As an HVAC expert, I am often asked about the frequency of changing furnace filters. The general recommendation is to change the furnace filter every 90 days or 3 months. However, this can vary depending on factors such as the location of your home, the presence of pets, and the age of your system and equipment. In homes with pets, it is recommended to change the filter every 60 days or every 2 months.
For homes with multiple pets or individuals with allergies or respiratory conditions, it is best to change the filter every 20 to 45 days. Vacation homes or homes that are not frequently used can wait longer to change filters, typically every 9 to 12 months. The general rule is that the more you use your home, the more often you should change your air filter. Even in the summer months, it is important to replace the filter at least every three months. If you struggle to remember when to change your filter, a good rule of thumb is to do so every time the seasons change. However, it is important to note that if your air filter is made of fiberglass, which is a relatively poor quality material, it should be changed once every 30 days.
On the other hand, if you have a more expensive pleated filter, it may last longer and only need to be replaced every three to six months. The best way to determine how often your air filter needs to be changed is by visually inspecting it every month. After a few months, you will have a better understanding of how quickly it becomes dirty. It is important to reassess the frequency of changing your filter if you get a new pet or if there has been poor outdoor air quality. Filters with folds, such as the Honeywell ultra-efficient filter, have more surface area to trap dust and therefore require less frequent changes, typically every 90 days.
However, using an air filter with a MERV rating higher than what is recommended by your furnace or air conditioner manufacturer can actually affect its performance. If you notice that your furniture becomes dirty soon after cleaning it, it may be a sign that your filter is clogged and no longer effectively removing dust from the air. Filters play a crucial role in the overall operation of your furnace and can greatly impact the air quality in your home. Filters with higher MERV values are denser, which means your furnace has to work harder to pass air through them. Not all furnaces are powerful enough to do so.
The Minimum Efficiency Reporting Value (MERV) rating of an air filter measures how effectively it prevents dust and other contaminants from passing through and reaching the air stream. To make it easier to remember when to change your filter, many furnace manufacturers recommend doing so at the start of each new season. If your furnace can handle it, I recommend using a filter with a MERV rating of 12, such as the Nordic Pure Filter. Filters with higher MERV values are more effective at trapping small particles compared to those with lower ratings. The deeper the folds of the filter, the more surface area it has to collect airborne particles, which means it may not clog as quickly as a flat filter.
When deciding how often to change your furnace filter, there are several factors to consider and many filter manufacturers provide recommendations for their specific products. As a general rule, for those who suffer from allergies, it is best to change the furnace filter every 30 to 60 days. Filters receive a Minimum Efficiency Notification Value (MERV) rating on a scale of 1 to 16, with ratings between 6 and 12 being ideal for residential furnaces. In general, filters with a MERV rating of 16 or lower are considered suitable for HVAC systems in residential, commercial, and hospital settings.
