Looking for a blower door tester in O'Fallon, IL? Describe your project once and up to three certified energy testers who work in O'Fallon and St. Clair County get back to you with a quote. It's free and there is no obligation.
O'Fallon is home to about 32,169 people (2024 Census Bureau estimate), a stable community (−0.8% since 2020). With 2,035 people per sq mi, it is a suburban area. New homes and additions here go through energy code inspections that often include air leakage testing.
O'Fallon at a glance
- Population (Census Bureau estimate, 2024)
- 32,169 (−0.8% since 2020)
- Rank in Illinois
- 59th of 1,294 cities and towns
- Land area
- 16 sq mi
- Population density
- 2,035 people per sq mi (suburban)
- Type
- City (O'Fallon city)
- Main county
- St. Clair County
What to check before hiring in O'Fallon
- Code: in Illinois, the energy code adopted by the state or city sets the limits and the tests.
- Timing: schedule a pre-drywall test to catch leaks early.
- Report: make sure the report format matches what the inspector expects.
- Price drivers: number of homes, tests and trips.
Useful official resources
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Building Energy Codes Program (DOE)
Official information and guidance.
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RESNET
Official information and guidance.
Services available in O'Fallon
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Blower door test
Air leakage test of the building envelope, with the report required for code compliance.
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Duct leakage test
Duct leakage test of the HVAC system as required by the energy code.
Frequently asked questions in O'Fallon
How much does a blower door test cost in O'Fallon, IL?
It depends on the number of homes and tests. Describe your project: testers who serve O'Fallon reply with a quote.
How long does it take?
About an hour per test for a typical home.
Can I test existing homes?
Yes, it is part of most energy audits.
Which certified energy testers will contact me?
Up to three independent certified energy testers who serve O'Fallon and the surrounding area, chosen for the service you need. Your details are shared only with your consent.
Source: U.S. Census Bureau, Population Estimates Program (Vintage 2024) and Gazetteer Files (public domain), imported on 10/31/2026. Figures describe the incorporated place or county as published; they are shown for information only.