A lot of homes in Katy — especially ones built from the 1980s through the early 2000s — don’t have metal ductwork at all. They have rigid fiberglass duct board: insulation board formed into rectangular trunks and plenums, with the fiberglass surface exposed on the inside of the airstream. It’s quiet, it insulates well, and when it gets dirty it’s a completely different animal to clean than sheet metal.
We recently finished a duct board job here in the Katy area, and the photos on this page are straight from that project. The before shots show what years of dust, debris, and surface contamination look like on fiberglass board. The after shots show the same duct interiors cleaned and sealed with a white antimicrobial coating. That white finish isn’t paint for looks — it’s Foster 40-20, and it’s the reason this page exists.
Duct board interior after cleaning and Foster 40-20 application — the sealed white surface is the finished coating.
Why Duct Board Can’t Be Cleaned Like Metal Duct
Sheet metal duct can take aggressive brushing. Fiberglass duct board can’t. Hit it with the wrong equipment and you tear the surface, release fibers into the airstream, and shorten the life of the whole system. That’s why some companies simply refuse duct board jobs — or worse, run their standard metal-duct process through it and leave damage behind.
Cleaning duct board properly means soft-bristle agitation matched to the fiberglass surface (never steel whips or hard brushes), HEPA-filtered negative air pulling debris toward the collection unit the entire time, careful access work with openings cut and resealed correctly, and an honest inspection of the surface condition before and after — because board that’s badly degraded sometimes needs repair rather than cleaning.
Before: years of accumulated contamination on the duct board surface.
What Foster 40-20 Is and Why We Use It
Foster 40-20 is an EPA-registered fungicidal protective coating made specifically for HVAC systems — including fiberglass duct board and duct liner. After the air duct cleaning is finished, we apply it as a coating across the interior surfaces of the board. It does three jobs at once.
First, it locks down the fiberglass surface. Older board that’s been in service for decades can get friable — the surface starts shedding. The coating encapsulates it and gives the airstream a smooth, sealed surface instead of raw fiberglass. Second, it inhibits mold and microbial growth. Katy humidity is relentless, and fiberglass board holds onto moisture more than metal does. The fungicidal coating keeps mold and bacteria from re-establishing on the treated surface. Third, it makes future maintenance easier — a sealed surface collects less debris and releases it more easily on the next cleaning.
A full trunk run after coating — sealed from end to end.
Before and After: The Same Ducts
Before: dark speckling across the board surface.
After: the same style of duct board, cleaned and sealed.
Signs Your Duct Board System Needs Attention
A musty or “old house” smell when the AC starts up. Visible dark speckling or discoloration when you shine a light past the vent. Dust returning quickly on furniture near supply registers. Allergy symptoms that ease up when you leave the house. Or simply a system that’s 15+ years old and has never had the ducts serviced.
If you pull a register off and see gray or black speckling on a fuzzy fiberglass surface — that’s exactly the condition shown in the before photos on this page, and it’s worth having looked at.
What buildup looks like from the register opening.
Our Duct Board Cleaning Process
We start with an inspection — confirming the system is duct board, assessing surface condition, and giving you a straight answer on whether cleaning and coating makes sense or the board is too far gone. Then containment and HEPA-filtered negative air run the whole time while we work through the system with soft-bristle tools designed for fiberglass, section by section. Once the ducts are clean, we apply Foster 40-20 evenly across the interior board surfaces, reseal all access points properly, and walk the results with you at the end.
Most single-family jobs in Katy take half a day. Larger two-system homes in neighborhoods like Cinco Ranch or Nottingham Country can run longer — we’ll tell you up front.
Serving Katy and Surrounding Neighborhoods
We handle duct board cleaning throughout Katy, including Cinco Ranch, Seven Meadows, Kelliwood, Grand Lakes, Nottingham Country, Falcon Ranch, Firethorne, and Cross Creek Ranch. If your home is in the 77449, 77450, 77494, or 77441 zip codes, you’re squarely in our service area.
Call (281) 318-5155 for a free assessment — we’ll tell you honestly whether your duct board needs cleaning, coating, repair, or nothing at all.