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BCIT Citations Collection

Application of hygrothermal analyses to optimize exterior wall design
Proceedings of 2nd International Conference on Research in Building Physics: 14 September 2003, Leuven, Belgium. The design of exterior walls in a building envelope for optimum moisture management is a challenging task. Many conventional methods or local practice guidelines are available for this purpose, based primarily on regional traditions and with limited performance assessment records. In recent years, new wall systems and unconventional materials have been introduced in every part of North America for reasons such as aesthetic appeal, cost-effectiveness etc. However, neither the long-term moisture management performance of these new wall systems nor the uses of unconventional materials have been assessed rigorously. The primary reason for this lack of such assessment is the absence of a design-oriented technical routine toperform the task. Recent studies at the Institute for Research in Construction (IRC) / National Research Council (NRC) of Canada, show that such an assessment is possible with the use of an advanced hygrothermal modelling tool, such as hygIRC, developed in-house at IRC. This paper presents results from hygrothermal modelling and discussion on walls with the four different cladding systems: stucco, exterior insulated finish systems (EIFS), masonry and siding. These walls were virtually exposed to several North American climates. Their hygrothermal responses were assessed with a novel indicator, called the RHT index, which is derived from relative humidity and temperature. The results and discussion presented in this paper clearly show the need and usefulness of an integrated design methodology for the moisture management of exterior wall systems that can help to optimise various design considerations., Conference paper, Published. A version of this document is published in: Research in Building Physics, Leuven, Belgium, Sept. 14-18, 2003, pp. 417-426.
Assessment of building retrofit options using hygrothermal analysis tool
Proceedings of 7th Symposium on Building Physics in the Nordic Countries: 13 June 2005, Reykjavik, Iceland. As the stock of buildings in our society ages, it is expected that there will be an increase in building envelope rehabilitation work. Such activities represent an ideal opportunity to modify the existing wall system to improve building envelope durability and energy efficiency. This could be done by addition of insulation and sealing air leakage paths. However, there is very little information available on how to assess the moisture and energy (i.e. thermal) performance of retrofitted building envelope assemblies and select the optimum retrofit options that will maximize the long-term moisture performance and the energy efficiency of the retrofitted building envelopes together. This paper presents the findings from a study that has used a two-dimensional hygrothermal simulation tool, hygIRC-2D, to assess moisture and energy performance of retrofitted masonry walls used in high-rise construction for both residential and commercial types of buildings at various Canadian locations. The results from the simulations indicate that, if heat, air and moisture transport properties of the materials and the airflow characteristics of the systems can be defined properly a hygrothermal simulation tool can be used to evaluate the moisture and thermal (i.e. energy) performance of various wall systems and associated retrofit options., Published. A version of this document is published in: 7th Symposium on Building Physics in the Nordic Countries, Reykjavik, Iceland, June 13-15, 2005, pp. 1139-1146.
Development and benchmarking of a new hygrothermal model
Proceedings of 11th International Conference on Durability of Building Materials and Components: 11 May 2008, Istanbul, Turkey. This paper presents a new hygrothermal model (HAMFit) for simulating the transport of heat, air and moisture across building envelopes. The model is based on partial differential equations solved simultaneously for air velocity, temperature, and moisture distributions for given interior and exterior conditions using finite-element-based commercial software called COMSOL Multiphysics and MatLab. The model is benchmarked using internationally-published numerical model test cases., Conference paper, Published. A version of this document is published in: 11th International Conference on Durability of Building Materials and Components, Istanbul, Turkey, May 11-14, 2008, pp. 1-8.
Hygrothermal modeling of aerated concrete wall and comparison with field experiment
Proceedings of 3rd International Building Physics Conference: 27 August 2006, Montreal, QC. A two-dimensional heat, air and moisture transport model called hygIRC is adapted to simulate a well-documented field exposure of an aerated concrete wall section. Difficulties are encountered due to a few missing information on boundary conditions of the exposure and hygrothermal properties of aerated con-crete. The paper presents how these inadequacies were overcome to simulate the hygrothermal behavior of the wall section. Appropriate assumptions were made due to justifiable reasons. Then the model provides temporal and spatial distributions of temperature and relative humidity for an extended period that are in ex-cellent agreement with the documented field data. The paper presents the justifications for the assumptions and the comparison of experimental and simulation results., Conference paper, Published. A version of this document is published in: 3rd International Building Physics Conference, Montreal, QC., August 27, 2006, pp. 321-328.
