Overreliance of Facade Testing - Investigation of a Precast Building in the Middle East
A precast building is generally fairly easy to make airtight and prevent water intrusion - but not always. Our firm was called upon to investigate and diagnose air barrier issues in this precast building in the Middle East. The structure was unique due to its multiple projections, which dramatically increased the complexity of maintaining its airtightness. Of particular concern was maintaining the continuity of barriers, specifically in regards to air leakage.
These units had been tested according to ASTM standards (at high pressures of 300 pascals) for both air leakage and water penetration. Additionally, several rooms had also undergone blower door testing. Unfortunately, some existing leakage sites had been masked and thus overlooked. This can occasionally happen in a fully built-out room when testing results interpret different aspects of interior construction as air barriers.
Though the testing upon which the owner and design/construction team had relied reported that the building was tight enough, only isolated portions of the facade had actually been tested, and the projections had been missed entirely.
The only action that would have caught these building failures before they became significant issues would have been initiating a more robust inspection and quality control measures. In fact, it has been our experience that a field inspection protocol that assures a continuous air barrier (at the actual air barrier plane) yields better results as far as the true nature of the building’s air tightness than the most of the field testing employed in today’s buildings.
Precast buildings often contain large interior voids carrying lots of air that can communicate very easily to other parts of the building. That was the case in this building. None of the locations tested reflected the continuity of the barrier. While some tests could have revealed problematic conditions, many tests did not because of the facade.
While it is true that some of the faulty conditions in this building would have been more difficult to detect even under normal conditions - and perhaps even difficult to address in the field - none of them ever even entered into the scope of the facade testing. The root issue came down to making sure proper quality control and inspection of these conditions was being done.
It is more important for a building to maintain a complete continuous air barrier than for sections of that facade to meet specific requirements.
Although a whole building may meet air leakage requirements, the building can still lead to mold and moisture problems. With so many standards in place for air leakage requirements, it is critical to make sure the HVAC system is assisting the performance of the air barrier by maintaining accurate positive pressure. In turn, it is always easier to maintain accurate positive pressure with a continuous air barrier that has limited leakage.