Blower door testing
Certified, calibrated blower door testing for homeowners, builders, and real estate professionals across Eastern Iowa. Home Star Iowa is a BPI Testing Center based in Cedar Rapids — we test for new-construction code compliance, HERS ratings, pre-purchase inspections, and the comfort problems that make a house feel drafty, cold, or expensive to heat.
What a blower door test measures
A blower door is a calibrated fan that temporarily replaces one of your exterior doors. We seal the fan into the opening, turn it on, and pull air out of the house until the inside is at a 50-Pascal pressure difference from the outside. At that point, every gap, crack, and unsealed penetration in the building envelope is trying to pull outside air in. The fan measures how much air has to move to hold that pressure difference — and that number tells us how leaky the house is.
CFM50
Cubic Feet per Minute at 50 Pascals. The raw airflow through the fan — a direct measure of how much air the house is leaking.
ACH50
Air Changes per Hour at 50 Pascals. CFM50 normalized to the size of your house — how many times the entire volume of air inside the home would be replaced in one hour at test pressure. ACH50 is the number most codes, programs, and energy raters use.
When you need a blower door test
There are four common reasons homeowners and builders in Eastern Iowa call us for a blower door test.
Code compliance
The Iowa energy code requires a blower door test on every new home, with a maximum leakage of 4.0 ACH50. For a builder, it’s the final check before the certificate of occupancy. For a homeowner, it’s independent verification the envelope was built tight, not just drawn tight. Need the permit paperwork too? We also prepare REScheck reports for Iowa building permits.
New construction services →Before you buy
A standard inspection tells you the furnace is 12 years old. It won’t tell you the house leaks like a sieve. A test before closing gives you a real number for what you’re buying — and a preview of the winter gas bill. For older homes around Cedar Rapids and Iowa City, often the most useful pre-purchase test a buyer can order.
Verify the work
Just had air sealing, insulation, or a major renovation done? The only way to know it worked is to measure. A before-and-after test quantifies the improvement as a number — and it’s required for most utility rebate programs and any project needing an updated HERS rating.
Comfort problems
Cold bedroom over the garage. Drafty floors. A furnace that runs constantly. These are almost always air leakage problems, and a blower door is the single best tool for finding them. Paired with infrared imaging during the test, we point directly at the band joists, recessed lights, attic hatches, and duct chases driving the problem.
What happens during the test
A standalone blower door test typically takes about two hours. Here is what the appointment looks like.
Setup and walkthrough — 20–30 min
We review the house with you, identify the conditioned volume (basements and conditioned crawlspaces count as inside the envelope), close all exterior windows and doors, open all interior doors, and check combustion appliances. Exhaust fans, dryers, and HVAC get turned off or covered so they don’t influence the test.
Fan installation — 10 min
The blower door assembly goes into an exterior door opening — usually the front door. An adjustable frame seals the opening, and the calibrated fan mounts into the panel.
The test — 10 min
We depressurize the house to 50 Pascals and record the airflow, typically taking multiple readings and sometimes running the fan at lower pressures to generate a full leakage curve.
Leak identification — 30–45 min
While the house is under pressure, leaks are easy to find. We walk through with a smoke pencil, a thermal camera, or the back of a hand to identify the biggest leakage points. This is the part that actually tells you what to do next.
Breakdown and report — 15 min
The fan comes out, the house goes back to normal, and we review results with you on the spot. A written report follows.
What the results mean
Once we have your ACH50 number, here is roughly how to read it in an Iowa climate.
Tight
ENERGY STAR territory and the target for high-performance new construction. Mechanical ventilation is required at this tightness to maintain indoor air quality.
Code-compliant
Code-compliant new construction. The 4.0 ACH50 target is the current Iowa new-construction ceiling.
Well-built
Typical of well-built homes from the last 20 years, or older homes that have been air sealed.
Average existing home
Typical of an average existing home in Eastern Iowa. Usually a strong candidate for air sealing.
Leaky
Often an older home with no air sealing done — and the house that will see the biggest improvement from a weatherization project.
What a test costs
If your blower door test is part of a larger service — a DOE Home Energy Score, a RESNET HERS rating, or a BPI energy audit — the blower door is almost always included in the price of that service rather than billed separately. A full home energy audit is a flat $699 for any size home — see what a home energy audit costs in Iowa. Standalone test pricing depends on home size and location; call 319.244.8564 for a quote.
Numbers only as good as the equipment
Calibrated Retrotec systems
Blower door numbers are only as good as the equipment and the protocol. We run calibrated Retrotec systems — the industry-standard manufacturer — and maintain them on the manufacturer’s recalibration schedule.
BPI Testing Center
Testing follows BPI (Building Performance Institute) protocols. Owner Rob Novak has been a BPI Certified Building Analyst and Trainer since 2009. We’re also a RESNET HERS Rater and DOE Home Energy Score Assessor — a combination that means your results are accepted by code officials, utility rebate programs, real estate professionals, and ENERGY STAR.
Serving Cedar Rapids and Eastern Iowa
We provide blower door testing throughout Eastern Iowa, including Cedar Rapids, Marion, Hiawatha, Iowa City, Coralville, North Liberty, Waterloo, and Cedar Falls, along with the smaller communities in between. Not sure whether your address is in range? Call or email and ask — we’re usually able to accommodate.
A few things people ask
How long does a blower door test take?
What does ACH50 mean?
What is the blower door target for new construction in Iowa?
How much does a blower door test cost?
Do I need to be home during the test?
Can a blower door test damage my house?
Ready to get a number on your house?
Independent blower door testing across Cedar Rapids and Eastern Iowa. Not sure whether a standalone test or a full audit is the right fit? Call and ask — we’ll walk you through the options.