When I run a blower door test for a homeowner or builder in Nashville, the score you see is more than just a number. It tells us exactly how tight or leaky the home is. ACH50 stands for Air Changes per Hour at 50 Pascals. In simple terms, it measures how many times the air inside your home is replaced by outside air in one hour when the house is pressurized to 50 Pascals. The blower door equipment simulates steady wind pressure, similar to a constant breeze, and records how fast air slips through cracks, leaks, or gaps in the building shell.
A lower ACH50 means the home is sealed better. That translates into less wasted energy, lower utility bills, less strain on the HVAC system, and healthier indoor air since fewer pollutants and moisture are able to sneak inside.
The answer depends on the age and quality of the home. Older houses in Middle Tennessee can easily score between 10 and 20 ACH50, which is why many feel drafty in winter and hot in summer. A new home without dedicated air sealing often falls between 7 and 10 ACH50. Modern energy codes and efficiency programs like ENERGY STAR set much higher standards, and most quality new builds in the Nashville area are aiming for scores between 3 and 5 ACH50. On the cutting edge, Passive House construction achieves about 0.6 ACH50, which is extremely airtight and delivers maximum efficiency.
Your blower door test score directly impacts how your home feels day to day. A tighter home is easier to heat and cool, keeps rooms more comfortable, and prevents moisture issues like mold. Meeting or exceeding lower ACH50 targets also makes it easier to pass code inspections, qualify for rebates or incentives, and can even improve resale value in competitive markets like Franklin, Brentwood, and the greater Nashville area.
The good news is that if your score comes back higher than you’d like, there are clear steps to improve it. Sealing gaps around windows and doors, adding insulation, and sealing ductwork are all proven ways to reduce leakage. Even small upgrades can make a noticeable difference in comfort and efficiency, while lowering your ACH50 into a much healthier range.