According to the U.S. Department of Energy Windows and Building Envelope Research and Development Roadmap for Emerging Technologies, building envelope wall energy loss in the United States accounts for about 2 quads of energy annually, costing homeowners and occupants billions of dollars. Enclosure retrofits targeting these losses can save significant energy, reduce greenhouse gas emissions, and save occupants millions of dollars over time. Older homes, built before 1992 when DOE’s Building Energy Codes Program was established, represent approximately 68 percent of the residential building stock in the country, often having significant air leakage and inadequate insulation. Homes with little to no air sealing or insulation have heating and cooling losses that can represent a substantial portion of utility bills. High performance building envelope retrofit systems are rarely selected for these applications. Current solutions are expensive and/or unfamiliar to many designers, builders, contractors, and code officials and therefore are perceived as risky. The dominant perceived risk is durability specifically related to condensation and moisture accumulation in the building envelope component. The Building Science Advisor (BSA) is a rule-based expert system webtool that was originally developed to assist building professionals to design energy efficient and durable wall systems for new construction. With the present focus being placed on upgrading the existing building stock, a retrofit module has been developed that, based on the location, existing construction, and planned retrofit strategy, provides recommendations on how to address the retrofit in a manner that will not create a durability problem. This webinar will describe the development of this tool and demonstrate its features and capabilities. Continuing Education Units (CEUS) submitted 1 hour in* Green Business Certification Inc. (GBCI) Building Performance Institute (BPI) NonWholeHouse Submitted for American Institute of Architects - AIA (HSW) Certified Green Professional (NARI & CGP) Certified GreenHome Professional (CGHP) Pillar(s): Energy, Health, Materials, Water, Place American Institute of Building Designers (AIBD) State Architect / Builder License may be applicable Building Science Institute (BSI) Verifier Passive House Consultant US (CPHC) Society of American Registered Architects (SARA) Speaker: André Desjarlais is the Program Manager for Residential Buildings Integration at Oak Ridge National Laboratory. He has been involved in building science for 50 years, first as a consultant and, for the last 32 years, at ORNL. Expertise includes building envelope energy efficiency, moisture control, and durability. Desjarlais has been a member of ASTM since 1987; he is the past chairperson of ASTM Committee C16 and was awarded the title of Fellow in 2011. He has been a member of ASHRAE since 1991 and is past chairperson of Technical Committee TC 4.4. André is also a founding director of the RCI Foundation. Lessons Learned 1. Know what types of building envelope durability and health problems are created by moisture. 2. Review the economic and environmentally sustainable impact of moisture in buildings. 3. Determine why building envelope moisture issues are more prevalent today and what issues they cause for safety. 4. Understand tools available to make informed decisions for improving wall durability, benefiting decarbonization and community welfare