Clash of the Titans: When Hotel Design and Construction Standards Cause Catastrophic Mold Problems
Here is an all-too-common scenario: A design and construction team is awarded a new hotel project. The design and construction standards are passed on to the team. The team adheres exactly to the requirements of exterior wall design and HVAC system design only to discover during final stages of construction that the actual performance of the design is vastly different than expected. Unsuspecting hotel design and construction teams need to heed the warning: “Rigid adherence to hotel design and construction standards without factoring in specific regional and climatic conditions can result in significant mold and moisture issues in new hotel construction.”
The solution to the clash between D&C standards and regional best practices includes the following:
Contractors need to assert that specific hotel D&C requirements for hotels in certain climates cannot be violated if hotels are to avoid mold and moisture problems, even if the designers have not complied with the requirements of good climatic design in their construction documents.
Brands must accept the fact that certain combinations of D&C standards will virtually guarantee mold and moisture problems in a hotel. If the predictability of potential problems is high during the conceptual design stage, required changes can be made early on to avoid costly delays to the project.
Hotel ownership groups must realize that the economics of a project will likely change when a discrepancy is found between brand standards and best practices for a particular climate. If the actual design concepts do not match the prototype concepts provided by the brand, the ownership group will need to adopt a different set of economics for the project.
Consider this example: Shortly after construction had been completed on a 140-room hotel in a warm and humid climate in Texas, the hotel began to experience significant mold and moisture problems that resulted in more than $5 million of damage claim against the general contractor. D&C standards for the hotel required that the mechanical system provide roof top units (RTUs) for conditioning of the corridors with 10% additional outdoor air for building pressurization.
The guest rooms were required to have PTACs (packaged terminal air-conditioning) units with outdoor louvers to “balance with the building exterior air”. In other words, if there was air required by indoor pressures, then this air was to be provided by the PTAC units and not through a separate outdoor air makeup air system. The bathroom exhausts were to be continuously exhausted by roof mounted centrifugal exhaust fans.
While the brand standards did not allow impermeable vinyl wallcovering (VWC) on exterior walls it was allowed on interior walls. For all practical purposes these sets of brand design and construction guidelines would have worked in nearly all areas of the country except for warm/hot humid climates, like Texas, Florida and all Southeastern states in between and up the Atlantic coast. In these climates the brand standards can lead to mold (see Figure 1 and Figure 2).
Figure 1: Mold on drywall demising wall found after removal of VWC in this hotel room. The toilet exhaust from the bathroom to the left was drawing warm, humid outdoor air through the cavity spaces of the metal stud wall. The cold air from the PTAC unit, which was installed in the sleeve below the window to the right, cooled the moist air behind the VWC to the point of condensation. The condensation wetted the drywall and caused mold to grow in a “plume” that matched the throw of cooled air from the PTAC unit.
Figure 2: Removal of drywall from the demising wall shows the path of warm, humid air passing through the metal stud punchouts. Note mold growth (arrow) along that path.
The combination of these factors means that the hospitality industry is seeing a recurrence of mold and moisture problems with the recent emergence of new hotel construction. The development of brand D&C standards are, in some cases, being developed in a vacuum of what good practice dictates by in house resources that are not familiar with differing considerations required for different climates.