When is the Right Time to Change Your HVAC Air Filter?

Learn when is best time to change your HVAC air filter based on factors such as system running time & outdoor air quality.

When is the Right Time to Change Your HVAC Air Filter?

The ideal is to change your air filter every three months, however, there are certain factors to consider when determining when to change an old filter. We are going to explore each of these factors in detail. The most important factor is how often the system is running. The filter collects dust and debris only when the system is operating.

The more it works, the faster the filter picks up dirt. During a cold winter, a furnace filter will need to be changed more often than during a mild winter. On the other hand, you will need to change the filter more frequently during a hot and humid summer than during a mild summer. Remember that a filter also gets dirty during AC mode.

Do you find pet hair in your oven filter? Hair fibers from dogs, cats, rabbits and other mammals are large compared to dust and dirt that normally trap the filter. That means they clog the filter and block the airflow pretty quickly. The more important clean air is, the more often the filter needs to be cleaned or changed. A coarse-media filter, MERV 11 or higher, or an electronic air filter is the best option when someone in the household has asthma, severe allergies, or difficulty breathing for any reason.

The air will be cleaner than if a basic fiberglass air filter is used. You may also want to consider an air cleaner for your system. Cheap fiberglass filters require less frequent replacement than pleated filters. Some sites get this exactly the other way around, claiming that thicker filters can last longer between changes.

That goes against the design of the filters. Coarse-media filters trap more and smaller dust particles, so they obviously clog up faster. Slim fiberglass filters don't trap as much dirt and debris, so they don't clog up as quickly. The good news is that some of those filters can be cleaned with a nylon brush and placed back in the oven or air controller instead of replacing them.

Cleaning should be done outside or in a garage to keep dust and dirt out of your home. If removing dirt with a brush instead of replacing the media filter, be sure to change the filter after two or three cleanings. In the end, brush cleaning will not remove enough deeply embedded dirt and debris. In larger homes, more air flows through the filter than in smaller houses.

Because the air carries dust, pet hair, and other debris, the filter will get dirty more quickly in a system that serves a large house. Some of you wonder what we mean by continuous fan mode and why a homeowner would use it. There must be a setting in the thermostat, such as Auto and Fan options. In automatic mode, the fan works only when the system is heating or conditioning the air in your home.

In fan mode it works all the time until you turn it off. The longer the system works, even if it is not heating or air conditioning, the faster the filter will get dirty and it will need to be changed. Is continuous fan mode a good idea? Here are the pros and cons. First, clean air by passing it through an air filter more often means that it will need to be changed more frequently.

Second, it helps balance temperatures in your home. Third, if you have a basement, you can draw cool air from there to help cool upstairs rooms. Running the fan requires electricity so you'll see an increase in your electricity bill. Secondly, basement air is usually more humid than upstairs air which makes you uncomfortable in summer so you'll need to lower thermostat settings to get rid of moisture which causes your AC to work more often resulting in higher electricity costs.

In summary, continuous fan mode is not recommended as a standard operating procedure. So how do you know when it's time to change your air filter? You may hear a little wheezing even when it's clean but it will worsen when it's dirty which indicates that it's blocking airflow to your system which means not enough hot or cold air outlet resulting in hazards that can be easily avoided by checking your filter regularly and changing it when necessary. The only way to ensure how often you need to change your air filter is to perform a visual inspection of it every month after which you'll get an idea of how quickly it gets dirty and re-evaluate if you have a new pet or if outdoor air quality has been poor recently. A general rule of thumb for pleated air filters (such as those manufactured by FilterBuy) is to replace them every 90 days as their efficiency decreases as they trap more dirt, dust and allergens from the air over time.

If you have an electronic media filter however then you don't need to worry about replacing them every 1-3 months but rather wait 6 months to a year before replacing them with an exact model.