What You'll Learn

• How to run a duct leakage test in measureQuick using the Quick Tests menu
• What duct leakage testing measures and why it matters for system performance
• The difference between total leakage and leakage to outside
• Equipment setup: connecting a DG-1000 or similar duct tester
• Step-by-step procedure from register sealing through pressurization to CFM results
• Pass/fail thresholds based on ACCA Standard 5 and ASHRAE 62.2
• How results attach to the project and generate reports

What You'll Need

• Device: iPhone (iOS 15+) or Android phone (Android 10+) with measureQuick installed
• Account: measureQuick account with NCI Air Upgrade (see NCI Air Upgrade Setup)
• Duct tester: DG-1000 pressure/flow meter from The Energy Conservatory, or equivalent duct testing device
• Sealing materials: Register covers, tape, or magnetic covers to seal all supply and return registers
• Tubing: Flexible tubing for pressure connections
• Time: 20-30 minutes depending on system size and number of registers

What Duct Leakage Testing Measures

Duct leakage testing quantifies the amount of conditioned air lost through duct joints, connections, seams, and penetrations before it reaches the living space. Even a well-installed duct system loses some air. The question is how much.

Leaky ducts waste energy, reduce delivered airflow, create pressure imbalances in the building, and make it harder for the HVAC system to maintain comfort. A system that delivers 350 CFM per ton at the equipment but only 280 CFM per ton at the registers is fighting its own distribution system.

There are two test methods:

Total Leakage

Measures all air escaping from the duct system, including leaks into conditioned spaces (inside the building envelope) and into unconditioned spaces (attic, crawlspace, garage). This test is simpler to run because you do not need to isolate the duct system from the building.

Leakage to Outside

Measures only the air escaping into unconditioned spaces. This is the more consequential number because air leaking into unconditioned spaces is truly lost - it does not contribute to heating or cooling the occupied space. Running this test requires simultaneously pressurizing the building envelope (using a blower door) to neutralize the pressure difference between conditioned and unconditioned spaces, then measuring duct leakage under that condition.

For most field service scenarios, total leakage is the standard test. Leakage to outside is typically required for code compliance testing on new construction or major renovations.

Step-by-Step Guide

Step 1: Open the Quick Test

From the measureQuick home screen, open an existing project or create a new one. Navigate to the Quick Tests menu. Select Duct Leakage.

measureQuick opens the duct leakage test interface, which walks you through the setup and measurement process.

measureQuick Quick Tests menu showing Duct Leakage Screening and other test options

Step 2: Seal All Registers

Before pressurizing the duct system, seal every supply and return register in the building. Use register covers, painter's tape, or magnetic covers designed for this purpose. Every open register is a leak path during the test, and unsealed registers will make the measured leakage far higher than actual duct leakage.

Check all rooms, including closets and utility spaces. Missed registers are the most common source of inflated leakage readings.

[Visual Reference] A supply register in a ceiling or wall covered by a magnetic register cover, creating an airtight seal for duct leakage testing. The magnetic cover sits flat over the register grille, blocking all airflow through that opening. Every supply and return register in the building must be sealed this way before pressurizing the duct system.

Step 3: Connect the Duct Tester

Attach your DG-1000 (or equivalent duct tester) to the duct system. The standard connection point is a return grille opening - remove the grille and attach the duct tester's fan and flow ring to the opening using the provided adapter panel.

Connect the pressure tubing:

• Channel A measures the pressure inside the duct system relative to the room (duct pressure reference)
• Channel B measures the flow through the duct tester fan

Ensure all connections are airtight. A loose connection at the duct tester introduces error into the measurement.

Step 4: Pair the Duct Tester with measureQuick

If your DG-1000 supports Bluetooth or Wi-Fi data transfer, pair it with measureQuick so readings stream directly into the app. If your device does not support wireless transfer, you will enter the readings manually after the test.

For NCI Air integration setup details, see NCI Air Upgrade Setup.

Step 5: Pressurize the Duct System

Turn off the HVAC system. With the duct tester fan running, pressurize the sealed duct system to 25 Pascals (the standard test pressure for residential duct leakage). The DG-1000 adjusts fan speed to reach and hold this target pressure.

