Thermal Comfort and Glazing Design in Lab Spaces

Alejandra Menchaca, Payette
Lynn Petermann, Payette

Thermal comfort in labs is primarily controlled by mechanical means, allowing these systems to compensate for shortcomings in envelope performance. Moreover, because internal loads drive the energy intensity of lab spaces, minimizing winter time heat losses through glazing is not always top priority. However, the selection of a glazing system is also correlated to the thermal comfort conditions in the space, and a poor glazing choice will likely lead to the use of perimeter heating, increasing the first and operational cost of the facility. A better understanding of how thermal comfort is affected by different glazing performance criteria and geometries in the winter-time allows architects and engineers to make informed decisions when selecting a glazing scenario. This then ensures a comfortable environment for occupants without the need of supplemental perimeter heating strategies. This session will address two factors when designing a glazed opening in cold climates: radiant discomfort and downdraft discomfort, and how each correlates to the glazing U-factor and window geometry. It will cover the physics of glazing heat loss and its impact on comfort, and will rely on a new, publicly available web tool guide the audience through the decision-making process that needs to be followed to ensure a comfortable environment early in the design.

Learning Objectives

  • Identify the modes of heat transfer associated to glazing in the winter time.
  • List the unique factors of thermal comfort in a lab environment that have an effect on glazing selection.
  • Outline the variables that influence downdraft and mean radiant temperature in a space.
  • Use the Glazing and Thermal Comfort tool to evaluate the performance of glazing units in terms of the risk of radiant discomfort and/or downdraft, to decide whether perimeter heating is needed to ensure occupant comfort.


Alejandra is a Senior Building Scientist at Payette, where she leverages her background in mechanical engineering and building science to provide project teams with advanced sustainable design knowledge and energy modeling expertise, and improve the firm's understanding of the impact of design strategies and innovative solutions on building performance. She holds a Ph.D. in Mechanical Engineering from MIT, and has lectured at the Harvard GSD and at MIT.

Lynn is a practicing Architect whose foundation and interest in investigating real world issues originated from her B.A. in Chemistry at Northwestern University. Since receiving her M.Arch from the University of Texas at Austin, she has worked on several large scale undergraduate and research science buildings. She is a key contributor to Payette's Building Science thermal comfort research efforts. Lynn is currently a studio instructor at the Boston Architectural College.


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