Blower Door & Duct Leakage Testing

Measure Where Your Home and Ductwork Are Losing Air

Advanced Service Company LLC provides calibrated duct and building-envelope tightness testing for new construction, existing homes, builders and qualifying light-commercial properties throughout North Alabama.

Request Tightness Testing Call 256-432-7622

Testing requirements and pass/fail thresholds vary by adopted code, project type and local jurisdiction.

Duct and building envelope tightness testing in North Alabama
Since 2008Local Experience
Calibrated TestingMeasured Results
HVAC #09005Alabama Certified
TVA QCN MemberTrusted. Qualified. Local.
Testing Services

Blower Door, Duct Leakage and Air-Leakage Diagnostics

Choose the testing scope that fits your construction project, comfort concern, sealing work or documentation requirement.

Blower Door Testing

A calibrated fan temporarily installed in an exterior doorway measures whole-building air leakage at a standardized pressure.

Duct Leakage Testing

A calibrated duct-testing fan measures leakage from the supply and return duct system at a standardized test pressure.

New-Construction Verification

Testing can help builders, contractors and homeowners document performance for applicable plans, programs or local requirements.

Existing-Home Diagnostics

Testing can help locate excessive leakage that may contribute to discomfort, humidity, dust or high energy use.

Pre- and Post-Sealing Testing

Before-and-after measurements can document changes after approved air-sealing or duct-sealing work.

Air-Leakage Investigation

Diagnostic testing can be paired with visual inspection or pressure diagnostics to identify likely leakage pathways.

HVAC Airflow Evaluation

Testing results can support a broader review of duct design, return-air pathways and comfort complaints.

Energy-Efficiency Consultation

Results are explained in practical terms with prioritized recommendations based on the property.

Building Envelope

What Is a Blower Door Test?

A calibrated fan is installed in an exterior doorway and used to create a controlled pressure difference across the building envelope. The airflow required to maintain that pressure indicates the building's total measured leakage.

Results may be reported as CFM50 or converted to ACH50 using the building volume.

HVAC Ductwork

What Is a Duct Leakage Test?

Registers are temporarily sealed and a calibrated fan is connected to the duct system. The tester measures the airflow required to hold the system at a standardized pressure, commonly reported as CFM25.

The exact test method and interpretation depend on project stage, duct location and applicable requirements.

Do You Need Testing?

Common Reasons to Schedule Tightness Testing

High Energy Use

Unexpectedly high heating or cooling use may be related to air leakage, duct leakage, equipment condition or building-envelope performance.

Hot or Cold Rooms

Room-to-room temperature differences can be affected by duct leakage, pressure imbalances, insulation or airflow problems.

Drafts Near Doors or Windows

Noticeable drafts can indicate uncontrolled air leakage through the building envelope.

Dust from Attics or Crawlspaces

Leaky return ducts and envelope openings can draw unconditioned air and particles into the home.

Humidity Problems

Air leakage can bring humid outdoor air into wall cavities, crawlspaces and conditioned areas.

Long HVAC Run Times

Excessive leakage can increase the heating and cooling load and make equipment operate longer.

New Construction or Addition

Testing can help verify workmanship and identify leakage before finishes make repairs more difficult.

Planned Air or Duct Sealing

A baseline test helps prioritize work and provides a measurable point of comparison.

Understand the Measurements

ACH50, CFM50 and CFM25 Explained

ACH50

Air changes per hour at 50 pascals. This normalizes blower-door leakage based on the building volume.

CFM50

Cubic feet per minute of airflow required to maintain 50 pascals during a blower-door test.

CFM25

Cubic feet per minute measured at 25 pascals, commonly used for duct leakage reporting.

Code reminder: Verify the adopted code, amendments, permit documents and enforcing jurisdiction before applying a test threshold.
Potential Benefits

Why Measure Leakage Before Choosing Improvements?

Measured Results

Testing provides numerical results instead of relying only on visual inspection.

Better Comfort

Reducing uncontrolled leakage may help improve room-to-room temperature consistency.

