Here is an all too common scenario: A design and construction team is awarded a new hotel project. The brand 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 the 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 brand 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 theory behind brand design and construction standards is to provide assurances that the hotel is built to requirements that meet the brand’s expectation for aesthetic, operational and building performance. Brand standards portray themselves as a repository of lessons learned and of what should be done (and, by implication, what should not be done) to make the hotel work. However, theory proves contrary to actual practice because design standards are developed on a global basis, and they typically do not take into consideration specific needs and limitations of regional climates.

These violations in design standards have been shown repeatedly to result in extensive and costly mold and moisture problems in hotels.

Scenario: Hotel in a Humid Climate
Consider a 140-room hotel in a warm and humid climate in Texas. Shortly after construction had been completed, the hotel began to experience significant mold and moisture problems that resulted in a more than $5 million of damage claim against the general contractor. Brand standards for the hotel required that the mechanical system provide roof top units (RTUs) for conditioning of the corridors with 10 percent additional outdoor air for building pressurization. The guest rooms were required to have packaged terminal air-conditioning units (PTACs) with outdoor louvers to “balance with the building exterior air.”

In other words, if air was 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 and humid climates, such as Texas, Florida and many Southeastern states up the Atlantic coast. In these climates, the brand standards can lead to mold.

Mold on drywall demising wall found after removal of VWC in a 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.

Removal of drywall from the demising wall shows the path of warm, humid air passing through the metal stud punchouts.

Measurements of relative pressurization confirmed the cause of visual evidence of mold growth behind the VWC. With all HVAC systems operating (RTUs, PTACs and toilet exhausts), the guest rooms and wall cavities were under high negative pressure relative to outdoor air. Even with the toilet exhaust fans turned off, guest rooms were barely under positive pressure, and some were still under negative pressure. Negative pressurization, as a result of misapplication of brand standards, results in drawing in of warm, humid air that leads to mold growth. 

Know the Design and Construction Elements at Risk
Ideally, the design and construction teams responsible for executing these plans should be able to know which elements are at risk in certain climates. Brands claim their standards are only guidelines. They believe the designer or contractor onsite is ultimately responsible for interpreting how the regional climate might impact brand standards. But in reality, the brand has such influence on the way design peer reviews are conducted that design and construction teams typically migrate to brand standards adherence, even if it is contrary to best practice for that climate.

The authoritarian language often found in brand design and construction standards states:
  • no variance to the guest room will be allowed;
  • the design and construction guidelines are minimum standards across all climate zones;
  • regulatory and codes are not to reduce the intent of the guidelines; and
  • any changes made require approval from the brand.
This creates significant inertia against the contractor or designer initiating or implementing modifications to the design and construction guidelines even if they are required for the project site climate zone.

The brand standards are very specific and intricately tied to the economics of the project. Modifying the design and construction guidelines for the project in Texas would have added significant construction costs and therefore impacted the project economics. For example, the cost of 100 percent outside air units is greater than the recirculating system required by the brand standards. Modifying the central exhaust to individual fans also would cost more.

A vacuum appears to exist in the institutional memory of design firms, construction firms, ownership groups and brands that are currently flooding the marketplace. What was known to work well 10 years ago has been forgotten in today’s hotel design and construction. This poses a significant risk of new hotel failures that could mirror what was experienced in the 1990s in warm, humid climates. The combination of continuous exhaust, makeup air that is not ducted to the guest room and the use of impermeable wall coverings can result in catastrophic hotel moisture and mold problems.

The combination of these factors today means the hospitality industry is seeing a recurrence of mold and moisture problems with the recent emergence of new hotel construction.

The solution to the clash between brand standards and regional best practices includes the following.
  1. Contractors need to assert that specific 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.
  2. Brands must accept the fact that certain combinations of brand 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 prevent costly delays to the project.
  3. 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.

George DuBose, president of Liberty Building Forensics Group, Orlando, Fla., has more than 25 years of experience in diagnosing, correcting and remediating moisture-related mold problems in buildings. Norman Nelson, P.E., has more than 30 years of experience solving building-related IAQ and moisture and mold problems, and has conducted technical peer reviews of new facility designs representing more than $500 million in construction costs. Richard Scott, a senior forensic architect and vice president with Liberty Building Forensics Group in Gainesville, Fla., has more than 35 years of architectural experience and has conducted IAQ and forensic investigations in more than 300 hotels, resorts, commercial office buildings, government facilities, hospitals, schools and multi-family residential buildings.