Blower door testing in Cedar Rapids & Eastern Iowa
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. The same leaks work against you in summer, carrying humid outdoor air in — see indoor humidity levels for Iowa homes.
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.
How to get your house ready for a blower door test
You don’t have to do much. We turn off the furnace, water heater, exhaust fans, and dryer ourselves and put everything back the way we found it. A few things on your end help the test go smoothly.
- No fire in the fireplace or wood stove. Make sure the ashes are cold. The test pulls outside air in through the chimney and can blow ash into the room.
- Close the windows and exterior doors. We’ll check them before we start, but it saves time.
- Don’t seal anything up just for the test. No tape over outlets or plastic on windows the day before. We want the number for the house the way you live in it.
- Clear a path to the front door, the attic access, the basement, and the furnace and water heater.
- Plan for pets. The fan is loud and fills the front doorway for a good part of the visit. A quiet room or a crate works best.
- Tell us about vermiculite or old asbestos materials. If your attic has loose, pebbly vermiculite insulation, or you know of damaged asbestos materials in the house, mention it when you book. BPI standards don’t allow a depressurization test where asbestos could get into the air, so we plan around it.
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. Plan on mechanical ventilation — the building code requires whole-house ventilation in any home that tests below 5.0 ACH50.
Code-compliant
Code-compliant new construction. The 4.0 ACH50 target is the current Iowa new-construction ceiling — and because it’s under 5.0, the home also needs whole-house ventilation.
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.
Iowa’s blower door rules for new homes
Iowa uses the 2012 IECC as its statewide energy code for homes three stories or fewer, with its own amendments. Every new home has to pass a blower door test, and the details trip people up more often than the number does.
4.0 ACH50 or lower
Iowa set its own air leakage limit at 4.0 air changes per hour at 50 Pascals, and it covers the whole state. The model 2012 code calls for 3.0 in our climate zones; Iowa amended it to 4.0.
How the house must be set up
- Windows, exterior doors, and fireplace doors closed, but not sealed beyond their normal weatherstripping
- Exhaust, intake, makeup air, and flue dampers closed, not taped
- Interior doors open
- Continuous ventilation and HRV openings closed and sealed
- Heating and cooling off, supply and return registers fully open
Any time after the last penetration
The code allows the test once every penetration through the thermal envelope is in place — plumbing, wiring, ducts, flues, and light fixtures. Testing goes best when no other trades are working in the house.
A signed written report
Whoever runs the test signs a written report of the result for the code official. Where the code official requires it, the test has to be done by an approved third party. We don’t sell insulation or air sealing, so the number is a straight answer.
Passing means you need ventilation
The building code (IRC Section R303.4) requires whole-house mechanical ventilation in any home that tests below 5.0 ACH50. Since Iowa caps new homes at 4.0, every new home that passes needs a ventilation system. Plan for it from the start, not after the test.
Find it, fix it, retest
A failed test isn’t the end of the job. With the house still under pressure, we walk it with a thermal camera and smoke to find the biggest leaks, so your crew knows exactly what to seal before the retest.
What a blower door test costs in Eastern Iowa
It depends on what the test is for. Here’s how pricing works with us. If the test is part of a DOE Home Energy Score or another rating, it’s included in that service’s price.
Included in a $699 audit
Our home energy audit is a flat $699 for any size home. It includes the blower door test, infrared imaging of every wall and ceiling, and a written plan ranked by payback. If you want to know why your house is drafty or expensive to heat, it’s usually a better value than a test alone.
What a home energy audit costs →$550 REScheck + blower door
For new construction, our REScheck package covers the certificate for your permit and the blower door test (duct testing extra if needed). Need testing only, or several homes? Ask for a quote.
Request a builder quote →Quoted by size and location
Need just the number, for a pre-purchase check or to verify air sealing? Standalone pricing depends on the size of the home and how far we drive. Send the address and a little about the house, and we’ll get back to you with a price.
Request a quote online →Blower door test or full energy audit?
You need a number
Choose a standalone test when the question is “how tight is it?”
- Energy code compliance on a new home
- Checking an air sealing or insulation contractor’s work
- Before you buy a house
About two hours. You get CFM50, ACH50, and the biggest leaks we find with the house under pressure.
You need answers
Choose an audit when the question is “why?” Why the bedroom over the garage is cold, why the furnace never seems to shut off, why the windows sweat in winter, and what to fix first.
The audit includes the same blower door test plus infrared imaging and a written plan ranked by payback. Plan on 2 to 3 hours on site.
Request your audit →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 DOE Home Energy Score Assessor, and HERS ratings are available on request — so your results can be documented for 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, and North Liberty, along with the smaller communities in between. Not sure whether your address is in range? Send it through our contact form 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?
What is a good blower door test number?
How do I prepare for a blower door test?
Can I do a blower door test myself?
Does every new home in Iowa need a blower door test?
Can a house be too tight?
Does air leakage affect summer humidity?
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? Send us a quick note online and we’ll help you pick.