All you need to know to select the right filter for your application and to get the optimal performance from your HVAC system
Changing your indoor air filter regularly not only helps to protect your heating cooling systems from premature failure, but it reduces dust and harmful allergens that you and your family breathe. Each filter has a finite life which is determined by your environment and your clean air needs. Some filters are recommended to be changed no later than 30 days, some are rated for 90 days and, even as long as six months. It is important to know what works for your application.
Changing your indoor air filter regularly not only helps to protect your heating cooling systems from premature failure, but it reduces dust and harmful allergens that you and your family breathe. Each filter has a finite life depending on the type of filter and how much dust and other particles are in the air.
Most indoor air filters can be changed every 30 to 90 days depending on where they are being used, the number of hours the A/C actually runs, the amount of dust in your area (dust load), whether you have pets, or if there are smokers in the building among other considerations. Your maintenance technician can help with determining filter change frequency.
HVAC filters should be changed when they are dirty or, on a frequency with which you feel comfortable that the filter is still effectively filter the air. However, assuming your HVAC system is in regular use, it is good practice not to exceed the manufacturer’s recommended duration. Some of our customers change MERV 8 filters every two weeks while others retain the same filter for 90 days or more. How quickly filters become dirty depends on your environment. If you live close to a highway or construction is going on in your area, you might have to change your filter more often. Pets and the number of occupants in your house will affect your indoor air quality. Therefore, a general rule in determining how often you should change your filter is to initially inspect your filter at least once each month to determine if a filter change is necessary. This will help to determine if you should change your filters every 20, 30 60 or 90 days.
Check that your filter has the correct length, width and thickness as specified by the equipment manufacturer. It may also be useful to ask your HVAC technician to verify your filter size since ductwork may have modified which may require a different filter. Your filter should fit snugly into the filter grill slots, loose enough for easy installation and removal but tight enough to prevent vibration or air leaks around the filter.
Follow the direction of the arrow printed on the side of the filter if there is one. The arrow should be pointed in or up depending on the orientation off your air handler air inlet slot. If your filter has no directional arrow or has only one face reinforced with a backing grid, turn the reinforced face towards the air handler. The reinforced face ensures that the filter medium is not drawn into the air handler during operation.
HVAC filters are normally installed in a grille/frame which houses the filter. The industry sometimes specifies the filter by the actual size of the grille (commonly referred to as the nominal size). However, the actual filter must be smaller than the grille to fit into the unit. For example, a 20” X 20” X 1” filter (grille/nominal size) will typically require 19 ½” X 19 ½” x ¾” (actual size) filter. This is sometimes referred to as an undercut.
There is a list of industry sized filters that are generally considered to refer to the size of the filter grille installed on your air handler and not the actual size of the required filter. Unless otherwise stated by the customer when ordering, filter manufacture will make a filter with dimensions smaller than the stated nominal size.
Minimum Efficiency Reporting Value (MERV) is the industry standard mostly used in the USA to measure the efficiency of air filters. MERV classifies the overall effectiveness of air filters. A higher the MERV rating indicates a higher capacity to filter finer particles and blocks more of the finer dust particles and other airborne contaminants from passing through the filter.
The best filter to use depends on your individual preferences, costs and system design. If someone in your household has breathing problems or your dust load is high, it is recommended that you use a filter with a higher MERV rating than the typical MERV 7 or 8 filter. If you have an odor problem, a carbon filter may help. Some air handlers perform more efficiently with filters with lower MERV rating because lower rated filters typically result in a lower pressure drop across the filter. A typical MERV 4 to Merv 8 filter is usually sufficient for most applications provided they are changed frequently.
Yes. Some carbon or charcoal impregnated filters or other specialized designs can help with odor management. Check with your technician or filtration professional for guidance on odor management
Indoor air quality (IAQ) is a measure of the aerosols, gas content, dust load, temperature, and humidity of the air.