Improved Humidity Control

A tighter envelope and sealed ducts can reduce humid-air infiltration when ventilation is properly addressed.

Cleaner Indoor Environment

Sealing leaks may reduce dust, insulation fibers and outdoor pollutants entering through uncontrolled pathways.

HVAC Performance Support

Lower leakage can reduce unnecessary load and help conditioned air reach intended rooms.

Prioritized Improvements

Testing helps identify whether envelope leakage, duct leakage or another issue deserves attention first.

Verification After Work

Post-sealing tests can document whether approved improvements changed measured leakage.

Code and Program Support

Testing can provide documentation for applicable local code, builder or efficiency-program requirements.

Our Testing Process

From Project Review to Measured Results

1

Project Review

We discuss the building, test purpose, construction stage, HVAC system and any applicable documentation requirements.

2

Building Preparation

Exterior openings, combustion appliances, interior doors and HVAC controls are prepared according to the selected test procedure.

3

Blower Door Setup

A calibrated fan and pressure gauge are installed in an exterior doorway for envelope testing.

4

Duct Tester Setup

Registers are temporarily sealed and calibrated equipment is connected to the duct system when duct testing is requested.

5

Pressure Testing

The building or duct system is brought to the required standardized test pressure and airflow is measured.

6

Diagnostic Investigation

When included, pressure diagnostics and visual inspection are used to identify likely leakage areas.

7

Results & Recommendations

We explain the measurements, limitations and practical next steps.

8

Post-Improvement Verification

A follow-up test may be performed after approved sealing work to document the new result.

Loose vs. Improved

What Excessive Air Leakage Can Affect

Excessive or Uncontrolled Leakage

  • Drafts and comfort complaints
  • Longer HVAC run times
  • Dust and attic or crawlspace air entry
  • Humidity and pressure imbalances
  • Conditioned-air loss through ducts
  • Hard-to-prioritize improvement work

Measured and Properly Addressed

  • Targeted sealing recommendations
  • Documented baseline and post-work results
  • Improved comfort potential
  • Reduced uncontrolled infiltration
  • Better duct-delivery potential
  • Ventilation considered as part of the plan
Code & Program Testing

Testing Requirements Depend on the Project and Jurisdiction

Energy-code adoption, amendments and enforcement vary. New-construction builders should confirm the required test type, construction stage, reporting format and threshold with the local building official before scheduling.

For TVA EnergyRight projects, eligibility, rebates and required procedures depend on the participating local power company and current program rules.

Before You Schedule

Have the permit or program requirements available so the correct test and documentation can be planned.

Discuss Your Project
New Construction

Testing for Builders, Contractors and New Homeowners

Schedule testing at the correct construction stage to document performance and identify leakage while repairs may still be accessible.

  • New homes and additions
  • Rough-in or final duct testing
  • Final blower door testing
  • Documentation for applicable requirements
Request New-Construction Testing
Existing Properties

Diagnostics for Comfort and Efficiency Concerns

Testing can help identify whether whole-building or duct leakage deserves attention before spending money on repairs or upgrades.

  • Drafts and uneven temperatures
  • Dust and humidity complaints
  • Pre-sealing diagnostics
  • Post-sealing verification
Request Existing-Home Testing
Related Services

Turn Test Results into Practical Improvements

Duct Sealing

Seal accessible duct leaks identified through inspection and testing.

Learn more →

Load Calculations

Measure heating and cooling requirements for system selection.

Learn more →

HVAC Installation

Install properly selected equipment after building and load evaluation.

Learn more →

Indoor Air Quality

Coordinate filtration, humidity and ventilation with tighter construction.

Learn more →

Duct Cleaning

Remove accessible debris from qualifying duct systems.

Learn more →

HVAC Maintenance

Maintain airflow, filters, coils, drains and system performance.

Learn more →

Duct and Envelope Tightness Testing Across North Alabama

Contact us to confirm service availability, project-stage requirements and testing documentation.

