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Canadian Property Management, v. 16, no. 5, Sept. 2001, pp. 33-34
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The Science of rain
By Sheila Noble
Published in Canadian Property Management Abstract
This article discusses the purpose and operation of a new environmental exposure facility developed for building envelope research at the National Research Council’s Institute for Research in Construction.
Resume
Cet article traite de la finalité et du fonctionnement d’un dispositif simulant l’exposition des murs aux conditions climatiques mis au point pour la recherche sur l’enveloppe du bâtiment à l’Institut de recherche en construction du Conseil national de recherches.
Testing in a new test facility at the National Research Council of Canada’s Institute for Research in Construction (IRC) could hold important trickle-down effects for North American property managers—in more ways than one.
IRC’s Building Envelope and Structure Program has developed an innovative “weather machine” for testing building materials to exact specifications under controlled
conditions—with many changes over an extended period if necessary. The chamber’s inaugural run involved testing moisture management strategies for exterior wall systems, and the results could have a significant impact on property investments in the long run. Here’s the story.
Climatic simulator one of a kind in North America
Unique in North America, IRC’s new Envelope Environmental Exposure Facility (EEEF) can simulate interior and exterior climatic conditions, including temperatures (ranging from –47 to +48ºC), humidity levels (ranging from 10 to 100% RH), and most recently, wind (up to 70 kilometres/hour). Still a work in progress, the facility will also integrate the effects of rain and some aspects of infrared radiation when it reaches its full
capability in the near future.
“The building materials industry really needed a facility capable of simulating realistic North American weather conditions to conduct research and to develop new products,” says Dr. Wahid Maref, IRC Assistant Research Officer, Wall and Window Systems. “Our chamber allows companies to test their products for performance under fully controllable conditions.”
Even better, researchers can arrange for these conditions to change to cover a wide range of conditions that may occur in the natural environment. These changes include rising and falling temperatures and humidity, and dynamic wind pressure and water spray. This
feature is an important advancement for testing because previously these conditions stayed at constant levels in less advanced facilities, which was less realistic.
In addition to changing conditions, the facility’s other innovations include:
• a weighing system that detects water evaporating from the wall by measuring the weight precisely in grams and tracking this weight over time to create a drying curve;
• a frame and gasket technique for sealing the wall specimens to the enclosure without interfering with the weighing process;
• state-of-the-art moisture meters for mapping differential drying on the face of the wall to determine the different degrees of moisture build-up throughout the system; and
• a complete data acquisition package to control and monitor experiments, integrated with a comprehensive data analysis technique for interpreting the results.
IRC-industry collaboration first test for new facility
The first test for the new facility came from IRC’s Consortium for Moisture Management for Exterior Wall Systems (MEWS). The Consortium brings together IRC researchers from the Building Envelope and Codes and Evaluation programs and 11 industry partners in a four-year project that draws to a close in 2001.
To develop guidelines for moisture management strategies in wall systems for long-term performance and durability in a wide range of climate zones across North America, the MEWS Consortium is using the EEEF to study drying behaviour at the junctions of walls with other building elements, such as windows and service penetrations.
In addition, they are comparing the thermal and moisture performance of walls in various simulated climates against the predictions for this performance of an IRC computer model called hygIRC. This combined heat, air and moisture transfer—or
“hygrothermal”—modeling tool can simulate the behaviour of materials under different climatic conditions in different areas of North America, predicting quickly and efficiently for the researchers how the materials will perform in managing moisture.
Because moisture has such wide-ranging effects, each of the MEWS industry partners represents a different segment of the building industry, including membrane, plywood and insulation manufacturers, masons, and even a prominent hotel chain, which represents the interests of the property management industry. Each member has a different interest in water’s behaviour in the wall system.
“If we understand how water behaves in the wall system, we can learn how to control it and even prevent it from entering the system,” says Maref. “This includes minimizing moisture entry into the system from construction, indoor and outdoor humidity, precipitation and human activity, and maximizing moisture exit so that no component stays wet for a long time.”
Experiment’s results exceed expectations
When researchers tested current wall assemblies in the chamber, they gathered valuable information for the MEWS team on drying behaviour, particularly how quickly the wall dries under various conditions and where it dries fastest. In addition, they created a valuable body of information with which to calibrate, or benchmark, their computer model.
“We’ve had good results from the first experiments in the facility,” says Maref. “These are proving more useful than expected in benchmarking hygIRC. And the comparisons between the results of the experiment and the model predictions have given us a lot of insight into how water redistributes itself within the wall before drying out.”
With the database of information obtained from the experiments, hygIRC is well on its way to becoming a powerful modeling tool that will allow researchers and industry partners to test different parameters for building products before going into full-scale experimentation—saving time and money in the long run.
Moisture management strategies the eventual outcome
In combination with the model, the chamber will also save the industry partners time and money by allowing them to test their building products under different sets of conditions. This testing will allow them to see how the products perform in managing moisture and how quickly they dry out afterwards. Ultimately, this information could help
manufacturers find the best blend of durability, moisture resistance and drying time before going into full-scale production and wide-scale use in wall systems.
For property owners and managers, the new systems that result from this testing could result in big savings on property maintenance and operation by ensuring that the wall system used on their building is managing moisture to the greatest possible extent. These savings would come from reducing the routine maintenance schedule necessary for the property, preventing structural problems from occurring down the road and extending the service life of the building—all of which would protect the life cycle and durability of the property investment.
Currently, IRC researchers are compiling their EEEF research plan for the next few years. The next set of experiments planned for the facility involve testing window-wall interfaces for service life and durability. The researchers will also work to integrate rain and solar heating effects into the existing climatic effects.
For more information, contact Dr. Wahid Maref by telephone at (613) 993-5709, fax (613) 998-6802, or e-mail at wahid.maref@nrc.ca.
