When it comes to building performance, too much of a good thing can become a bad thing. Humidification to provide medical patient comfort is a good thing. Frost and ice damage due to that same humidification is not so good.

When new building code requirements require high performance and innovation incentives, such as those found in green building rating systems, significant confusion and some building failure will ensue. This is the current situation that designers and contractors are facing in wall system air barrier design and performance. 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 hot/humid climates.

Significant in 2012 was the issuance of the International Green Construction Code (IgCC). This provided a vehicle for codifying many elements of the U.S. Green Building Council (USGBC) Leadership in Energy & Environmental Design (LEED)® rating systems and ASHRAE standards that have been issued over the last decade. (Most of them have been released in just the last two years.)

The development of codes such as the IgCC are often based on collaboration through cooperating industry professional society sponsors. Despite the benefits of collaboration, high performance and innovation initiatives are often driven by code empirical laboratory analysis, which sometimes does not translate well to field applications. This codification is then pushed out to contractors, who unfortunately must then face the task of interpreting sometimes puzzling requirements that don’t always make sense or work in the field.

Continue Reading AIR BARRIERS: EXPECTATIONS VS. REALITY
 — THAWING A FROSTY RELATIONSHIP

 

Construction of a large luxury resort located in a warm, humid climate was coming to a close during the summer. Because the vinyl wall covering on the interior side of the exterior walls had an impermeable finish, it functioned as a vapor retarder (also referred to as a vapor barrier).

The HVAC system consisted of a continuous toilet exhaust and packaged terminal air-conditioner (PTAC) units. The outside air exchange rate in each guest room averaged six times an hour, all from infiltration.

In this case, problems developed both inside the building and inside the wall.

The combined effect of excessive outside air infiltration and an improperly located vapor retarder caused $5.5 million in moisture and mold damage, even before the facility was opened (Figure 1). If these same design combinations had occurred in a more temperate climate, the problems would have been limited to increased energy consumption and possible complaints about guest comfort.

This is one example of how hot, humid climates present unique challenges that are often overlooked by the design and construction community. However, challenges also occur for buildings located in other climates. Meeting these challenges depends on understanding a building’s local climate conditions and how they contribute to IAQ and mold problems.

 

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INTRODUCTION

An alarming number of new buildings suffer from moisture and mold problems. The risk of failure is highest in—but not limited to—cold, temperate, warm-humid, and hot-humid climates. The debate on why some buildings fail and others do not, as well as who is responsible for these failures and how to fix them, rages on. Instead of being aired in architecture schools and at engineering society meetings, however, this debate goes on in courtrooms and mediation hearings, among highly paid expert witnesses and lawyers—not among people who should be preventing failures, but among those who are rewarded by their occurrence.

The building industry seems baffled about the prevalence of building failures. Many wonder why the rate of building failures is not declining despite better technology, increased training, and more sophisticated building systems. It is not due to indifference or ignorance. We know we can prevent buildings from failing because we can fix them once they do fail. The primary reason we are not coming to grips with this far-reaching problem is simple: the design professionals entrusted with building performance are not receiving adequate feedback on the performance of their previous buildings.

Without that feedback, we do not know why some buildings work well and others do not, despite being apparently designed the same way. Metrics may say that the industry did a good job, yet clients keep complaining about building failure and the construction litigation business keeps growing. Until architects and engineers receive better performance feedback, they will have neither the ability nor the incentive to change.

 

Continue Reading Why Buildings Fail