PATH-D

PATH - A Public Private Partnership for Advancing Housing Technology

Standards and Metric Research

PATH-D

[IMAGE: NIST SPHERE]Durability Research

The goal of the PATH-sponsored NIST durability research is to develop and implement a dependable methodology for accurately predicting the in-service performance of building materials exposed in their intended operating environment and subjected to outdoor weathering in less than real time. The first two building products selected for research are sealants (such as caulk) and coatings (such as paint and stain); the premature failure of which can result in high repair and renovation costs. Read about the NIST SPHERE, a revolutionary device to determine quickly and accurately the damage to polymer coatings, materials and structures exposed to the sun's ultraviolet (UV) rays, temperature and humidity.

Durability-Related Decision Tools

NIST is conducting a parallel effort to communicate the economic value of improved durability. The National Economic Service-life Tools (NEST) is a set of online tools that combines regionally specific economic conditions (local labor rates, local cost of materials) with the regionally specific durability to produce accurate, specific local estimates of the savings associated with increased durability. These tools are being used to assess the economic benefit of several types of common residential components of the building envelope including roofing, siding, windows, and garage doors. Go to NEST Toolbox.

Durability Research Approach

The approach is to use controlled laboratory conditions in evaluating the dose-damage response of exposed materials.

Dose involves all of the major weathering elements including ultra-violet radiation, temperature, humidity/moisture content and mechanical load.
Damage is any chemical and mechanical change in these materials with dose.

The importance of each factor, acting separately or in all possible combinations, is evaluated. This laboratory constructed database of dose-damage data is used to construct damage accumulation profiles for each laboratory weather history. Separate outdoor exposure experiments are being conducted to validate the laboratory generated models. These outdoor exposure environments and materials damage are monitored in exactly the same way that the laboratory exposure environments are characterized. Comparing the predicted damage accumulation pattern from the laboratory database of dose-damage data with the outdoor exposure will verify the validity of this approach. This dose-damage approach has a well-established history of success in the biomedical and electronics communities.

Attempting to solve the service life prediction problem is a significant basic research undertaking. This effort involves funding from three federal agencies -- HUD/PATH, Department of Commerce, and US Department of Agriculture -- and cooperative research agreements with 18 companies, with additional funding support from the Air Force Research Laboratory at Wright Patterson Air Force Base, the Federal Highway Administration, and the Smithsonian Environmental Research Center. These true partnerships with industry and other Federal agencies ensure rapid progress and technology transfer.

Service Life Prediction of Polymeric Coatings Web Site

Workshop on Sealant Durability September 25-26, 2000