Case Study: Duct Leakage Test Failure Due to Improper Sealing
Duct leakage testing is a standard requirement for both residential and commercial construction projects in Clark County, and it plays a critical role in building performance and energy compliance. Despite its routine nature, we continue to see projects fail due to avoidable mistakes—most commonly, poorly sealed duct connections.
A recent inspection at a mid-sized commercial building in Clark County illustrates this issue. The HVAC system was fully installed, and the project was ready for final inspection. However, during the duct leakage test, results showed significantly higher leakage than code allows. Upon closer inspection, the problem was immediately clear: several duct connections, elbows, and seams had either incomplete mastic coverage or none at all.
This scenario is all too familiar. Mastic is one of the most effective materials for sealing ductwork, but only when applied correctly. In this case, it was spot-applied or completely missed in critical areas—particularly around joints and hard-to-reach elbows. As a result, the system had multiple leak points that compromised the overall integrity and efficiency of the ductwork.
Failing a duct leakage test at this stage of construction can mean costly delays. Crews had to return, re-seal the ductwork, and schedule a re-test. Not only did this add labor costs, but it also pushed back the project timeline. For general contractors managing tight schedules and budgets, this kind of setback is avoidable with more thorough installation oversight and early-stage quality control.
This case underscores a key takeaway for contractors working on new or existing buildings in Clark County: duct sealing is not a checkbox item. Proper application of mastic—particularly at connections, seams, and elbows—is essential to passing your duct leakage test on the first try. It’s also crucial for long-term HVAC efficiency and occupant comfort.
At our inspection firm, we encourage contractors to schedule pre-test walkthroughs if there’s any uncertainty. Identifying sealing issues early can save time, money, and frustration. Our team has the experience to help spot potential problem areas before they become test failures.
If you're managing a residential or commercial project in Clark County, and you want to ensure your ductwork passes inspection the first time, give us a call. We're here to support your team from installation to final testing.
