By J. David Odom, Richard Scott, AIA, and Norman Nelson, PE

ptac unitIn the mid-1980s the hospitality industry developed some of the earliest niche hotel prototypes catering to the needs of the business traveler (such as Marriott Courtyards). A number of these hotels quickly began to suffer moisture, mold, and odor problems during their first one or two summer seasons. These problems were especially pronounced in the Southeast US. Presently, the hospitality industry is embracing similar minimalist style prototypes aimed at attracting millennials.  Avoiding similar problems from several decades ago are both a competitive business opportunity as well as a risk management opportunity.

Many of these issues centered around the HVAC systems of choice: through-the-wall air-conditioning units (often known as PTAC units) combined with inadequate fresh outside air systems. The manufacturer’s implied promises that the PTAC units could achieve adequate moisture and odor control at low first costs in virtually all climates is not always true.  It became evident in the early 1990’s that certain combinations of wall & HVAC systems had much higher failure rates, especially in warm and humid climates.

Most hotels did not have moisture & mold problems but those that did have problems were sometimes multi-million dollar failures. Several decades ago the authors discovered that low risk, economical hotels could be built by identifying the repetitive causes of moisture and mold problems unique to PTAC hotels.  By slightly modifying the design, construction, and operational choices, the outcomes proved to be much more resilient.  

These opinions are arrived at after having consulted on hotels with a combined total of over 150,000 guest rooms since 1985, including most of the hotels at Walt Disney World. This article will discuss why PTAC-related moisture and mold problems occur in some hotels and not others, plus how to avoid these problems.

Authors Richard Scott and David Odom are with Liberty Building Forensics Group and Norman Nelson is with CH2M.