Brand Demands: Can These Be The Cause of Catastrophic Mold Problems?
The theory behind design and construction (D&C) standards is to provide assurances that the hotel is built to requirements that meet the brand’s expectation for aesthetic, operational, and building performance. D&C 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 in this case because D&C standards are developed on a global basis. They typically do not take into consideration specific needs and limitations of regional climates. In fact, it has been found that these D&C standards often don’t comply with recommended building practices for certain climates at all. These violations in the D&C standards have been shown repeatedly to result in extensive and costly mold and moisture problems in hotels.
In the case of 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. Liberty’s 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 guestrooms were and wall cavities were under high negative pressure relative to outdoor air. Even with the toilet exhaust fans turned off, guestrooms were barely under positive pressure, and some were still under negative pressure (see Figure 1). Negative pressurization, as a result of misapplication of brand standards, results in drawing in of warm, humid air which leads to mold growth.
Figure 1: Results of pressurization measurements in 14 hotel guestrooms distributed throughout the building (different floors and orientation). With all HVAC systems operating, all rooms were under negative pressure relative to the outdoor air (yellow columns). Turning off the toilet exhausts allowed nine rooms to become slightly positive or neutral (blue columns), but well below the five pascal positive limit (dotted red line) recommended for warm, humid climates. Five rooms remained slightly negative even after the toilet exhausts were turned off.
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 D&C standards are only guidelines. They believe the designer or contractor on site is ultimately responsible for interpreting how the regional climate might impact D&C standards. In reality, however, the brand has such influence in 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.
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 D&C 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% outside air units are greater than the recirculating system required by the brand standards. Modifying the central exhaust to individual fans would also cost more.
There seems to be a vacuum that exists in the institutional memory of design firms, construction firms, ownership groups, and brands that are currently flooding the marketplace. What was known to work so 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. Consider the design and construction guidelines produced by a large theme park owner in the 1990s. It has been known since that time the combination of continuous exhaust, makeup air that was not ducted to the guest room, use of impermeable wall coverings can result in catastrophic hotel moisture and mold problems (see Figure 2).
Figure 2: Example of a “Mildew Tree,” developed by LBFG staff, J. David Odom, to predict mold (“mildew”) problems. (This is a concept tool and does not fully describe all of the interacting factors that are associated with these decisions, including: code, wall finishes and factors related to waterproofing.)
If the combination of these factors continues to occur, then it means that the hospitality industry is going to continue to see a recurrence of mold and moisture problems with the recent emergence of new hotel construction.