Your house leaks air you can't see. A blower door test is a measured diagnostic that puts one honest number, in CFM50 (cubic feet of air leaking through the house each minute at 50 pascals of pressure), on how much air escapes through gaps around windows, rim joists, recessed lights, and attic hatches: a Medford home tested at 4,460 CFM50 against about 2,200 sq ft of conditioned space, an extremely leaky house. Novus Mechanical performs blower door testing across Freehold and Monmouth County, and most tests start at $350.
A blower door is a calibrated fan that mounts in an exterior doorway. We seal the panel into the frame, we run the fan using Retrotec gauges, and we pull air out of the house. As inside pressure drops, outside air rushes in through every gap, and we read the leakage rate in CFM50. Sealing those leaks saves about 15% on heating and cooling, according to ENERGY STAR, so the result is a measurement you can act on, not a guess.
A blower door test reveals how leaky your whole Freehold house is, in one measured number. Most homeowners feel the symptoms before they name the cause. A bedroom over the garage runs cold in January. The bills climb year after year. Leak problems cause as many of those complaints as broken equipment does. First, we measure the total leakage in CFM50 using Retrotec gauges. Second, we rank the gaps from worst to smallest. Air sealing is among the cheapest ways to cut a bill, since sealing the leaks saves about 15%, according to ENERGY STAR, and it usually pays off before new insulation does, the trade-off we cover in air sealing versus insulation. In a humid Climate Zone 4A summer, where Monmouth County design heat hits 91 degrees, a leaky envelope drags in moisture that leaves the house sticky at 72. Most blower door tests start at $350.
A blower door test is a one-hour measurement of a home's air leakage, run start to finish in a single visit. Here is how Novus runs the test in your Freehold or Monmouth County home.
Then you get the report. It is written, it is the same visit, and we walk you through what the numbers mean before we leave. Sealing the leaks the test finds saves about 15% on heating and cooling, according to ENERGY STAR, and most tests start at $350.
The headline result is air changes per hour at 50 pascals, written as ACH50. ACH50 is the number of times per hour the whole house swaps air while the fan holds a set pressure. A lower number means a tighter house. A higher number means more leakage, higher bills, and more comfort complaints. For a sense of where a Freehold home should land, here is what counts as a good blower door score. New homes today are built far tighter than a 1980s home, and the ENERGY STAR program sets tightness targets for new construction. Most existing homes around Freehold sit well above those targets, which is normal and fixable. We measure the house using Retrotec gauges and turn the ACH50 result into a plain list. First, here is your leakage in CFM50. Second, here is where the air moves. Third, here is what to seal first, since sealing saves about 15%, according to ENERGY STAR. Most blower door tests start at $350.
A Freehold homeowner had already given up and expected to replace his AC. Several other companies had come and gone without finding the cause. A blower door test is the tool that changed that. It read around 3,100 CFM50 on a house of about 2,600 sq ft, leaky but nowhere near the worst Novus sees. A Manual J came next and confirmed the existing 3-ton unit was actually the right size. The real problem was a leaky unit cabinet and leaky supply ductwork, not the equipment, so the fix ended up being a like-for-like inverter heat pump plus sealing the leaks. A blower door test does not only catch oversized systems. In a new-construction home in Millburn, a pre-drywall test found a poorly sealed backyard window, several other leak points, and a missing fresh-air intake on two sealed-combustion furnaces, all before the walls closed those mistakes in for good.
Air sealing and radon control are one job in Freehold, because Freehold sits in EPA Radon Zone 1, the highest tier. One local data set averaged about 10.5 pCi/L, well above the 4 pCi/L action level. Most Freehold homes have basements, and a basement is where air sealing and radon meet. Seal a leaky basement the wrong way, and you can change how radon moves through the house. First, we measure the whole envelope using Retrotec gauges. Second, we plan the sealing so radon mitigation still works. The problem is sharpest in the 1960s Stonehurst and Monmouth Heights split-levels off Route 9, where 55 to 60 year old construction leaks through the basement and rim joists. We seal to cut bills by about 15%, according to ENERGY STAR, without pushing soil gas where it does not belong. Most blower door tests start at $350.
Here is the mistake we see all the time. A homeowner replaces an aging AC or furnace, the contractor matches the old unit's size, and the new system is just as oversized as the last one, because nobody measured the house. A leaky home and a tight home need different sized equipment, and improper sizing cuts efficiency by up to 30%, according to ENERGY STAR. First, we measure the envelope in CFM50 using Retrotec gauges. Second, we feed the real leakage number into the Manual J load calculation. That is how we size the replacement right instead of bolting on a unit that short-cycles and leaves you humid. If the test shows heavy duct loss, duct leakage testing and duct sealing come first. Novus technicians hold NCI System Performance (#25-142-01) and Air Balancer (#25-143-01) certifications. Most blower door tests start at $350. The leakage is the second of the Four Numbers Novus checks on every job: the load, the leakage, the static pressure, and the score on the finished system. See how those four fit together on how we work.
We measure your home, explain what we find, and hand you one clear price. Book a consultation in Freehold or Monmouth County.
Updated September 2026 by Novus Mechanical, Freehold, NJ
