HVAC and Vents After Construction

Here is the complaint we hear most often about new houses: it was cleaned thoroughly, it looked perfect, and a week later every surface has a grey film again.

The house is not re-dirtying itself. The HVAC system is doing it.

What is actually in there

Ductwork gets installed early, usually before drywall. Then the drywall goes up and gets sanded, and the trim gets cut, and the tile gets cut, and all of that happens in a building with open duct boots and, frequently, an air handler that somebody ran to take the edge off a July afternoon.

By the time the house is finished, the system holds:

• Gypsum dust from sanding, fine enough to pass through a standard filter
• Sawdust from trim and cabinet work
• Silica dust from tile and masonry cutting
• Insulation fibres and general site debris in the boots
• A filter that is loaded, if there is a filter at all

Then the system runs, and every one of those particles gets a second chance to land on your countertops.

Why order of operations decides the outcome

Drywall dust is gypsum ground to a few microns. Particles that small stay airborne for hours and re-suspend with any air movement. Air movement is exactly what an HVAC system produces.

So the sequence is:

Off during the clean. Turn the system off before the crew starts and leave it off. Cleaning with the air handler running means the crew is competing with a machine that is redistributing dust behind them.

Filters replaced after, not before. A new filter fitted before the clean is a loaded filter by the end of it. Replace it when the wet work is finished.

Registers and returns removed and washed. Not wiped in place. Supply registers unscrew, go in a sink or a tub, and get washed and dried. The return grille is the dirtiest single component in the house and it is usually the one that gets a quick pass with a cloth.

Vacuum inside the boot as far as the hose reaches. With a vacuum that has real filtration — see below. This is not duct cleaning, and nobody should call it that. It removes the debris sitting in the first foot or two, which is where most of the visible material is.

Then run the system, then do a second pass on horizontal surfaces a few days later. The first run after a clean will move some dust. That is what the touch-up pass is for.

The shop-vac problem

A shop vac with a paper bag and a cartridge filter is designed for wood chips and water, not for gypsum at a few microns. Fine dust passes straight through the media and out the exhaust port, which points into the room at floor level and moves a lot of air.

Net effect: you pick dust up off the floor and blow it back into the room, where it settles again overnight. People then conclude the cleaners missed it.

Vacuuming construction dust needs sealed filtration rated for fine particulate. It is the single piece of equipment that separates post-construction work from house cleaning, and it is also why we vacuum before any wet work rather than after.

What cleaning is and is not

Register and grille cleaning is cleaning work. It is in a post-construction final clean.

Duct cleaning — running mechanical brushes and negative-air equipment through the full run of the system — is a separate licensed trade with its own equipment. Any cleaning company that tells you a vacuum hose down a supply boot equals a duct clean is describing something they did not do.

If a new build has visible debris deep in the trunk line, or the ducts were left open through drywall sanding, get an HVAC contractor. That is not an upsell we can make and it is not one we do.

The Whisper Valley wrinkle

Some high-efficiency builds in Manor, including a lot of the Whisper Valley stock, have an energy recovery ventilator. An ERV deliberately pulls outdoor air into the house through its own filtered path, which is how a very airtight house stays breathable.

That path has its own filters, they are not in the same place as the furnace filter, and plenty of owners do not know the equipment exists. At handover they are frequently loaded with construction dust.

If you are taking delivery of an airtight new build anywhere in the metro, ask the builder two questions: where is every filter, and what size. There are often three or four, not one.

A short checklist for handover week

1. System off before cleaning starts
2. All registers and return grilles removed, washed, dried, refitted
3. Boots vacuumed with sealed filtration at the openings
4. Every filter located and replaced, including ERV or fresh-air filters
5. System run for a day
6. Touch-up pass on horizontal surfaces two to three days later

Cost context

Vents, returns and fixtures are inside a standard post-construction final clean, which prices on floor area — roughly $725 for a 2,500 sq ft new build, from $365 on small jobs. Filters and any duct work are separate, and they should be, because they are somebody else’s trade.

The filter is the cheapest item on this list and the one that changes the most. If you do nothing else after a build, replace it, then replace it again a month later.