all the hard work. Folding might block airflow and make your HVAC work harder, not cooler. I had a buddy who did the same thing, and a quick trim did the trick.
If you suspect you've been using the wrong size air filter, take the following steps to minimize any potential damage: Replace the filter immediately: Swap out the incorrect filter with the right size to ensure optimal airflow and filtration.
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.
The blower fan in your HVAC system may not be able to handle anything stronger than MERV 12. A filter that blocks airflow will raise the air pressure in the HVAC ventilation system, which can damage ducts and even the AC and heater.
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 filter must fit snugly in your furnace.
A filter that's too small will leave space where debris and particles can enter; a filter that's too large won't fit in the slot. You can't trim it down, either, since that will create gaps that allow things like dust, dander, pollen, and indoor air contaminants to enter.
If your filter is not the right size, either too small or too big, air will flow around the filter rather than through it, and as a result—not all of the air will get filtered. For many people, air filtration is a confusing, seldom talked about topic where questions often go unasked and unanswered.
The most common problem you will face with a backwards facing filter is simple inefficiency. If your furnace is forced to blow air through the non-porous end of a filter, it will take more energy to do so. The blower will be overworked and you will pay more money for your heating.
There are Different Filter Sizes
You cannot buy just any furnace filter and expect it to fit. You will need a furnace of a specific length, width, and height in order to replace your current filter. The simplest way to do this is to look at the current filter you have and match the new ones to it.
You can use a 20x25x4 filter instead of a 20x25x5. But it might not securely fit and may not be that efficient.
If an air filter is too big for the slot in your HVAC system, it won't fit properly and may allow unfiltered air to bypass the filter. This can let in dust, allergens, and other particles, reducing indoor air quality. You may also damage an oversized filter when installing it.
Yes, higher MERV filters are more restrictive and reduce airflow.
When the filter doesn't fit in its hole properly, those small particles can move around the filter and lower your air quality. 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.
Your furnace can, technically, run without a filter. However, we strongly recommend you don't run your furnace without a filter for any length of time. With air constantly moving through your furnace and your home, dust and debris can quickly build up, even in a matter of minutes.
Sometimes, a MERV 11 filter may be too restrictive, particularly for older or smaller HVAC systems not designed to handle the increased pressure drop. If you notice that airflow has diminished or your HVAC unit is cycling on and off more frequently, these could be signs that your filter is too restrictive.
Stiffer builds for steadfast seal: 1-inch filters have less material to control, which means the frames are thinner. Thin frames have flimsy seals which let through unfiltered air, defeating the purpose of your filter. 5-inch frames are thicker and fit into the furnace more seamlessly.
This extra depth gives the filter more room for airflow. That means that as the filter collects dirt and other debris from your air, it won't restrict the airflow in your furnace as much. This prevents damage to the furnace and gives the filter itself a longer lifespan.
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.