A Pre-renovation Peer Review Could Have Prevented a Hotel’s Mold Problem

A Simple Band-Aid ‘Fix’

A recent painting project had sealed the outdoor air vents to the vertical air conditioners, causing toilet-exhaust-induced air infiltration to enter the room and wall cavity directly and wash behind the newly installed vinyl wallcovering.
A recent painting project had sealed the outdoor air vents to the vertical air conditioners, causing toilet-exhaust-induced air infiltration to enter the room and wall cavity directly and wash behind the newly installed vinyl wallcovering.

The project team was under pressure to quickly solve the problem so that it would not progress when the construction team moved to the next floor, thereby increasing costs for the client because of unanticipated remediation efforts and extended room outages. Liberty Building Forensics Group began its investigation by looking at the HVAC system. By examining the vertical air-conditioning (VTAC) units in each of the guestrooms, the forensics specialists were able to trace the duct to the outdoor air intake but then couldn’t find where the outdoor air was brought into each of the guestrooms from the exterior.

A conversation with the owner and general contractor revealed that the exterior of the building had been given a paint job by the previous owner prior to the hotel sale. In doing so, the painting contractor had painted over the old louvered screens. Although this action had been requested by the previous owner to make the building look more appealing, the screens were in fact how the outdoor air was introduced into each of the guestrooms. The paint had sealed the screens shut and altered the amount of outdoor air coming in, thus causing the vents to no longer meet the design requirements for the VTAC units. This design change was causing the now-oversized units to short cycle, dropping the temperature very quickly without adequately dehumidifying the rooms.

The general contractor, wall-prep contractor and vinyl contractor had carried out their usual processes of skimming the wall, allowing three days to dry, then continuing with the vinyl wallcovering installation. Because of the increased humidity, however, the skim coat did not dry within the manufacturer’s normal recommended dry time. The typical three days recommended by the manufacturer was under the assumption the hotel was operating at 50 percent humidity and 75 F. Instead, the hotel was now operating closer to 70 percent humidity and 75 F, making three days of dry time insufficient. As a result, the moisture from the undried skim coat was closed in by the new vinyl wallcovering, creating an environment that was very conducive for mold growth.

Peeling Off the Band-Aid

Supplemental dehumidifiers were deployed to allow the construction team to continue with their three-day planned work schedule. Meanwhile, the forensics team conducted further evaluations to determine whether the blocked vents were the only issue causing the mold problem, which was confirmed. The previous owner’s decision to paint the screens rather than replace them had led to a mold problem that could have been catastrophic for this new owner if the mold had not been detected early on in the renovation process.

The options for long-term solutions provided were quite simple: introduce new equipment to pressurize the corridor to provide the proper dehumidification or return to the original building design by fixing the vents. The new owner opted for the easier and less expensive option of fixing the exterior vents and restoring the building back to its original design.

Although this hotel’s mold problem had been caused by a simple mistake, it had evolved into a complex issue through a series of events. Fortunately, the forensics team was able to get involved as soon as the mold made its appearance and addressed the issue before it got out of control. This kept the renovation project moving forward on schedule and prevented any future mold outbreaks.

Hotel owners or general contractors can spare themselves the panic and additional expense of hiring a forensics consulting firm by conducting a peer review prior to starting their renovation project. In this case, the forensics’ SME would have been able to spot the Band-Aid fix and alert the owner to the problem it would pose.


Based on the considerable experience of Florida-based Liberty Building Forensics Group, certain factors are more critical than others in avoiding catastrophic moisture and mold problems. Warm, humid climates offer a set of unique conditions that tend to dramatically increase the potential for moisture and mold problems in four distinct and specific areas:

  1. Building envelopes that are not sufficiently tight.
  2. Building envelopes that are not water-resistant.
  3. An improperly sized air-conditioning system coupled with improper dehumidification.
  4. Inadequate building pressurization and infiltration control.

Each of these factors brings a unique set of issues to the problems associated with moisture control.

At face value, these four items would appear to be very well understood by the design and construction industry. After all, a plethora of published information, training, and how-to materials exist to explain what these four items mean and what is required to avoid problems in these areas. Yet these same issues are at the heart of some of the largest and most catastrophic mold and moisture problems in the world.


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