Once the duct system stabilizes at 25 Pa, the duct tester measures the airflow required to maintain that pressure. That airflow, in CFM, equals the total duct leakage at 25 Pa (CFM25).

Wait for the reading to stabilize. Fluctuations of more than 5-10 CFM indicate a leak in the test setup (loose register cover, incomplete seal at the duct tester connection) or wind effects on the building.

Step 6: Record the Results

measureQuick captures the CFM25 reading. If your duct tester is paired wirelessly, the value populates automatically. If not, enter the CFM25 value manually.

The app calculates leakage as a percentage of total system airflow:

Duct Leakage % = CFM25 / Total System CFM x 100

If you have already measured total system airflow (from a TrueFlow test, flow hood measurement, or the equipment's rated CFM), measureQuick uses that value. If not, it uses the equipment's nominal airflow based on tonnage (400 CFM per ton as a default).

Pass/Fail Criteria

measureQuick evaluates duct leakage against established industry thresholds:

For a 3-ton system with 1200 CFM nominal airflow:

• 4% threshold = 48 CFM25 maximum (new construction)
• 6% threshold = 72 CFM25 (good condition for existing)
• 8% threshold = 96 CFM25 (acceptable for existing)

A reading above 8% on an existing system indicates significant duct leakage worth addressing. A reading above 4% on new construction fails the ACCA Standard 5 requirement.

How Results Attach to the Project

The duct leakage test saves to the current project alongside any other quick tests or diagnostic workflows you have run. The results appear in:

• The project's test history
• Generated PDF reports (free with Quick Tests)
• The measureQuick dashboard for that project

If you run a duct leakage test before and after duct sealing work, both results are stored in the project. This creates a documented before-and-after comparison for the customer.

Video Walkthrough

• YouTube (measureQuick): (3,389 views, 39 min). Includes discussion of airflow testing workflows that connect to duct leakage evaluation

Tips & Common Issues

My leakage reading is extremely high (over 200 CFM25 on a small system)

Check for unsealed registers first. A single open register can account for 50-100+ CFM of apparent leakage. Walk through every room and verify every register is covered. Also check that the air handler cabinet door is fully closed and sealed.

The pressure will not reach 25 Pa even at maximum fan speed

The duct system has very large leaks - possibly disconnected duct sections, open boot connections, or a return plenum that is not sealed. This is actually a useful finding: the system has severe duct integrity problems. Document the condition, note the maximum pressure achieved and the CFM at that pressure, and report to the customer.

Should I test with the filter in or out?

Test with the filter removed. The filter is not part of the duct system's air barrier, and leaving it in place restricts airflow through the duct tester without changing the leakage measurement. Removing it makes the test easier to run and does not affect results.

When should I run a leakage-to-outside test instead of total leakage?

Leakage to outside is typically required for energy code compliance on new construction or major renovations. It requires a blower door running simultaneously, which adds equipment and time. For routine service and maintenance, total leakage is the standard test.

The customer wants to seal their ducts - how much improvement is realistic?

Professional duct sealing (mastic, aerosol-based sealing, or mechanical fastening and sealing of connections) typically reduces leakage by 30-60% depending on the starting condition. Re-test after sealing to document the improvement.

Related Articles

Prerequisites (complete these first):

• Total External Static Pressure - Understanding TESP and why airflow measurements matter
• Static Pressure Screening - Quick static pressure check before deeper duct evaluation

Follow-up articles (next steps after this one):

• NCI AirMaxx Test - Room-by-room airflow distribution testing
• Component Pressure Drops - Evaluating individual duct section contributions to pressure loss

Related in the same domain:

• BluVac Evacuation Test - Another quick test for vacuum and decay testing
• NCI Air Upgrade Setup - Setting up the NCI Air integration required for duct testing in measureQuick

Need Help?

If you get stuck or this article does not answer your question:

• Check the Related Articles section above
• Contact measureQuick support: support@measurequick.com
• Schedule a training session with the measureQuick training team