Why You Should Always Change Your Air Filters Before the Arrival of Spring

Change your air filter before spring because a winter-clogged filter restricts airflow just as pollen season and the first cooling days arrive. A clean filter protects the blower and coil, keeps the air cleaner, and helps your system run efficiently. The U.S. Department of Energy recommends checking filters monthly and replacing them at least every three months.

In northern Delaware the timing is practical. Heating season leaves a heavy load of dust, pet hair and fabric lint in the filter, and pollen season starts soon after. A fresh filter in March or early April gets the whole system ready before you ask it to cool the house.

What a dirty filter does to your system

An HVAC filter exists to protect equipment, and cleaning your air is the secondary job. As it loads with debris, airflow through the system drops. The Department of Energy states that a clean filter in place of a clogged one can lower air conditioner energy use, and that restricted airflow forces the system to work harder than it was designed to.

The consequences we see in homes include:

• A frozen evaporator coil, because too little warm air crosses it.
• Overheating and shutdown on a furnace that cannot move enough air.
• A strained blower motor, which is an expensive part to replace.
• Dust buildup on the coil and inside ducts that no one wants to clean out.
• Rooms that never feel comfortable, especially upstairs.

Why spring is the right moment

Winter dirt is still in there

Houses are sealed up from November on, so what comes inside stays inside. Pet dander, skin cells, cooking particles and fibers from carpet gather in the filter all winter. If you changed the filter in December and forgot, you are likely running on a spent filter now.

Pollen arrives early

Trees in our area begin releasing pollen in early spring, followed by grasses. When you open the house on the first warm days or when the air conditioner starts cycling, that pollen reaches your filter. Starting with a new filter gives it room to work.

Cooling season is hard on weak airflow

Mixed-humid climate zone 4A means long stretches of hot, damp weather. An air conditioner needs good airflow across its coil to remove humidity. Poor airflow cuts that capacity right when you need it.

How to pick the right filter

Filters carry a MERV rating from 1 to 20 that describes how well they trap particles. Higher ratings catch smaller particles, but they also resist airflow. The EPA notes that a higher-rated filter can improve indoor air, as long as your system can handle the added resistance. Many residential systems do well with a mid-range filter. Very dense filters in a system that was not designed for them can starve it of air.

• Check the size. The dimensions are printed on the filter frame. Nominal size and actual size differ slightly, so match the frame’s printed number.
• Check the airflow arrow. It should point toward the blower, not toward the return grille.
• Match the filter to the household. Pets, allergy sufferers and smokers may want a higher rating, within what the system allows.
• Avoid cheap, thin fiberglass unless that is all your system is built for. It protects the equipment but captures little.
• Ask us if you are unsure. We can tell you what your system tolerates.

Where the filter lives

Finding the filter is half the battle. The common locations are:

• In a slot beside the furnace or air handler in the basement, closet or attic.
• Behind a large return grille on a wall or ceiling.
• In a media cabinet attached to the furnace, which holds a thicker filter that is changed less often.

Many older homes in Wilmington and Newark have more than one return, so check every grille. Write the replacement date on the frame with a marker so you remember.

A before-spring filter checklist

• Turn the system off at the thermostat before pulling the filter.
• Remove the old filter and note its size and the direction of the arrow.
• Check the color. A gray, matted surface means it is spent.
• Wipe visible dust from the filter slot and the area around the return.
• Insert the new filter with the arrow pointing toward the blower.
• Vacuum the supply and return grilles.
• Check that no vents are blocked by furniture.
• Write the date on the filter and set a phone reminder.
• Look at the condensate drain pan and line if you can see them. Standing water is a problem.
• Clear the outdoor unit of leaves and debris before it starts for the season.

How often to change it afterward

The Department of Energy suggests checking monthly and changing at least every three months. In practice, the interval depends on your house. Homes with pets, heavy carpet, construction or smokers need more frequent changes. Homes with a thick pleated media filter may go longer. During pollen season and during extended heating or cooling stretches, check monthly. What the filter looks like is more reliable than the calendar.

What a filter will not do

Filters catch particles. They do not remove odors, gases or humidity. If your home has persistent allergy complaints, stale air or humidity problems, the answer may be more than a filter. Our indoor air quality page covers the options beyond a filter. The EPA also reminds homeowners that source control and ventilation matter at least as much as filtration.

Special cases in Delaware homes

• Heat pumps and mini splits. Because they run in every season, they collect dust more steadily than a furnace and air conditioner pair. Ductless indoor units have washable filters that need a rinse every few weeks during heavy use.
• Homes with new construction or remodeling nearby. Drywall dust clogs filters quickly, so check weekly until the work ends.
• Homes with a boiler and window air conditioners. Without a ducted system there may be no filter at all, so clean the window units’ screens each spring.
• Rental or vacation properties. A filter that sat for a season still needs replacing, and a fresh one belongs in place before a new occupant arrives.

Common mistakes we see

The mistakes are usually small. A filter is installed backward. The wrong size is wedged in and bypasses air around the edges. A second filter is stacked on top of the first, which doubles the restriction. The filter slot cover is left off, so unfiltered air gets pulled straight into the blower. Or the filter is changed faithfully every year but the return grilles in the bedrooms stay covered with dust. Each one reduces airflow or lets dirt reach the coil, and each is easy to fix once you know to look.

Pair the filter change with a tune-up

Filter changes are a homeowner’s job, but a spring check goes further than we can see from the filter slot. A technician measures airflow, tests capacitors, cleans coils, checks refrigerant and clears the drain. Our AC maintenance visits catch problems before the first heat wave, and the Comfort Club plan puts those visits on a schedule so you do not have to remember.

When to call a pro

Call us if you replaced the filter and airflow is still weak, if the coil or refrigerant line is icing, if you smell something musty when the system starts, or if the system short cycles. These are signs of a problem beyond the filter. Our AC repair team will diagnose it. Bernard M. wrote that we “Arrived on time, with a text letting us know the exact time. Very polite and honest.”

Want a spring check before the heat arrives? Call True Blue Heating & Air at (302) 729-8783 to book your visit.