BTC Helps Solve Mystery of
Crumbling Buildings in Seattle

Seattle has a problem: a large number of its recently constructed buildings are experiencing significant moisture damage. According to an informal 1998 survey of residential buildings in the Seattle metropolitan area,

about 70% of the buildings surveyed had moisture damage; repairs for these buildings could cost nearly $70 million; repairing all of Seattle’s building stock could cost $1 billion.

Moisture leakage has led to severe rotting in the stucco wall of this 6-year-old building in Seattle

Plagued by the failures of these buildings, Seattle officials asked the BTC for help. In a partnership with Seattle and Washington State University, BTC researchers have set out to determine what is causing the moisture damage and are helping to develop repair solutions.

Moisture damage problems are not limited to Seattle. Atlanta, Wilmington, and other high-humidity areas also report growing problems. There are several reasons for energy efficiency researchers to be concerned:

• If there is a relationship between tougher standards for building tightness and moisture intrusion, the standards may be relaxed and the efficiency gains made over the last decade may disappear.
• As moisture accumulates within the envelope, the apparent thermal conductivity of building materials increases substantially. The result is higher energy costs.
• Evaporation and condensation in building envelope components can increase energy transfer across components by up to 150% compared with transfer if the materials are dry.
• Mold and mildew can cause significant health problems.

The BTC is working with Seattle to develop building envelope designs and control strategies that achieve both energy efficiency and moisture control. The initial research phase will subject a typical western Washington building to a Seattle-like climate to assess sensitivity to moisture transport. Using computer programs to simulate the weather, researchers will also compare the relative thermal and moisture control performance of older and newer buildings.

This phase is expected to provide preliminary scientific evidence to support or refute widely held beliefs regarding moisture differences between older and newer structures. In addition, this phase should determine the effects that ventilation, indoor air quality, and energy codes have on hygrothermal performance.

The BTC's Hygrothermal Properties Laboratory will be used to measure the moisture properties of typical materials in Seattle wall systems.

In later phases, manufacturers of construction materials and envelope systems will be invited to participate in defining design guidelines for wall systems for Seattle’s climatic conditions.

For more information, contact André Desjarlais (desjarlaisa@ornl.gov).