You spent a year making decisions. Flooring samples. Cabinet pulls. Paint colors debated in four different lighting conditions. You watched every detail go into that house.

What you probably didn't watch was what went into the ductwork.

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The expectation

New means clean. That's the assumption baked into buying a new home versus an old one. Old homes have decades of dust, pet dander, whatever the previous family's habits left behind. New homes are different. They start fresh.

Except for the ducts.

What the construction timeline actually looks like inside your HVAC

Here's a phase-by-phase picture of what's entering your duct system during a typical new construction build:

Framing: Wood dust. Sawdust from cuts. It settles everywhere, including any duct openings that are already roughed in.

Rough-in HVAC: The duct system goes in. Openings are — in most cases — left open. This is standard practice.

Insulation: Fiberglass or mineral wool fibers become airborne during installation and find their way into every open space, including duct boots and register holes.

Drywall: The highest-volume contamination event of a residential build. Drywall sanding generates silica dust fine enough to stay airborne for extended periods. Every open vent acts as a collection point.

Paint: VOC-carrying particles and micro-droplets. Overspray. All of it moves through the air while the HVAC system continues to run.

Flooring and trim: Additional dust, adhesive vapors, and fine particles from cuts. By this point, the system has been accumulating debris for months.

Punch list and cleanup: A shop vac gets run through the visible surfaces. The ducts are not typically part of this cleaning — they're sealed behind registers now, out of sight.

The myth: "My builder will clean the ducts before we move in."

Ask your builder this directly. The answer, more often than not, will be a variation of: "we do a walkthrough cleaning," or "the HVAC gets tested at the end," or simply "yes, of course."

What that almost never means is a certified NADCA duct cleaning. A NADCA-compliant post-construction cleaning involves negative-pressure equipment, systematic cleaning of every duct segment, and documentation. It's a real service that costs $450–$1,000 for a residential home.¹

It's rarely included in the standard contract. It's rarely done.

And even when it is done, it addresses bulk debris — the visible material, the larger particles. The fine silica dust, chemical residues from adhesives and sealants, and VOCs from building materials that have settled into the duct system: those don't come out with mechanical cleaning. Research on IAQ in newly built homes has found that unregulated chemical compounds can comprise the majority of total VOC concentrations.²

What debris does over time

Organic material in ducts — wood dust, drywall compound, paint particulates — combined with the seasonal moisture that condenses in ductwork creates conditions that mold requires. Not guaranteed. Not immediate. But the conditions are there. Studies on HVAC dust have found that duct systems can harbor fungal spores with potential respiratory effects on occupants.³

Research tracking indoor air quality in new homes found that formaldehyde and VOC levels from building materials can remain elevated and take years to fully off-gas.⁴ Most homeowners notice signs sometime in the first few years: dark staining at the register edges (often dismissed as dust), musty smells when the system first kicks on for the season, unexplained respiratory symptoms in an otherwise healthy household.

"Had jobs where people react to drywall dust two or three years after building a house," we heard from an indoor air quality inspector with 26 years in residential inspections. "Sometimes you feel it immediately. Sometimes it takes a while."

Read our full interview with an air quality specialist →

What the signs look like (before you should have to look)

If your home is already built, here's what to pay attention to:

• Dark residue at register edges. Not just dust — a gray or black rim around the register frame on the wall or floor.
• Smell when the system first runs. A musty or chemical smell at system startup, especially after the system has been off for weeks or months.
• Respiratory symptoms concentrated at home. Symptoms that are better when you're traveling and worse when you return.
• Dusty surfaces shortly after cleaning. If surfaces are getting dusty unusually fast, particulates may be recirculating from the duct system.

What to do if your home is already built

If construction is complete, the options are:

1. Schedule a professional IAQ inspection. A certified building biologist can test air quality and identify specific contaminants. Worth doing 30–60 days after move-in.

2. Schedule a NADCA-certified duct cleaning. Not a standard HVAC maintenance cleaning — specifically a post-construction protocol. Costs $450–$1,000 and removes the bulk of the debris.¹

3. Upgrade filtration. Higher-efficiency filters at the air handler, regularly changed, reduce ongoing recirculation of particles. They don't fix the duct liner but they interrupt the cycle.

What to do if you're still in the build

If construction is ongoing, this is the easiest problem to solve. A temporary vent cover — installed at rough-in, removed at trim-out — keeps debris out of the duct system from day one.

It costs a fraction of a post-construction cleaning. It takes 30–60 minutes at rough-in. And it's the difference between a duct system that starts clean and one that needs remediation.

See how it works →

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The most important thing to understand: a brand-new home is not a clean home until someone makes it one. That conversation is easier to have before the walls close than after.

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Sources

Footnotes

1. NADCA (National Air Duct Cleaners Association) — Cost and Time Estimates: https://www.breathingclean.com/cost-time-estimates. Typical residential duct cleaning: $450–$1,000. ↩ ↩²

2. Nakai et al., "Indoor air quality of newly built houses" — PMC6862697: https://pmc.ncbi.nlm.nih.gov/articles/PMC6862697/. Unregulated chemical compounds comprised approximately 82% of total VOC concentrations in newly built homes. ↩

3. Holopainen et al., "Fungal contamination in HVAC systems" — PubMed PMID 27924457: https://pubmed.ncbi.nlm.nih.gov/27924457/. HVAC dust can harbor fungal spores with potential respiratory health effects on building occupants. ↩

4. Sakai et al., "Variations of formaldehyde and VOC levels during 3 years in new and older homes" — PubMed PMID 16507040: https://pubmed.ncbi.nlm.nih.gov/16507040/. VOC levels in new homes decrease markedly after one year; formaldehyde from wood materials requires a longer off-gassing period. ↩