Air Leakage Diagnostic Testing

Recently, QED Lab was asked to perform diagnostic testing on a PTAC system installed within a building mock-up to evaluate potential air leakage concerns. PTAC systems, or Packaged Terminal Air Conditioners, are self-contained heating and cooling units commonly found in hotels, condominiums, medical facilities, dormitories, and apartment communities. These systems are designed to pass directly through exterior walls, with vents and heat exchange components located on both the interior and exterior sides of the building envelope.

Because PTAC systems penetrate the building enclosure, they can become a significant source of uncontrolled air leakage if not properly designed, installed, or sealed. In modern construction, especially on projects targeting improved energy efficiency, reduced air leakage, or energy certification programs, these penetrations are often areas of concern. Even small gaps around louvers, sleeves, or interfaces can allow unwanted air movement that impacts building performance.

During this project, QED technicians performed diagnostic testing using party fog as a visual investigative tool. Fog testing is commonly used during building enclosure diagnostics because it allows technicians to visibly track air movement through assemblies and interfaces. When fog is introduced near suspected leakage areas, any air intrusion or exfiltration becomes immediately visible, helping identify deficiencies that may otherwise go unnoticed during standard inspections.

While testing the PTAC mock-up, technicians observed fog intruding through the louver interface of the unit. This observation indicated areas where air was bypassing the intended air barrier and moving through unsealed or insufficiently sealed pathways. Leakage at the louver interface can create several issues for buildings, including increased energy loss, reduced occupant comfort, moisture intrusion potential, and pressure imbalance throughout the structure.

In buildings designed to meet stricter air leakage requirements, PTAC penetrations can become especially problematic if overlooked during construction. Many modern projects pursue energy credits, enhanced commissioning requirements, or compliance with advanced energy codes that emphasize continuous air barrier performance. Excessive leakage around PTAC systems may negatively impact whole-building airtightness testing results and make it more difficult for projects to meet their performance targets.

Air leakage associated with PTAC systems can also contribute to condensation issues and moisture migration within wall assemblies. When warm, humid air infiltrates cooler building cavities, condensation may develop over time, potentially affecting insulation performance, indoor air quality, and long-term durability of building materials. Identifying these pathways early during mock-up testing allows project teams to make corrections before widespread installation occurs across the building.

Mock-up testing plays an important role in identifying enclosure deficiencies before construction is completed. By evaluating assemblies in controlled conditions, project teams can verify installation quality, observe real-world performance, and improve details before they are replicated throughout the project. Diagnostic tools such as fog testing provide immediate visual confirmation of leakage locations and help contractors better understand how air is moving through the system.

QED frequently performs diagnostic and performance testing related to building enclosure systems, including air leakage investigations, water penetration testing, and whole-building airtightness evaluations. Early identification of PTAC leakage issues can help reduce long-term operational costs, improve occupant comfort, and support overall building performance goals.