Sunset Ridge Office Building

Title: Sunset Ridge Office Building

Award Category: Exterior Wall

Project Address/Location

1515 Des Peres Rd

St. Louis, MO 63131
United States

Submitted By: Aaron Rosen

Company Info

RosenBEC

400 Chesterfield Center, #400

Chesterfield, MO 63017
United States

636-322-6122

[email protected]

Project Description and Background: Sunset Ridge is a 3-story, 48,000 ft2 office building located St. Louis, Missouri. Shortly after substantial completion, mold growth was observed on the interior finishes of the 3rd floor. Fortunately, the interior finishes had not yet been installed on the 2nd floor thus there wasn’t a food source for mold growth. This also allowed for viewing access of the window perimeter conditions and it was apparent there were beads of water above and below the horizontal strip windows, primarily limited to only the south side of the building. It was reported this occurred only after summertime rain events, which continued to leak for several days thereafter. The project stakeholders were notified of the issue at hand. There were differing opinions with respect to how to conduct the forensic investigation. Accordingly, there was disagreement amongst the project stakeholders with respect to how to identify the source(s) of the problem. RosenBEC was tasked with performing an impartial forensic investigation and providing conclusive evidence that explained the reported problem.

Scope: By performing hose water testing, RosenBEC was able to rule out that the reported problem was the result of water leakage. This initial testing was performed in the fall when the outside weather conditions were cool with a relatively low amount of water vapor in the air. Due to the suspicion of summertime condensation and in anticipation of future testing, RosenBEC took a variety of quantitative measurements during this testing as a baseline comparison (e.g. air temperature, relative humidity, material surface temperatures). While waiting to evaluate the hypothesis of summertime condensation, RosenBEC reviewed the project documents to develop and present conceptual repair options to the owner. It then became apparent that the horizontal strip windows were not installed in conformance with the manufacturer’s installation instructions, which allowed the system to be either interior or exterior glazed. The installed windows were a variation of these options, and when compared to the installation instructions, would be considered either upside down or inside out. The configuration of the windows was then discussed with the manufacturer, but they were not able to provide any commentary or documentation to attest the performance of the as-built configuration. To further compound the issue and hand, the building owner needed to proceed with a repair plan for the 2nd floor because they had signed a new tenant that was preparing to install interior finishes. Once the environmental conditions were conducive to recreating the reported problem, the same exact hose water test procedure was performed at the same location that was previously tested. Although water leakage was not observed (again), shortly after completion of the testing it was apparent that droplets of water were forming above and below the windows. Based on the results from this testing, this was believed to have been a re-creation of the reported problem. The stakeholders proceeded with dispute resolution because they could not agree on who was responsible for the repair costs to rectify the issues at hand. While there was a disagreement with respect to interpretation of the contract documents, RosenBEC’s technical findings and analysis of the reported problem were not brought into question. Although there was not an industry standard or guide for conducting this type of forensic investigation, RosenBEC performed the work in a diligent and objective manner which ultimately provided the necessary information to the project team.

Solution: To quantify the amount of air leakage moving through the storefront window assembly, it was attempted to utilize the traditional approach of a field assembled test chamber. While the applicable industry test standards provided skepticism with respect to the accuracy of the results for the specific window configuration type, it was believed that field modifications could have been implemented to circumvent these nuances. Unfortunately, that was not the case, and the legitimacy of the air leakage readings was suspect. Accordingly, RosenBEC teamed up with a testing laboratory to develop a modified field test procedure that could reasonably provide accurate information. The goal was to adhere to the general intent of various industry recognized test standards, though deviating with respect to the means and methods for performing the test. Specifically, it was decided to pressurize the entire building as would be the case in a whole building blower door test. However, the significant deviation was the entirety of the exterior wall assembly on the 2nd floor was covered with plastic. Because the plastic was taped in a manner that it could be strategically removed, it provided a general indication for measuring air leakage through specific exterior wall conditions. RosenBEC and the testing laboratory believed the data was reasonably accurate, and to their knowledge, was a unique approach for obtaining this information.

Value: The project stakeholders suggested a repair attempt to address the condensation problem. A primary concern by the building owner was that the effectiveness of the repairs could not be validated, and if unsuccessful, they would not have been able to meet the tenant move-in deadline. In addition, their repair attempt would not address the issues associated with the window configuration. The building owner asked RosenBEC to facilitate a repair program that could be executed quickly. The general guideline was to address the deficient as-built conditions to generally comply with the original design intent, while being respectful of repair costs. RosenBEC provided commentary and feedback to help the repair contractor achieve these goals. The approach suggested by RosenBEC allowed for the existing windows to be removed, reconfigured, and then installed in accordance with the manufacturer’s installation instructions, rather than complete replacement. Once the windows were removed, and prior to reinstallation, the rough opening was flashed and prepared in accordance with the original project requirements. Based on the lack of progress the original project stakeholders were making with respect to identifying the root causes of the problem, as well as lack of participation for the repair program, it is possible the reported problem may not have been addressed properly or in a timely manner if RosenBEC was not involved. The cost to investigate and implement the repairs on this project was approximately $1 million.

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Additional Info: This project makes for a great case study discussion and lessons learned!

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