Quantifying the Unknown: Non-Destructive Tools for Existing Buildings – IBPSA-USA Research Committee

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This videos has been made free to view for all. As buildings age, retrofits are becoming an increasingly important topic for the ever-growing and aging existing building stock. Following construction, a building’s energy footprint typically remains relatively stagnant, effectively locking-in that building’s energy usage for its lifetime. With 50% of America’s building stock built before 1980 and only 0.5–1% of existing buildings retrofitted annually, it is essential to reduce guesswork and make building energy retrofits more accessible to reduce the energy footprint of the building sector. Building retrofits are plagued by a lack of original design documentation and general uncertainty regarding the building’s envelope composition and integrity. This presentation shows the power of thermography and transient heat transfer modeling to non-intrusively characterize the thermal properties of a building’s envelope to inform energy modeling, facade design, and project appraisal.  We will describe methods to characterize existing building envelope thermal properties, followed by a preliminary methodology to identify representative thermal properties for an existing building envelope. This study provides a verified computationally-driven methodology to identify representative thermal resistance and thermal mass of a façade to inform retrofits and repairs. This study also places context on the characterization process of building wall constructions and displays that most assemblies can be characterized with approximately two days of measurement data.  This work is a foundation for future research to characterize and understand the impact of defects in envelopes and bridge the gap between the auditing and energy modeling processes.

Understanding building envelope hygrothermal performance is an essential foundation of building sciences, mainly due to the envelope’s role as a boundary layer for exterior environments, as well as container and regulator of internal microclimates. We describe select Non-destructive Testing (NDT) techniques for building envelope scanning and surveying for thermodynamic diagnostics. The investigation focuses specifically on reviewing six NDT techniques: Ground Penetrating Radar (GPR), Light Detection and Ranging (LiDAR) / Laser Scanning, Ultrasound, Close-Range Photogrammetry and Through-Wall Imaging Radar (TWIR). The aim is to identify knowledge gaps in terms of their use in accurately characterizing envelope compositions for further integration in Building Energy Modeling (BEM). Each technique was evaluated according to set categories imbibed from the American Society of Heating, Refrigerating, and Air Conditioning Engineering (ASHRAE) Standard 211 that showcases the technique’s ability to extract various relevant information. A framework is then developed to inform users on how to use hybrid NDT-based workflows applied in building envelope energy audits. We will discuss the possibilities of utilizing NDT in large-scale audit automation, BEM integration, and developing built environment policies focusing on increasing existing building performance through retrofitting design.

Learning Objectives:

  1. Describe the methodology used to characterize as-built facade components.
  2. Understand the scope of the building envelope in terms of ASHRAE Standard 211P
  3. Understand the current state of different NDT Techniques in terms of surveying the building envelope.
  4. Apply thermally equivalent facade components for energy simulation and load calculation.


Tyler Pilet is a mechanical engineer and building technologist focused on fault detection and characterization of building envelopes.  Currently, Tyler is a building energy efficiency engineer at Pacific Northwest National Laboratory researching residential building applications.  While his research focuses on the built environment, Tyler’s main interest is addressing problems related to equity, access, and well-being of people living in and interacting with buildings.

Yasser El Masri is an architect who specialized in sustainable design and building technology and is pursuing his Ph.D. in Architecture with a concentration in High-Performance Buildings at Georgia Tech. Prior to starting his Ph.D., he had received his Master of Sciences in Sustainable Design from the University of Texas at Austin on a Fulbright Scholarship. He is interested in building science and building energy policy and the grander effects of these issues on human lives including and beyond the quantitative aspects. Currently, he is also pursuing a Master of Sciences in International Affairs at the Sam Nunn School at Georgia Tech where he intermarries his work in building science with that of state-level policymaking on a national and international level.

existing building stock, existing buildings, building retrofits, retrofits, hygrothermal performance, building envelopes