Somerville, ALDecatur, ALHuntsville, ALMadison, ALAthens, ALHartselle, ALPriceville, ALTrinity, ALTanner, ALHarvest, ALHazel Green, ALEva, AL
Testing FAQ

Blower Door, Duct Leakage and Code Questions

The visible questions below match the FAQPage schema included with this page.

It is diagnostic testing that measures air leakage through a building envelope and HVAC duct system using calibrated fans and pressure gauges.

A blower door test uses a calibrated fan mounted in an exterior doorway to pressurize or depressurize a building and measure whole-building air leakage.

Duct leakage testing uses a calibrated fan to pressurize or depressurize the duct system and measure air escaping through leaks.

ACH50 means air changes per hour measured with the building at a pressure difference of 50 pascals. It normalizes blower-door airflow to the building volume.

CFM50 is the airflow in cubic feet per minute needed to maintain a 50-pascal pressure difference during a blower door test.

CFM25 is airflow measured at a 25-pascal pressure difference, commonly used when reporting duct leakage.

A standardized pressure creates repeatable conditions so leakage can be measured and compared.

It measures total leakage and can help locate major pathways, but concealed construction and access limitations may prevent every leak from being identified.

Testing itself does not reduce energy use. It helps identify leakage so appropriate improvements can be prioritized. Actual savings vary.

Testing can identify leakage that may contribute to drafts, uneven temperatures, humidity problems and long HVAC run times.

A tighter home may require planned ventilation and combustion-safety consideration. Air sealing should be coordinated with ventilation and appliance requirements.

Requirements depend on the adopted code, project type and local enforcing jurisdiction. Confirm requirements with the local building official before construction or testing.

Requirements depend on the adopted energy code, duct location, construction stage and local jurisdiction. The building official determines what is required for a specific project.

Alabama code adoption and local enforcement can change. Builders and owners should verify the applicable residential or commercial energy code with the local authority having jurisdiction.

Yes. We provide qualifying blower door and duct leakage testing for new homes, additions and selected light-commercial projects.

Yes. Existing-home testing can help investigate comfort, dust, humidity and energy-efficiency concerns.

Scheduling depends on the test and project stage. Duct tests may occur during rough-in or after completion, while final blower door testing is usually performed when the envelope can be properly prepared.

Exterior doors, windows, attic access panels, mechanical penetrations and other envelope components generally need to be installed or prepared according to the test protocol.

Yes. The applicable procedure and interpretation depend on duct location, project requirements and the requested test.

Yes. Registers and grilles are temporarily sealed so calibrated equipment can measure duct-system leakage.

The test uses temporary equipment and pressure differences designed for diagnostic testing. Fragile areas or unsafe conditions should be disclosed before testing.

Time varies with building size, number of duct systems, preparation, access, required documentation and whether diagnostic leak investigation is included.

Yes. Available documentation may include test conditions, measured results and general recommendations. Specific reporting requirements should be discussed before scheduling.

We offer qualifying duct sealing, air sealing, HVAC and related services. Repairs are quoted separately from diagnostic testing.

Post-improvement testing is the best way to document the measured change after approved sealing work.

Yes. Return-side leaks can pull air and particles from attics, crawlspaces, garages or wall cavities, while supply leaks can create pressure imbalances.

Air leakage can transport humid air into building assemblies and conditioned spaces. Moisture sources and ventilation should be evaluated together.

Advanced Service Company LLC is a TVA EnergyRight Quality Contractor Network member. Program eligibility, rebates and required procedures depend on the participating local power company and current program rules.

We serve qualifying properties in Somerville, Decatur, Huntsville, Madison, Athens, Hartselle, Priceville and surrounding North Alabama communities.

Call or text 256-432-7622, or use the online booking link to request duct or envelope tightness testing.

Stop Guessing Where Your Home or Ductwork Is Losing Air

Request calibrated duct and building-envelope tightness testing for your North Alabama project.

Request TestingCall 256-432-7622

Regular hours: Monday–Friday, 7:00 AM–5:00 PM