Furnace Filter Direction – Which Way Is the Right Way?

Furnace filter direction

Ensuring your furnace filter is installed correctly is crucial not only for the efficiency and longevity of your HVAC system but also for maintaining optimal indoor air quality. The direction of the filter is a key factor that impacts system performance and air cleanliness, making it a vital piece of knowledge for homeowners.

This topic is more relevant than ever as people increasingly focus on health and energy efficiency in their homes. Understanding the correct furnace filter direction can significantly enhance your living environment and system durability, providing a foundational step toward better home maintenance.

⭐ The Right Way to Install a Furnace Filter

Furnace filter direction

Exact filter locations vary by unit, but you can use the following as a general guide for locating your filter:

  • For horizontal air conditioner units (air flows horizontally through the unit), find the filter on the side of the unit.
  • For vertical upflow units (spent air comes in from the bottom of the unit), find the filter in the bottom door.
  • For vertical downflow units (spent air comes in from the top of the unit), find the filters (these units usually require two filters) in the top door.

If you remember ahead of time, note the furnace filter direction before removing it from the unit. The right direction is necessary to trap airborne particles effectively. Set the old filter aside after removing it and grab your new filter. 

Check along the cardboard edges of the filter for an arrow. The arrow will indicate the air flow direction through your heating and cooling system. The arrow on furnace filters must point toward the furnace system and away from the return duct. The side of your filter showing a wireframe should face outward, away from the unit.

air flow direction shown on air filter
Watch out for the filter direction arrow!

✅ PRO TIP: Do yourself a favor and mark it on the indoor air handling unit!

Take a permanent marker and draw your own airflow direction arrow on the HVAC unit near the furnace filter access door. Draw it in the same direction the arrow on your next filter will face. Doing this will help you remember which direction the filter needs to go when you replace it in a few months.

air-flow-direction-on-an-indoor-air-handler
Make sure the two arrows are going in the same direction!

Which Way Does the Air Filter Go In?

The direction in which you install your air filter matters.

If you install your air or furnace filter opposite of what it should be, your HVAC system will be subject to unnecessary wear. Debris will build up in your filter more quickly, forcing your unit to work harder to heat or cool your home.

Heating and air conditioning are crucial to the comfort of your home. Therefore, by installing your air furnace filters in the wrong direction, you are doing not only your air system a disservice but also negatively impacting the well-being of everyone living under your roof. Correct furnace filter direction keeps HVAC systems running more efficiently and effectively.

Incorrectly Installed Filter

furnace filter installed incorrectly
This filter was incorrectly installed and ended up being sucked into the fan housing.

⭐ How Do I Know When My Filter Needs Replacing?

The furnace filter is often the first step in HVAC troubleshooting. If you notice a decrease in airflow from your returns, your filter may need replacing. Return ducts bring in the air from your home and send it through the filter. Furnace filters trap many airborne particles that impede airflow and impact the quality of your home’s air.

Signs of a clogged air filter include a decrease in energy efficiency, which you will notice on your next utility bill. You may also notice your air conditioning unit shutting down before it reaches the temperature you set on the thermostat, a decrease in the air pressure from the return duct, or cold air blowing when it should be warm and vice versa.

Dirty vs clean air filter
You can tell the difference!

⭐ How Often Should I Change My Filter?

The general rule is that the thicker your air filter, the less often it needs replacing. However, the real answer depends on your home and lifestyle. Most filters need changing every 30 to 90 days. Those with pets at home need to replace their air filter more often than those without pets due to the hair and dander they produce.

Changing your air filters should be part of your home’s routine maintenance program. Proper filter maintenance means you get more life out of your furnace and air conditioner, allowing you to hold off the prospect of installing a new HVAC system in the distant future.

⭐ What Are the Best Filters?

HVAC tech with a pleated air filter

Furnace filter ratings score filters on their ability to capture air particles. This is known as the MERV (Minimum Efficiency Reporting Value) rating system. Filters with higher MERV ratings are best at stopping particles from blowing out into your home.

PRO TIP: Pleated filters are the best for your home. Learn more about indoor air quality and filters right here: Air Filter Guide

To determine the ideal filter for you, find the correct size that you need (this is shown on your current air filter or in your furnace or AC owner’s manual), compare MERV ratings and cost, and consider any special needs of your home.

Do you have pets? Do you struggle with allergies? The best air filters keep your air flowing through the air handler without impediment, blowing the cleanest air out into your home.

⭐ Find the Right Filter For Your Home!

Phyxter Approved Logo on Service Truck

In this guide, we explored the importance of correct furnace filter installation, focusing on the correct direction for optimal performance and air quality. Proper installation ensures efficiency and prolongs the lifespan of HVAC systems, making it a critical consideration for homeowners.

Phyxter Home Services brings expertise and experience, ensuring you receive the most reliable and professional HVAC service. We invite you to discover more through our insightful articles on air quality and filters. Need immediate service? Contact a Phyxter Contractor today for same-day assistance in Vernon, Kelowna, and surrounding areas.

Related Reading: Air Filter Guide. MERV Filter Ratings and What They Mean For Homeowners.

Jake Gibson

Jake Gibson is a force to be reckoned with in the HVAC industry. As the CEO of Phyxter, he has made it his mission to revolutionize how contractors work. With a background in HVAC, entrepreneurship, and technology, Jake brings innovation and expertise to this traditional industry.

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