Buildings that passed former air tightness standards with flying colors just a few years ago would now fail dismally under more recent, aggressive standards in codes such as IgCC and IECC.
Innovation incentives and high performance requirements may be well-intentioned but can lead to significant confusion – not to mention unachievable benchmarks and possible building failures.
These codes and initiatives are often driven by empirical laboratory analysis, which does not always translate well to field applications. Codification is then pushed out to designers and contractors who unfortunately must interpret puzzling requirements that often don’t make sense in the field.
Many designers are unfamiliar with how the interaction of air barrier and HVAC systems affects compliance and air infiltration, or with how this interaction can escalate the potential for moisture damage. They are unaware of how often air barrier non-compliance and moisture problems are due to contributing factors such as original system design.
“Overly complex and problematic exterior wall systems, due to a market-driven design emphasis on energy savings, high performance, and innovation, inevitably lead to increased risk and liability in all climates, and concern about mold and moisture damage in warm/humid climates,” emphasized George DuBose, president of LBFG.
LBFG has been called upon frequently to perform building forensics and diagnostics services on structures suffering from moisture and mold problems.
They recently assessed moisture-related problems in on-base and off-base soldier housing in a warm, humid climate, evaluating the military homes to identify any HVAC and/or building envelope deficiencies. If moisture damage was identified, they were to determine if the source was water or air, and remediate any observable mold growth.
The HVAC systems in up to 100 homes were evaluated, and building envelope testing was performed in up to 30 homes. Cumulative test results indicated that no additional means were necessary to tighten the envelope, nor were additional provisions necessary to provide ventilation for acceptable indoor air quality.
Interestingly, however, based on the new standards, this construction would have been considered too leaky and required remediation to tighten the envelope.
It is undeniable that current air barrier expectations are a far cry from reality. The gap must be narrowed if building failures and inefficiencies are to be avoided.