Winter is here and when was the last time you replaced your furnace filter? Most disposable filters should be replaced every three months. It is important to check the manufacturer’s guidelines for your HVAC filter. Since there are different types of filters, how do you choose the right air filter for your furnace? One major important aspect to look at is the filter’s MERV rating.

MERV stands for Minimum Efficiency Reporting Value, which is a rating system designed by the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE). The rating indicates the size of particles the air filter is designed to capture, which ranges from 1 to 20, the larger the number, the better the filter is at catching small particles.

As a general rule of thumb, filters with higher MERV ratings are more effective and improve air quality; however, higher does not always mean the best selection for your home’s HVAC system. Ratings above 16 are typically used in specialized commercial settings where air filtration and quality are critical, i.e. hospitals.

For residential furnaces, filters range from 4 to 12 on the MERV scale. A basic MERV 4 filter will likely be the most inexpensive but won’t catch the smallest particles (such as pet dander and dust mites). If anyone in your household has health or allergy issues, then you may want to consider a high-efficiency filter, MERV 11 or higher. Typically for most households, a MERV 7 or 8 filter might be the right fit for performance and cost.

It is also important to check your HVAC system to make sure you are utilizing the right type of filter for your furnace. The wrong type of filter can cause your furnace to work harder and increase the risk of it breaking down. Therefore, if you would like to use a higher rated filter, you need to ensure your system has a maximum MERV rating.