Avoid Catastrophic Mold and Moisture Problems in Hot, Humid Climates Due to Air Barrier Standard Confusion


By George DuBose, CGC; Richard Scott, AIA, NCARB, LEED AP; and Donald B. Snell, PC CIEC


Imagine the following scenario: you just designed your newest project to meet the most current whole building air leakage standards, and your mechanical engineer subconsultant has designed an HVAC system that includes one of the latest energy recovery strategies. Both factors are intended to meet high energy efficiency goals, making you proud that your firm is doing its part (amongst other things) to minimize your impact on the climate change problem.

Continue Reading Till Death Do Us Part: Preventing a Facade and HVAC Divorce When It Comes to Air Barrier Performance

The emergence of #modular construction as an option for new construction is becoming mainstream. The reasons have been reported on well. However, what has not been reported is that the modular construction industry has had mold and moisture problems, especially, when used in a warm and humid climate like the Southeast US. Both wood frame and steel frame modular construction have experienced problems with crawl space, marriage wall, and ceiling to floor cavity, condensation problems that have not only resulted in deterioration of the wood, corrosion of metal floor pans, deteriorate wallboard and mold.


The greatest risk of modular construction failures has been seen to be when this type of construction and delivery is used for hotels, student housing, senior living, soldier housing, type facilities. In general, facilities that are domicidal or multi family in nature. This is because these types of facilities have inherent similarities in a living unit that requires both an individual cooling/heating unit, bathroom exhaust, and some sort of central HVAC make up air system. In addition, there are many more modular “boxes” in these kinds of buildings increasing the number of marriage wall interior cavities and ceiling to floor cavities that otherwise might not be required in other types of modular construction. The nature of modular construction makes it difficult to repair once it is found to be damaged. Sometimes, the damage can be such that the modular building has to be deconstructed to remove damaged materials and then re-designed and re-constructed using conventional methods. This essentially makes the modular construction advantages dissolve away as the building gets converted to a traditional “stick” building.

Continue Reading Deja Vu All Over Again: Risks for Moisture and Mold Problems in Modular Construction


After over 25 years of figuring out why buildings end up as catastrophic mold and moisture building failures – there are some apparent truths that have remained seemingly unchanged.



Buildings should not be designed in silos (but they still are). Despite advances in technical understanding and higher standards for building performance, like building envelope airtightness, the design task for the building envelope is still being completed in a vacuum of other critical disciplines. On a recent project, the facade consultant was asked how their design interfaced with the overall building pressurization requirements established by the HVAC design. The answer: “We don’t consider that in our design. They do their thing and we do ours.”


Continue Reading You Can’t Fake the Funk: After 25 Years of Consulting, Here are Three Forgotten Truths about Mold and Moisture Building Failures


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.”


Continue Reading Clash of the Titans: When Hotel Design and Construction Standards Cause 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.


Continue Reading Brand Demands: Can These Be The Cause of Catastrophic Mold Problems?

“Hmm, let me think about that. Here is what I found: According to Liberty Building Forensics Group (LBFG) they have been seeing an alarming trend in moisture and mold problems in new low to mid-rise wood frame multi-family buildings.”


With improvements in wood framing technology, there has been a remarkable increase in using wood for low to mid-rise apartment buildings, dormitories, and residential condominiums. Often the first floors are podiums of steel frame, but upper floors are exclusively wood structure. Mold and moisture problems during construction are showing up due to external influences (rain) as well as internal sources (wet applied materials). Contractors must deal with repairing damage and remediating the mold to satisfy risk averse owners/developers/lenders.


Continue Reading “Alexa™, What Building Type Today has the Most Risk of Moisture and Mold Problems?”

Performance criteria for the window do not always mean that the same criteria are required for the window unit and all of its accessories – like subframes.


Specifiers mistakenly assume that the performance criteria indicated for the window unit itself applies to the entire assembly, including accessories. This can be problematic, particularly if the accessories are a critical element in the water resistance of the assembly (e.g. subframes and receptor systems). Designers typically indicate stringent performance requirements for the glazing system but fail to properly design or detail the interface between the glazing and adjacent construction. Field testing typically includes this interface at the test pressures specified for the window and leakage is common. Differentiating between window and interface leakage is difficult. Operable window and door components are not required to be tested in as stringent a manner as fixed components; however, specifiers often indicate the wrong test procedures and/or field testing is performed erroneously using the wrong procedures, resulting in false test failures.

Three major changes will impact the success of construction in Florida over the next decade. These changes began as trends during the last decade and have now evolved into requirements for construction professionals. This requires one to consider the risks of potential moisture problems and determine how to mitigate against these risk on the project. These risks are due in large part to changes in building code and how the industry is viewing the products that are being used in “green construction.”


  • There is a drive to certify products as “green” and this has substantially increased the risk of moisture problems when certain products are used. Knowing the anatomy of these products will help the construction professional alleviate this risk.
  • Green initiatives have become codified and are required now by code these for projects. It is a critical skill to be able to know the parts of the code that result in the greatest risks for causing moisture problems.
  • As the construction industry shifts from primarily a USGBC LEED® rating credit system to other rating systems like Green Globes there is a risk that comes from the introduction of confusion in the “green” marketplace and the construction industry. This confusion affects the contractor’s’ ability to communicate the needs and costs of green construction. This lack of communication can lead to budget and schedule overruns that are costly. The skilled professional will need to know which rating systems are critical for projects in humid climates and how to communicate the requirements of those rating systems to clients.

Continue Reading How to Avoid Moisture Problems When the Requirements and Practical Applications of Green Collide

The mission of designing high-performance buildings that promote sustainable objectives has led to new success stories but has also revealed vulnerabilities for potential mold and moisture failures.


The interaction between a building’s HVAC system and envelope creates an unusually high-risk area. Any deficiency in either system can cause dramatic, building-wide moisture and mold problems. Through the emergence of high-performance buildings combined with the use of certain new green products, designers and contractors have inadvertently created high-risk buildings when, in fact, the goal should be to develop high-performance buildings with the lowest possible risk of failure.

Continue Reading New Online Course Demonstrates How to Design and Construct High-Performance, Low-Risk Buildings While Avoiding Catastrophic Mold and Moisture Problems

In our work as forensic architects and engineers, we are regularly involved in litigation over stucco failures, including hotels and high-rise condo complexes. (For this article, ‘stucco’ refers to traditional portland cement plaster direct-applied to a masonry substrate, rather than using lath.)


Myths abound around stucco cracking. In truth, it is not abnormal to have some cracking with stucco, much of which can be relatively harmless. The key is paying attention to the types of cracks, and minimizing any significant issues that might lead to actual failure, including debonding, water intrusion, and mold problems. It is not a good idea to pack out stucco so thick it may end up debonding and falling on those Bentleys (and their owners) below.


Myth #3: Direct-applied stucco is easily packed out to meet a finished plane.

Continue Reading Stucco Myth #3: Direct-applied stucco is easily packed out to meet a finished plane