One of the most important components of any comfort maintenance plan is changing air filters in home HVAC systems. Changing filters keeps allergens, dust and other substances out of your home while helping keep your HVAC system running smoothly. Choosing the Right Filter There are different types of filters, and it is important to know which type to choose when changing air filters in home HVAC systems. The effectiveness of any filter is measured according to its minimum efficiency reporting value (MERV), which rates filters based on the percentage of different size particles the filter captures. HEPA filters typically have a MERV rating between 17 and 20. What this technical mumbo-jumbo boils down to is that HEPA filters remove 99.97 percent of particles bigger than 0.3 micrometers (and trust us, a micrometer is pretty darn small) according to U.S. Department of Energy Standards. The average HVAC system uses filters rated between 3 and 13. Pressure Drop Although many homeowners believe that a better MERV rating offers better filtering when changing air filters in home HVAC systems, filters created from tighter filter media create more backpressure, also known as static pressure or pressure drop, in the HVAC system. This could affect the performance and efficiency of the system, which is why you should choose a filter with a good MERV rating and low pressure drop. Think about it – less performance and efficiency means greater costs for energy, and no one wants to write a bigger check to the utility company because they used the wrong air filter! Thicker-pleated filters are often the best choice, as they provide a good rating and less pressure drop. How Often Should I Change My Filter? How often a filter should be changed depends on many factors. If you were selling your car, could you say specifically how many times the new owner would have to fill the gas tank? Of course not, because it would depend on how many miles the new owner drove the vehicle and in what conditions to determine when those things needed to be done. Your answer would probably be “When the gas gauge says it is empty, so check your gas gauge often.” Check your filters at least once a month; if you notice dirt in the filter, it is time for changing air filters in home HVAC units. Do not wait until the filter is completely dirty, as this reduces the efficiency of the HVAC unit, and, again, less efficiency means more money to your friendly neighborhood utility company. Filter Facts Homes with poorly constructed duct systems or with poor insulation may have dust and allergens even if the HVAC system is equipped with a high MERV-rated filter. For these types of homes, air purifiers that combine a pleated and electronic filter may benefit those with asthma or other allergies. Most contractors do not recommend using permanent washable filters because that type of filter is often associated with high pressure drops. If you need more information about changing air filters in home HVAC units, or want to know more about Spencer AC & Heating, visit our website and connect with us on Twitter, Facebook or LinkedIn!