Measuring for your Filter
When measuring your filter, most sizes are standard. A 16” X 25” filter actually measures slightly smaller usually 15.5” x 24.5”. Some brands may vary slightly. however all fit in the same 16” x 25” cabinet.
When you have a 1” furnace filter, a merv 7-8 or a carbon filter is recommended (changed every 3 months). Why? The higher the merv rating the more difficult it is for your furnace to push the air through. A 1” filter has very little surface area for the air to pass through and less and less air will be able to pass as it becomes dirty. If you decide it is necessary to use a merv 11-13, it is recommended this filter be changed monthly to protect your HVAC equipment from extensively over-working or breaking down.
A 4” filter has more than 400% more surface area than a 1’ thus allowing the air to pass through easily. For this filter, a merv 11 is recommended for the best balance of efficiency and air cleaning properties (change every 3-6 months)
If you utilize a merv 13, it is recommended this be replaced every 2-3 months.
If you choose to utilize a merv 8, this will be the most efficient option for energy consumption and the filter can be effective for 6-8 months.
We do not recommend filters lower than a merv 7 for HVAC equipment. Low merv filters are used primarily as pre-filters or temporary construction filters. They can also be used for fresh air intakes for mechanical rooms or other commercial applications where air quality and equipment protection is not a concern.