Highly Insulated Wall Systems with Exterior Insulation of Polyisocyanurate under Different Facer Materials: Material Characterization and Long-Term Hygrothermal Performance Assessment

The application of exterior insulation in both new construction and retrofits is a common practice to enhance the energy efficiency of buildings. In addition to increased thermal performance, the rigid insulation can serve to keep the sheathing board warm and serve as a water-resistive barrier to keep moisture-related problems due to condensation and wind-driven rain. Polyisocyanurate (PIR) rigid boards have a higher thermal resistance in comparison to other commonly used exterior insulation boards. However, because of its perceived lower permeance, its use as exterior insulation is not very common. In this study, the hygrothermal property of PIR boards with different facer types and thicknesses is characterized. The material data obtained through experimental test and extrapolation is used in a long term hygrothermal performance assessment of a wood frame wall with PIR boards as exterior insulation. Results show that PIR with no facer has the smallest accumulated moisture on the sheathing board in comparison to other insulation boards. Walls with a bigger thickness of exterior insulation perform better when no vapor barrier is used. The PIR exterior insulation supports the moisture control strategy well in colder climates in perfect wall scenarios, where there is no air leakage and moisture intrusion. In cases where there is trapped moisture, the sheathing board has a higher moisture content with PIR boards with both aluminum or fiberglass type facers. An innovative facer material development for PIR boards can help efforts targeting improved energy-efficient and durable wall systems.

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An Experimental Study on the Drying-Out Ability of Highly Insulated Wall Structures with Built-In Moisture and Rain Leakage

Applied Sciences ◽

10.3390/app9061222 ◽

2019 ◽

Vol 9 (6) ◽

pp. 1222 ◽

Cited By ~ 2

Author(s):

Klaus Viljanen ◽

Xiaoshu Lu

Keyword(s):

Energy Efficient ◽

Moisture Transfer ◽

Mineral Wool ◽

Rain Event ◽

Controversial Issues ◽

Wall Structures ◽

Hygrothermal Performance ◽

The Difference ◽

Wood Frame ◽

Heat And Moisture

The recent research on highly insulated structures presents controversial conclusions on risks in moisture safety. This paper addresses these controversial issues through investigating the hygrothermal performance of energy efficient envelope structures under high moisture loads. The experiments consist of built-in moisture and rain leakage tests in mineral wool insulated structures. A heat and moisture transfer simulation model is developed to examine the drying-out ability in both warm and cold seasons. The results show that the energy efficient structures have an excellent drying out ability against built-in and leakage moisture. The difference in the drying ability is limited compared to conventional structures. A critical leakage moisture amount reaching the insulation cavity for a wood frame wall is determined to be between 6.9–20.7 g in a single rain event occurring every other day. Further research is required to target highly insulated structures, particularly addressing water vapor diffusion and convection.

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Effect of air leakage on the hygrothermal performance of highly insulated wood frame walls: Comparison of air leakage modelling methods

Building and Environment ◽

10.1016/j.buildenv.2017.07.012 ◽

2017 ◽

Vol 123 ◽

pp. 363-377 ◽

Cited By ~ 7

Author(s):

Lin Wang ◽

Hua Ge

Keyword(s):

Air Leakage ◽

Hygrothermal Performance ◽

Wood Frame ◽

Modelling Methods

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Hygrothermal performance of highly insulated wood frame walls with air leakage: field measurements and simulations.

10.32920/ryerson.14646774 ◽

2021 ◽

Author(s):

Michael J Fox

Keyword(s):

Simulation Models ◽

Field Measurements ◽

Test Facility ◽

Air Leakage ◽

Predictive Capacity ◽

Leakage Field ◽

Hygrothermal Performance ◽

Wood Frame ◽

The University ◽

Building Engineering

The thesis examines the hygrothermal performance of six types of high thermal resistance (High RSI) wall assemblies during environmental exposure and an air leakage (exfiltration) simulation test. These walls were installed in the Building Engineering Group's test facility (BEG Hut) located at the University of Waterloo. The High-RSI wood-frame walls were assessed by analyzing condensation, mould, and decay risks using the moisture content, temperature, relative humidity and heat flux data collected during the field test. These field-measured data were also used to calibrate one-dimensional WUFI® simulation models for each of the High-RSI assembly for use in future durability assessments using a range of North American climates. Methods were investigated to improve the predictive capacity of these simulation models as well as to increase their utility as a research tool. The design, construction and instrumentation details of the High-RSI study were also documented.

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