When to Replace Your Furnace Filter

You’ve probably heard that it’s important to replace your furnace filter, but you might be wondering how often you should do it. Does it depend on the type of furnace you have or the filter you use? Where is the filter furnace, anyway?

With so many questions in mind, the HVAC experts at Evergreen Heating & Cooling have created this helpful guide about furnace filters. Keep reading for valuable insights into maintaining your furnace and keeping your Central Texas home comfortable.

What Does a Furnace Filter Do?

Before diving into when and how to replace your furnace air filter, let’s first understand the crucial role furnace filters have on your HVAC (Heating, Ventilation, and Air Conditioning) system.

The primary function of a furnace filter is to filter air and enhance indoor air quality. It captures and removes a variety of airborne particles, including dust, pollen, pet dander, mold spores, and other contaminants. This filtration process helps to promote proper air flow and keep the air in your home cleaner and healthier to breathe.

A clean furnace filter acts as a barrier that protects your HVAC system’s internal components. It prevents dust and debris from accumulating on key parts such as the blower motor, heat exchanger, and heating coil. By doing so, it extends the lifespan of your heating and cooling equipment and reduces the risk of breakdowns and costly repairs.

Proper airflow is also essential for the efficient operation of your HVAC system. A clean filter allows air to flow freely through the system, ensuring that it operates at peak performance. When the system can “breathe” easily, it consumes less energy, leading to lower energy bills and reduced environmental impact.

Why Does a Furnace Filter Need to Be Replaced?

Over time, furnace air filters become clogged with the particles they capture. When they become too dirty, several problems can arise:

  • Reduced Airflow: A clogged filter restricts the flow of air through your HVAC system, forcing it to work harder to maintain your desired indoor temperature. This can lead to decreased efficiency and increased energy consumption.
  • Poor Air Quality: As the filter gets clogged, it becomes less effective at trapping contaminants, allowing them to circulate in your home’s air. This can worsen indoor air quality, leading to allergies and respiratory issues.
  • Strain on the HVAC System: The added strain of a dirty filter on your furnace can lead to premature wear and tear, potentially resulting in costly repairs or even complete system failure.

What Kind of Furnace Filter Should I Use?

When it comes to choosing the right furnace filter, several options are available, each with different characteristics and MERV (Minimum Efficiency Reporting Value) ratings to consider.

  • Standard Fiberglass Filters (MERV Rating 1-4): These filters are the most basic and budget-friendly option for HVAC systems. They are suitable for capturing larger particles like dust and lint but may not be as effective at trapping smaller allergens or pollutants. You’ll want a fresh filter every 1 to 3 months.
  • Pleated Filters (MERV Rating 5-8): Pleated air filters offer improved filtration compared to fiberglass filters. They are more efficient at capturing smaller particles, including pet dander and mold spores. Pleated filters are a good choice for most households and usually last between 3 to 6 months before requiring a replacement filter.
  • High-Efficiency Filters (MERV Rating 9-12): These filters provide a high level of filtration, making them suitable for homes where air quality is a priority. They can capture fine dust, bacteria, and some allergens effectively. High-efficiency filters typically require replacement every 6 to 12 months.
  • HEPA Filters (MERV Rating 17-20): HEPA (High-Efficiency Particulate Air) filters are among the most efficient filters available. They can capture extremely tiny particles, including viruses and smoke. HEPA filters are often used in specialized settings and require professional installation.

The choice of furnace filter depends on your specific needs and preferences. If you have allergies or respiratory issues, a higher MERV ratings range like a pleated filter or high-efficiency filter may be beneficial. However, it’s essential to ensure that your heating system can accommodate the increased airflow resistance of higher-rated filters, as they can strain the system if not compatible.

How Do I Know What Size Filter to Use?

The easiest way to find your filter size is to examine the existing air filter in your furnace or air handler. Most air filters have the size printed on the frame or edge of the filter. It will be displayed as three dimensions: length, width, and thickness (or depth).

If you don’t have an existing filter or if the size isn’t clearly labeled, you can measure the filter slot or the space where the filter fits. Use a tape measure to measure the length, width, and thickness of the filter slot. Be precise in your measurements, rounding to the nearest fraction of an inch. If you have access to the furnace or HVAC system’s manual, it may contain information about the recommended filter size. Check the manual for specifications related to filter dimensions.

If you’re still unable to find the filter size, contact the manufacturer of the HVAC system or the furnace itself. They should be able to provide you with the correct filter size based on your equipment’s model and specifications.

Remember that the filter size must be an exact match for your furnace system or air handler to ensure a proper fit. Using the wrong size filter can lead to air leaks, poor air quality, and reduced filtration efficiency.

How Do I Replace a Furnace Filter?

Replacing your air filters is a pretty straightforward process. Here’s a step-by-step guide to change a furnace filter:

  • Turn Off the Furnace: Ensure your furnace is switched off to prevent injury or damage.
  • Locate the Filter: Find the filter’s location, which is typically near the return air duct or in the blower compartment. Refer to your furnace’s manual for guidance.
  • Remove the Old Filter: Take out the dirty air filter and dispose of it properly.
  • Install the New Filter: Insert the new furnace filter, making sure it is installed in the correct orientation, usually with the arrow on the side indicating the airflow direction.
  • Close and Secure: Close the filter compartment securely, ensuring there are no gaps or loose parts.
  • Turn On the Furnace: Finally, turn your furnace back on and enjoy improved air quality and system efficiency courtesy of your new air filter.

Call Evergreen for All Your Furnace Repair, Installation, or Maintenance Needs

Changing your furnace filter regularly is a vital part of furnace maintenance, playing a significant role in avoiding unwarranted repairs and extending the lifespan of your HVAC system. At Evergreen Heating & Cooling, we understand the importance of this routine maintenance task and incorporate it seamlessly into our repair and tune-up services.

Should you find yourself in need of furnace repair, replacement, or a comprehensive tune-up, you can count on Evergreen Heating & Cooling to be there for you. As a leading heating and air conditioning specialist in Central Texas, we are fully equipped to address all your HVAC needs. Feel free to reach out to us for top-notch service, and rest assured that your peace of mind is our priority.

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401 S 13th St,
Waco, TX 76706





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