Taking the Guess Work Out of Envelope Design
Wall system design is increasingly challenging for builders and architects, as modern building practices have changed and codes have become much more stringent to meet energy efficiency requirements. Uncertainty about moisture risk associated with innovative envelope approaches can hinder adoption of new approaches and technologies.
A new beta version of a web-based tool, the Building Science Advisor (BSA), developed jointly by the U.S. Department of Energy (DOE) Energy Efficiency and Renewable Energy Office and officials at the Oak Ridge National Laboratory (ORNL), can provide guidance to building professionals on how to minimize moisture risks in low energy, high performance homes.
Developed with Builder Concerns in Mind
In developing the BSA tool, officials at DOE and ORNL were guided by research conducted from Home Innovation Research Labs on the top challenges builders expressed about energy efficient construction:
- Moisture performance of energy efficient walls
- Moisture performance of energy efficient attics
- Understanding the impact of new code requirements on long-term performance
- Proven durability of new products and materials
DOE and ORNL worked for about 2 years in consultation with experts in building science and researchers to develop the BSA – viewed as a scalable solution to get expert knowledge into the hands of all industry professionals. “The tool is designed to be a moisture management reference and learning tool for builders, architects, contractors and others in the build environment,” according to Simon Pallin, Ph.D, Research and Development Associate at ORNL. “We know that new materials and new types of assemblies are increasingly used in residential building and that there’s a potential risk for moisture accumulation that can cause problems in the building envelope,” said Pallin. This new tool will allow building professionals to plug in a summary of the system design, such as sheathing, water/air barrier, air tightness level, etc. to predict the moisture durability performance of a wall system.
ORNL says this is the first application of an expert system for moisture management in buildings. “The Building Science Advisor is needed because building professionals don’t always have access to building scientists who can readily answer their questions about wall system design,” Pallin notes. Based on the input and knowledge of the researchers and building scientists who contributed to its development, the BSA will enable users to make informed decisions to minimize risks and confidently build homes that can reduce the energy use of a home by at least 60 percent.1
Informing Envelope Best Practices
The BSA was developed with the guiding principles of optimum moisture management practices, which vary by climate zone (see chart at right). Hygrothermal simulation are used to identify the conditions under which assemblies would be most susceptible to moisture-related problems based on the materials used and the predicated moisture durability performance is assessed. Once the components of the assembly are entered into the tool, it produces guidance that addresses how to achieve the best moisture durability.
Pallin notes that the tool will be modified and enhanced as it’s used by building professionals. “The feedback from stakeholders who’ve tried the tool thus far has been positive it will continue to evolve and get better and better,” says Pallin. “This is an opportunity for builders to get expert judgement in order to have a level of confidence in the practicality and durability of wall system design.”
1. U.S. Department of Energy, Office of Energy Efficiency and Renewables, ORNL Presentation. https://energy.gov/sites/prod/files/2017/04/f34/2_1112_Jackson_031417-1400.pdf
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