Hygrothermal performance of exterior wall systems using an innovative vapour retarder in Canadian climate
Proceeding of the 4th International Building Physics Conference: 15 June 2009, Istanbul, Turkey. This paper provides highlights of the research work carried out at the National Research Council Canada, Institute for Research in Construction on assessing the hygrothermal performance of wall systems that included this innovative vapour retarder (Note: Vapour Barrier in Canadian terminology is equivalent to Vapor retarder in US terminology). The performance of walls was assessed when subjected to eastern coastal climate conditions of Halifax, one of the four Canadian climatic locations used in this study. A wood-framed stucco clad wall was the reference assembly. Results from different cases based on the variation of vapour control strategies and their effect on the hygrothermal performance of the wall systems are analysed. The results for the Halifax climate location indicate that the installation of a humidity controlled, innovative vapour retarder is a recommendable solution for the envelope design of residential buildings of these locations with moderate or high water vapour permeance of the interior paint. In this study, the advanced hygrothermal tool, hygIRC, was used to perform the hygrothermal performance analysis of the wall systems., Peer reviewed article, Published. A version of this document is published in: 4th International Building Physics Conference, Istanbul, Turkey, June 15-18, 2009, pp. 1-8.
Hygrothermal properties of exterior claddings, sheathing boards, membranes and insulation materials for building envelope design
Proceedings of Thermal Performance of the Exterior Envelopes of Whole Buildings X International Conference: 02 December 2007, Clearwater, Florida. Testing was conducted to determine those construction material properties that affect the movement of heat, air, and moisture in building envelopes. The paper reports the density, thermal conductivity, equilibrium moisture content, water vapor permeability, water absorption coefficient, liquid diffusivity, and air permeability of twenty-three building materials commonly used in North American including: exterior claddings, exterior sheathing boards, membranes and insulations. The paper also discusses the experimental and analytical procedures used to determine these properties., Conference paper, Published. A version of this document is published in: Proceedings of Thermal Performance of the Exterior Envelopes of Whole Buildings X, Clearwater, Florida, Dec. 2-7, 2007, pp. 1-16.
Use of hygrothermal numerical modeling to identify optimal retrofit options for high-rise buildings
Proceedings of 12th International Heat Transfer Conference: 18 August 2002, Grenoble, France. Using numerical modelling to simulate and predict the hygrothermal (i.e., combined thermal and moisture)performance of building envelopes is very recent. Key questions include: how to model accurately coupled heat-air and capillary moisture transports in building envelope components; a satisfactory definition of a set of representative environmental boundary conditions to be used for long-term hygrothermal calculations; how to characterize the moisture- and temperature-dependent properties; the effect of aging and cyclic environmental conditions on porous building materials; and how to develop sound criteria to predict the moisture durability of building envelope components. This paper presents the findings of a research project involving detailed hygrothermal modelling. The heat, air and moisture results demonstrated that the in-house model could be adapted successfully for high-rise building calculations. The findings also show how the long-term hygrothermal performance of typical wall systems can be assessed using numerical modelling. A short description of an advanced in-house heat, air and moisture model, hygIRC, is also presented., Conference paper, Published. A version of this document is published in: 12th International Heat Transfer Conference, Grenoble, France, Sept. 18, 2002, pp. 165-170.
Variations in the hygrothermal properties of several wood-based building products
Proceedings of Second International Building Physics Conference: 14 September 2003, Leuven, Belgium. A systematic investigation of the hygrothermal properties of a number of oriented strand boards, plywood products, wood fibreboards and composite wood sidings has resulted in new information on the variations of thermal conductivity, water vapour permeability, moisture diffusivity, sorption- desorption-suction isotherms, water absorption coefficient and air permeability of these classes of products in North America. The experimental and analytical procedures used in the investigation are all based eitheron International Standards or on well-documented and peer-reviewed approaches. This paper presents the description of the products in each category and detailed information on the range of properties. The details include, density and temperature dependences of thermal conductivity,dependence of vapour resistance factor on relative humidity, dependence of moisture diffusivity on moisture concentration, equilibrium moisture content for the full range of relative humidity, variations in the water absorption coefficients and dependence of air permeability on pressure difference., Conference paper, Published. A version of this document is published in: Research in Building Physics, Leuven, Belgium, Sept. 14-18, 2003, pp. 35-42.
Verification and validation
The hygrothermal performance of building envelope systems is dictated by their responses to combined heat, air and moisture fluctuations produced by exterior and interior conditions. Research has focused on both laboratory experimentation and modeling of envelope systems by computer programs (hygrothermal tools). Experimental studies played a crucial role in the development of hygrothermal tools, and continue to offer useful information for their improvement. To be used with confidence, however, hygrothermal tools must be verified and, if possible, validated. To date, no comprehensive schemes for benchmarking hygrothermal tools exist as, for example, exist for energy simulation tools. Three comparisons are typically used to show the practical merits of simulation tools: inter-model, analytical, and empirical. This paper demonstrates how confidence in a 1-dimensional hygrothermal simulation tool can be built by such comparisons, and proposes them as the basis for a verification and validation methodology., Research report, Published.