Everything You Need to Know About Your Furnace Filter

Maintaining your HVAC system is crucial for ensuring that it operates efficiently and effectively. One of the most important steps in maintaining your system is regularly changing your air filter. In this blog post, we’ll explore the impact of MERV rating, filter thickness, and frequency of filter changes on furnace pressure drop and airflow, along with the steps to change your filter.

Understanding MERV Rating


MERV rating measures the effectiveness of air filters in capturing particles. The higher the MERV rating, the more effective the filter is in capturing smaller particles. Filters with MERV ratings between 1 and 4 are considered low efficiency, while those with MERV ratings between 5 and 8 are medium efficiency. High-efficiency filters have MERV ratings between 9 and 12, while the highest-rated filters have MERV ratings between 13 and 16. Choosing the right MERV rating depends on the specific needs of your home and HVAC system.

Filter Thickness and Pressure Drop

 The thickness of an air filter impacts its surface area, which can affect furnace pressure drop and airflow. A thicker filter, such as a 4-inch filter, generally has a lower pressure drop compared to a thinner filter, as it has more surface area to allow for airflow. A thinner filter may also restrict airflow, leading to increased energy bills. A thicker filter, such as a 4-inch filter, will generally allow for more airflow, as long as it is the same MERV rating while still capturing the same amount of particles. It’s important to consult with an HVAC professional to choose the right filter thickness and MERV rating for your specific system.

Frequency of Filter Changes

 The frequency of filter changes depends on several factors, including the type of filter, MERV rating, filter thickness, and the number of occupants in your home. As a general rule, it’s recommended to check your filter every 30 days and change it every 60 to 90 days. If you have pets or allergies, you may need to change the filter more frequently. Regularly changing your air filter helps maintain good air quality and prevent clogging that can lead to increased furnace pressure drop and reduced airflow.

How to Change Your Filter

Changing your air filter is a simple process that can be done in a few steps. First, turn off your HVAC system to prevent any dust or debris from being circulated through your home. Locate the filter and remove it from its housing. Check the filter for signs of damage or clogging, and replace it with a new filter of the same size and MERV rating. Make sure to install the filter in the correct orientation and close the filter housing securely. Finally, turn your HVAC system back on and enjoy improved air quality and system efficiency.

In conclusion, understanding the impact of MERV rating, filter thickness, and frequency of filter changes on furnace pressure drop and airflow is essential in maintaining an efficient and effective HVAC system. Regularly changing your air filter and consulting with an HVAC professional can help you select the right filter for your specific system and maintain good air quality in your home. Follow these steps to change your filter and improve your system’s efficiency and air quality.

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