(Hidden) AC Filter, that almost NOBODY knows about !!
/Many homeowners in the Houston area diligently change their main HVAC (or AC) filter every 1–3 months, but a surprising number overlook one critical component: the often-hidden, rinsable filter in the fresh air intake unit, typically located in the attic.
At ATEX Inspects (www.atexinspects.com), we frequently spot this during our thorough Residential Inspections across Greater Houston, and we want to help you avoid the pitfalls of neglecting it.
Why Changing (or Cleaning) Your HVAC Filters Matters
Your AC system's primary air filter traps dust, pollen, pet dander, mold spores, and other airborne particles before they circulate through your home or reach the equipment. When it's clean:
Indoor air quality improves — Cleaner air reduces allergens and respiratory irritants, which is especially important in humid Texas climates where mold can thrive.
Energy efficiency increases — A clogged filter restricts airflow, forcing your system to work harder and consume more electricity. Regular maintenance can lower your utility bills noticeably.
System longevity extends — Reduced strain prevents premature wear on components like the blower motor and coils, potentially avoiding expensive repairs or early replacement.
Consistent comfort is maintained — Better airflow means even cooling throughout your home without hot spots or reduced performance.
Experts generally recommend checking or replacing the main filter every 1–3 months, depending on usage, pets, and dust levels—more often during our intense Houston summers. Some of the newer HVAC systems have media filters (large around 4 inches thick) at the return plenum in the attic. These generally last 6 months - to a year.
Don't Forget the Hidden Fresh Air Intake Filter
Many modern HVAC systems include a fresh air intake to bring in outside air for better ventilation (especially in tightly sealed homes). This duct often runs from the roof or exterior to the return plenum in the attic and includes a secondary filter—frequently a reusable, rinsable one (sometimes foam or mesh-type).
This filter is easy to miss because:
It's tucked away in the attic.
It may look like a simple screen or box rather than a traditional pleated filter.
Homeowners rarely know it exists until an inspection or service call points it out.
Builder’s fail to mention it’s existence in newer builds.
Access requires tools
If neglected, this filter becomes degraded & clogged with leaves, insects, pollen, and heavy dust from outside air. The consequences include:
Reduced fresh air flow, leading to poorer indoor air quality and stuffiness.
Extra strain on the main system as it compensates.
Potential for debris to bypass and contaminate the entire HVAC setup.
The good news? Many of these intake filters are designed to be rinsed with water, dried, and reinstalled—making maintenance quick and cost-free (Occasionally needing replacement). Check yours every 3–6 months, or more frequently if your home is near trees, construction, or high-pollen areas.
Simple Maintenance Tips
Locate your main return filter (often in a hallway grille or near the air handler).
Schedule attic access to inspect the fresh air intake unit—look for a duct with a filter box or grille.
Rinse reusable filters gently and let them air dry completely before reinstalling.
If you're unsure or uncomfortable accessing the attic, call a professional.
Regular filter care is one of the easiest ways to protect your family's health, save money, and extend your HVAC system's life—especially here in hot, humid Houston.
At ATEX Inspects, our detailed inspections catch these often-overlooked details so you can address them early. Whether you're buying, selling, or maintaining your home, we're here to help.
Visit www.atexinspects.com to schedule your inspection today and breathe easier knowing your system is in top shape! (281) 216-1112