Furnace Filter Maintenance: A Homeowner’s Guide

HVAC technician doing maintenance on a furnace and replacing the filter.

Replacing your furnace filters regularly is essential to maintain indoor air quality and keep your heating system running efficiently. This article provides a handy guide to everything homeowners need to know about furnace filter care and replacement.

Why Change Furnace Filters?

Furnace filters trap dust, pollen, pet dander and other particles to improve air quality. But over time filters get dirty and clogged, causing:

  • Reduced airflow and strain on your HVAC system
  • Spikes in energy bills from working harder
  • Buildup of dust and allergens in the home
  • Foul odors circulating from the furnace

Replacing clogged filters restores proper airflow and efficiency. As a rule of thumb, aim to change furnace filters every 3 months.

dirty discolored air filter needing replacement.

Dirty, discolored furnace filter in need of replacement

Locating Your Furnace Filter

Furnace filters are typically found in one of these locations:

  • Return air ducts – Check for a vent or grille on the wall, ceiling or floor. The filter will be behind it.
  • Furnace cabinet – Open the panel to locate the filter slot inside the furnace itself.
  • Air handler unit – Check inside the closet or cabinet holding your furnace/AC system.

air filter located in the furnace.

Common places to find your furnace air filter

Before accessing the filter, always turn off your furnace’s power for safety.

Determining Furnace Filter Size

Furnace filters come in standard sizing like 20x30x1, 16x25x4. To find your size:

  • Look at the existing filter for its size.
  • Otherwise, measure and note the length, width and depth.
  • Round up to the nearest standard size.
  • Consider the thickness – 1″, 2″, 4″ etc.

Also check your furnace manual or ask an HVAC pro for the right size.

Installing the New Filter

When inserting the new filter:

  • Look for airflow direction arrows on the filter. Arrows should point toward furnace.
  • Slide filter into slot securely with no gaps.
  • Double check the filter sits flush within the slot.

This ensures optimal filtration. Replace the furnace panel once done.

Filter Types and MERV Ratings

Aim for a filter with a higher MERV rating for better air filtration.

filter types and merv rating

Higher MERV ratings trap more particles

However, a filter too dense for your system can restrict airflow. Consult your furnace manual or an HVAC pro on ideal filter types and MERV ratings.

When to Call a Professional

While regular filter changes are doable yourself, call an HVAC technician if:

  • You’re unable to locate the filter.
  • The filter is stuck in place and won’t budge.
  • Issues like reduced airflow or high energy bills persist after replacing filter.
  • You have questions about filter sizing, type or MERV ratings.

Routine furnace filter replacement is simple and critical for indoor air quality and system performance. Follow this guide to make the task quick and eas