Framed Walls: Insulation, Humidity, and Risk

With an increasing trend towards higher building envelope insulation levels to meet more stringent building energy requirements many designers have looked to split insulated framed wall assemblies as a means of achieving higher building envelope R-values. However, higher levels of insulation, when not entirely outboard of the structure, often raises questions about hygrothermal performance. The selection of weather resistive barriers (WRB) and insulation are important considerations when trying to balance hygrothermal performance with costs, wall thickness and energy targets. Designers often rely upon collective wisdom to help select materials for their wall assemblies. This presentation will discuss why some of these practices are too simplistic and outlines a holistic approach to hygrothermal modeling for framed wall assemblies in both the field area of the wall and at the framing.

Learning objectives:

  1. Learn how hygrothermal analysis can be applied to design limits that will aid designers and decision making on projects.
  2. Learn about key findings from the assemblies that have been tested for several Canadian climates.
  3. Understand hygrothermal design limits such as insulation ratio, maximum indoor humidity load, and maximum allowable rain penetration are introduced with examples for consideration and discussion.
  4. Learn the effects of vapour permeance and how it relates to the building envelope.

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Ivan Lee, P.Eng., LEED AP BD+C

Ivan’s experience includes heat transfer analysis and hygrothermal modelling of building envelope assemblies to determine the risks of damage from moisture accumulation. He has been involved with various projects including condensation analysis of window wall and curtain wall glazing systems, as well as 3D thermal modelling to assess thermal bridging details for the Building Envelope Thermal Bridging Guide (BETB Guide) and the Guide to Low Thermal Energy Demand for Large Buildings (Low TEDI Guide).