Your house feels drafty by the baseboards in January and clammy by August, and you want to know where the air is actually getting in, not just how much. A blower door test answers both questions in one visit: a whole-house leakage number, and a room-by-room map of where that air is moving. Novus Mechanical runs these tests across Freehold and Monmouth County, and the number matters less than what we find while we're chasing it.
Local housing stock leaks in predictable places, and most of them trace back to how these homes were actually built, not bad luck or poor upkeep. A blower door test from Novus starts at $350 and includes a written report the same visit.
The calibrated fan drops the house to 50 pascals of pressure and outside air comes rushing in through every gap at once, which is what makes the leaks findable instead of theoretical. In this housing stock, five spots do most of the damage: the attic hatch or pull-down stairs, recessed lighting cans, the rim joist where the foundation meets the framing, chases cut for ductwork running between floors, and the wall shared with an attached garage. A 1970s split level adds a sixth: knee walls.
None of these are exotic. They're just places where the original builder cut a hole for something else, wiring, plumbing, a duct, a set of stairs, and never circled back to seal around it. ENERGY STAR flags these same kinds of spots, attic hatches, recessed lighting, and duct chases among them, as the first places to check in any home, which lines up with what we find on a typical Monmouth County house.
A knee wall is the short stud wall that separates a finished room from the unconditioned attic pocket behind a sloped roofline, and split levels around Freehold and Howell are full of them. Behind that wall is often bare framing with little or no air barrier, sitting directly against outside temperature. It looks like a finished wall from the bedroom side and acts like an open window from the attic side.
We find this constantly on split levels with an added bonus room over the garage. The room never quite holds temperature, and the owner assumes the furnace is undersized. Usually the knee wall behind the closet is the actual problem, not the equipment.
An attached garage shares a wall, sometimes a ceiling, with living space, and the door between them is rarely sealed as tightly as an exterior door needs to be. Beyond comfort, that shared boundary is a safety line: a leaky garage wall can pull car exhaust and stored chemical fumes into the house, not just cold air. We check the door threshold, the penetrations where wiring and plumbing cross that wall, and the firewall condition while we're in there, because that boundary is doing two jobs at once.
The blower door gives a number. Thermal imaging shows the leak. While the house is depressurized, a thermal camera picks up the temperature difference where outside air is actively pulling through a gap, and that image is worth more to a homeowner than any CFM50 figure. You can see the cold line tracking down from a recessed light or along a rim joist, instead of taking our word for where the problem is.
We pair thermal imaging with the blower door specifically because the two together turn a leak into something you can point at. That combination is also what separates a real diagnostic from someone eyeballing your attic with a flashlight and guessing.
The number tells you how leaky the house is overall. It does not tell you where to spend the first dollar. Two houses can post the identical ACH50 and need completely different repairs, one dominated by a single bad rim joist and the other spread thin across a dozen small penetrations. A ranked list of specific leaks is what actually gets acted on. A number by itself usually just gets filed away.
| Where the leak is | Why it happens in this housing stock | Roughly how hard to fix |
|---|---|---|
| Attic hatch or pull-down stairs | Cuts straight through the air barrier, rarely gasketed on original construction | Easy: weatherstrip and an insulated cover |
| Recessed lighting cans | Original cans in 1960s to 1980s ceilings were not built airtight | Moderate: seal or box each can from the attic side |
| Rim joist | The band where the foundation meets the framing sits exposed in most basements | Moderate: foam board and sealant around the full perimeter |
| Ductwork chases between floors | Cut for a supply or return feeding an upper floor or split level, rarely sealed at the penetration | Moderate to hard, depending on wall access |
| Attached garage wall | Shares a boundary with living space, plus the door threshold and old penetrations | Moderate, and it's a safety fix as much as an energy one |
| Knee walls, split levels | Bare framing behind a finished wall, sitting against an unconditioned attic pocket | Hard: usually needs a rebuilt air barrier behind the wall |
We run blower door testing across Freehold, Marlboro, Manalapan, Colts Neck, Holmdel, Howell, and the surrounding parts of Monmouth County. Residential homes only. If the ducts running through your attic or crawlspace look suspect, we'll flag it for a duct leakage test too, since that's a separate leak path from the shell. For the scoring side of your report, see what a good blower door score actually looks like by house era, and if you're planning sealing and insulation together, read which one goes first.
Technicians are on site Monday through Friday, 8 AM to 6 PM, and the phone is answered any time so you can get on the schedule. A blower door test starts at $350 and includes the written, ranked report the same visit.
Five spots account for most of the leakage in this housing stock: the attic hatch or pull-down stairs, recessed lighting cans, the rim joist, chases cut for ductwork between floors, and the wall shared with an attached garage. Split levels around Freehold and Howell add knee walls as a sixth common source. Each of these traces back to a hole the original builder cut and never sealed around, not to poor maintenance.
On new construction, the house does not get its certificate of occupancy until it passes, so the builder seals further and retests. That is the whole reason to test before the walls close up rather than after. On an existing home there is nothing to fail: the test produces a number and a list of leaks, and what you do with it is your call. Nobody is going to red-tag a house for being leaky.
We measure your home, explain what we find, and hand you one clear price. Book a consultation in Freehold or Monmouth County.
Updated August 2026 by Novus Mechanical, Freehold, NJ
