What is a Blower Door Test and Why Do You Need One?
The Basics
A blower door test is a diagnostic tool used to measure how airtight a home is. In simple terms, it shows how much air is leaking through gaps and cracks in your home's exterior—things like windows, doors, electrical outlets, and even the smallest holes you can’t see.
Until the last decade or so, air leakage wasn’t considered much of a priority which means that if you live in an older home, not only are you likely dealing with unfiltered air entering your house, but that you’re paying to cool or heat that new air over and over each hour. Most older homes end up with a blower door result of around 5 to 8 air changes per hour, meaning that in the summer time, you’re paying to have your air conditioner cool all new air in your home every 7-1/2 minutes. Most modern homes on the other hand prioritize air sealing to reduce that leakage down to 1-2 air changes per hour, allowing your HVAC equipment to work significantly less, and save you significant amounts on money on your monthly electrical bills.
How It Works
A technician installs a temporary, airtight frame with a powerful fan into an exterior door—this is the blower door. When the fan is turned on, it either pulls air out of the house or pushes it in, creating a pressure difference between the inside and outside. Special gauges then measure how much air flows through the fan to maintain that pressure.
The more air the fan has to move, the leakier the house.
Why It Matters
Improves Energy Efficiency: The less your home leaks, the less your HVAC system has to work.
Boosts Comfort: A tight home means fewer drafts and more consistent indoor temperatures.
Enhances Indoor Air Quality: Airtight homes allow for controlled ventilation, keeping out allergens and pollutants.
Protects the Structure: Reducing air leakage also helps manage moisture, which can prevent mold and rot.
When to Get One
Blower door tests are typically done:
During new construction (often required by code)
As part of a home energy audit
After major air sealing or insulation upgrades
Bottom Line: A blower door test is one of the best ways to understand your home's performance and make informed improvements. It's a small step that can lead to big savings—and a more comfortable, durable home.