Keeping your home's air filter clean and up-to-date is essential for maintaining good air quality and energy efficiency. Most experts recommend changing the air filter every 90 days or 3 months, although this may vary depending on the location of your home, the presence of pets, and the age of your system and equipment. Vacation homes or vacant homes that don't have much use can usually wait to change filters every 9-12 months. The more you use your home, the more often you need to change the air filter.
Without a clean air filter, your HVAC unit works harder and is prone to more breakdowns. Compared to other DIY home improvement projects, changing air filters is a quick and painless process that can be done in less than an hour. Oven and HVAC filters are especially adept at capturing and trapping airborne contaminants, such as allergens, pet dander, dust, smog, and even mold spores. In general, filters with a MERV 16 rating or lower are considered HVAC system grade filters for residential, commercial, and general hospital use.
When you remove the air filter from the air handling unit, if you hold it close to a light source, you can see if the filter is dirty or clogged; if you can't see the light through the filter, it's definitely time to change it. The ideal is to change your air filter every three months, however, there are certain factors to consider when determining when to change an old filter. If you are particularly concerned about the air quality in your home, make sure you choose the right air filter for your heating system. If you live in a mild climate and only use your air conditioner or heater for a few hours a day, a filter could last the entire season or up to an entire year.
A HEPA filter is extremely efficient, but a significant amount of air pressure is needed to force air through a HEPA filter. Air filters are generally inexpensive, and changing the air filter is a simple task that does not require a professional hand. The longer the filter is in place, the more dirt, dust and allergens are trapped, clogging the filter and decreasing its efficiency. Air filters typically have a MERV (Minimum Efficiency Report Value) that determines the type and size of contaminants against which the filter will act.
If you live in a “smaller house”, your air conditioners and ovens need to pump less air for the same amount of temperature change, which could mean fewer filter changes. Consult your unit documentation to determine the filter size you need and the range of the minimum efficiency report value (MERV) that the furnace should fall into.