It is usually advisable to trust the airflow labels on these pre-installed filters as HVAC professionals are well-practiced at understanding how furnaces work. Usually, a furnace will come with a filter pre-installed.
The build-up of dirt is one clue, as are marks that are labeled to indicate the way that air flows. Often, you can determine the airflow on your furnace through simple visual inspection. How Do I Know Which Way the Airflow is on my Furnace? If both sides are dirty again, it is time to call an HVAC technician to do a little maintenance. Then once your furnace has run for a couple of weeks, you should find that only one side is dirty. If you find a filter that is dirty on both sides, first replace or clean it (depending on the type of filter).
Other times, it is possible that the filter was flipped around purposely by someone else. This is usually the case when a furnace filter has become so dirty that the dirt has sucked over to both sides. Sometimes, furnace filters may appear dirty on both the leeward and windward sides. We answer this question in the next subsection.
#Furnace airflow direction how to
This, however, begs the question of how to tell which way the airflow is on your furnace. Given the importance of furnace filters and especially clean furnace filters, it becomes clear why understanding furnace filter dirtiness is important.Īs mentioned above, it is most common to see furnace filters gather dirt, hair, and dust on the side of the filter that first encounters airflow. Which Side Of Furnace Filter Should Be Dirty? Furnaces, especially central furnaces, pull and push air from the entire home, making them especially useful for cleaning all your home's air.Īs demonstrated here, furnace filters not only help keep you and your family healthy, but they also save you money by keeping your furnace running more efficiently and effectively. This extra work leads to higher energy bills and less efficient home heating.įurther, and according to this article from the Environmental Protection Agency, in-home air filtration is one of the best ways to help ensure clean indoor air. Essentially, all the moving parts and heat exchangers in your furnace work less well and age quicker if covered in airborne dirt.Īlso, dirty filters force the furnace fan to work harder to pull the same amount of air. The advice and facts contained in this post are applicable to furnaces with one, two, or even more filters.Īccording to, clean air filters help to keep furnace systems running efficiently by preventing grime and dirt from building up in the system. Some furnaces even have two or more filters to either cover more area or to remove even more dust, dirt, and particulate from the air. Heaters that do not use air filters include electric wall inserts and most plug-in electrically powered heaters. These filters help keep the furnace clean, improve furnace efficiency, and help with indoor air quality.įurnace types with air filters include all central furnaces, mini-split ductless heat pumps, and some plug-in electric heaters. To conclude, we answer several questions related to the topic of this post.Īlmost all home heaters which rely on airflow have cleanable filters built-in or are equipped for disposable filters. Keep reading the rest of this post for more details on why furnaces have filters, which side of the furnace filter should be dirty, and how often to change your furnace filter. If your air filters are dirty in some other fashion, it is likely your furnace is not working properly, or the filter was installed incorrectly. In all cases, the furnace filter should be dirty on the side that the air comes into the furnace from.
#Furnace airflow direction professional
Because of this, you are wondering, which side of the furnace filter should be dirty? We combine industry professional knowledge and up-to-date research to thoroughly answer your question in this post.
Disclosure: We may get commissions for purchases made through links in this post.Īlmost all types of furnaces, no matter their fuel or location, are equipped with air filters.