Furnace Air Filter replacement frequency
The frequency of replacements depends of a few factors, where you live, unit operation and airborn dust in your home (pets, etc). For optimal performance change your filter every 3 month. Fact is that your filter is more efficient as the dust is lodged in filter however it should be changed when resistance is too high (approx 1" inch wc). Thicker filters have more filtering area and therefore can be changed every 6 month or less depending of usage. In fact thicker air filters have less resistance (approx 1/2 of 1" filters) and will use less fan energy hence saving valuable $$$.
Dirty Filter Clean Filter
Air Filter size and how to determine.
Minimum Efficiency Reporting Value
Minimum efficiency reporting value, commonly known as MERV rating, is a measurement scale designed in 1987 by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) to rate the effectiveness of air filters.
The scale "represents a quantum leap in the precision and accuracy of air-cleaner ratings and allows for improved health, reduced cost and energy efficiency in heating, ventilation and air conditioning (HVAC) design. For example, a HEPA filter is often impractical in central HVAC systems due to the large pressure drop the dense filter material causes. Experiments indicate that less obstructive, medium-efficiency filters of MERV 7 to 13 are almost as effective as true HEPA filters at removing allergens, with much lower associated system and operating costs.
The scale is designed to represent the worst-case performance of a filter when dealing with particles in the range of 0.3 to 10 micrometers. The MERV rating is from 1 to 16. Higher MERV ratings correspond to a greater percentage of particles captured on each pass, with a MERV 16 filter capturing more than 95% of particles over the full range.
Below is a table grouping MERV ratings by particle size:
While the smallest MERV value in each row has no minimum requirement for filtering that row's particle size, it does have stricter requirements for all larger particle sizes than any smaller MERV value. For example, MERV 13 the "0.3–1.0 μm" row has no minimum requirement for removing 0.3–1.0 μm particles (the standard specifies "<75%") but has higher minimum removal percentages of 1.0–3.0 μm, 3.0–10.0 μm, and > 10 μm particles than MERV 12 and all smaller MERV values. All other MERV values on each row do have minimum removal percentages for that row's particle size
MERV rating is the only recognized method of determining filter efficiency , other methods like MPR are proprietary to manufacturers.
Looking for more information on energy savings tips for your home, consult the following links