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This paper will outline the construction and basic physics of vacuum insulation technology, andeconomic and technical challenges which are keeping VIP away from the building envelopeconstruction industry. At the same time, ongoing activities in Canada and around the world to bringVIP much closer to building construction industry will also be highlighted., 13th Canadian Conference on Building Science and Technology: 10-13 May 2011, Winnipeg, Manitoba

This paper describes the benchmarking exercise for the present hygrothermal model called 'hygIRC-C' against the hygIRC-2D model that was previously developed at NRC-IRC and test results of laboratory measurements of drying of four full-scale wall assemblies. The wall assemblies were representative of the North American wood frame construction. These walls were subjected to different exterior and interior conditions and varying initial moisture content of OSB sheathing board components. The present hygrothermal model was recently developed at NRC-IRC. This model solves the highly nonlinear and coupled Heat, Air and Moisture (HAM) transport equations. The results showed that the overall agreements between the present model and the hygIRC-2D model as well as the experimental measurements were reasonably good in terms of the shapes of the drying and drying rate curves. Additionally, the predicted average moisture content of the different wall assemblies over the test periods were in good agreement, all being within +5% of those measured., ICBEST 2010: International Conference on Building Envelope Systems and Technologies: 27 June 2010, Vancouver, B.C.

This paper focuses on the simulation results of three exterior wall designs in the Beijing climate and how these particular results have been incorporated into guidelines for construction design and on-site building practices in that region of China. The simulation tool is hygIRC-2D. Simulations are conducted assuming (1) vapour diffusion without air leakage, (2) vapour diffusion with various levels of air leakage, (3) rain screens or no rain screens, (4) vapour retarding or normal latex paint over the drywall; and (5) typical interior climatic conditions. The simulation results are processed to provide a variety of graphical information including the RHT index (moisture response indicator) and moisture content readings in wood structural members (upper and lower plates) and wood structural sheathing. Simulation results and subsequent analyses provide guidance on the relative performances and suitability of these assemblies for wood frame construction in the Beijing region and other areas of China with similar climates.

This paper presents the construction features of the fibre-powder composite and its thermal properties. The scopes of future investigation on the fibre-powder composite to be used in the construction of vacuum insulation panel have also been identified., 9th International Vacuum Insulation Symposium: 17 September 2009, London, UK

The performance of a building envelope component is usually assessed based on the moisture analysis of individual components (such as cladding, sheathing board and/or drywall) for their drying potentials and likelihood of occurrence of problems associated with high moisture accumulation. In the current building envelope simulation practice, the indoor and outdoor boundary conditions are predefined in the context of the local weather data. The indoor boundary conditions are usually assumed to be constant throughout the simulation period, or two sets of values for the summer and winter periods are assumed. Although the outdoor boundary condition (weather data) is independent of the hygrothermal condition of the envelope, the indoor condition is highly influenced by the building enclosure and occupants' activities. Consequently, simplistic assumptions of indoor humidity profiles, which ignore the dynamic coupling of the indoor environment and building enclosure and represented with a set of empirical values, may lead to inaccurate conclusion about the moisture performance of the building enclosure. In this paper, the effects of indoor humidity profiles that are assumed during moisture performance evaluation of exterior building envelope component are analyzed. The indoor humidity profiles, which are considered in the study, are based on measured and simulated data of a real house. Indoor humidity models including a whole building hygrothermal model are used to generate four indoor humidity profiles. The hygrothermal dynamic responses of the building envelope component with respect to the various cases of indoor humidity assumptions are simulated and analyzed. The simulation results suggest that it is important to have more accurate indoor boundary conditions data, which are based on measurement or whole building hygrothermal modelling, to satisfactorily asses the moisture performance of a building enclosure and potential occupants health problems related to mould growth., The Fourth International Building Physics Conference: Energy Efficiency and New Approaches: 15 June 2009, Istanbul, Turkey

In Canada wood frame exterior building envelope construction is widely used. However, this type of building envelope construction is not traditionally used in Taiwan. This paper presents result from a research project that investigated the hygrothermal (i.e. moisture and thermal) performance of the wood frame exterior building envelope construction practices in Taichung (Taiwan). This has been done using a two-dimensional hygrothermal simulation tool. The first series of simulations was conducted for exterior building envelope constructions that had no air leakage. Thereafter, selected simulations were also conducted with air leakage through the exterior building envelope. The outputs from the simulations have been analyzed with the help of a moisture response indicator called RHT index. Simulation results indicate the relative performances and suitability of different types wood frame building envelope constructions in Taichung (Taiwan)., Aussi disponible en français: L'application d'outils de simulation pour estimer la réponse hygrothermique d'enveloppes à ossature de bois à Taïwan, 12th Conference on Building Science and Technology: 7 May 2009, Montreal, QC

This paper describes the use of a whole building hygrothermal model (HAMFitPlus) to analyze the energy savings resulting from three programmable thermostat setting schemes in a real occupied residential house. It discusses the effect of these schemes on the indoor relative humidity and moisture performance. In the first thermostat-setting scheme, the indoor temperature is maintained constant at 21 at all time (no set-back). In the second thermostat-setting scheme, the indoor temperature is maintained at 21ºC from 7:00 to 21:00 h, and then setback to 17ºC for the remaining hours (21:00 to 7:00 h)., Building Physics Symposium, October 29, 2008, Leuven, Belgium

The thermal insulating efficiency of closed-cell foam insulation with a captive blowing agent changes over time during its service life in building envelope construction. Hence, the long-term thermal resistance (LTTR) value of closed-cell foam insulation has a great significance to the building envelope designers. Researchers at the National Research Council Canada Institute for Research in Construction (NRC-IRC) have worked on various aspects of aging characteristics of closed-cell foam insulation during the past two decades. This paper will provide a comprehensive scientific outline of the research activities that have been carried out at the NRC-IRC on the aging of closed-cell foam insulation and its practical implications on the North American construction industry., Third Global Insulation Conference and Exhibition: 16 October 2008, Barcelona, Spain

This paper presents some results of a research project that investigated the hygrothermal performance of the Canadian wood-frame exterior building envelope construction practices in Shanghai and Beijing (China) and Taichung (Taiwan). The study used a two-dimensional hygrothermal simulation tool, hygIRC-2D. Four exterior walls and two roof constructions were exposed to Shanghai climatic conditions. Simulations were conducted on walls that had no air leakage and various levels of air leakage. The outputs from the simulations were analyzed with the help of a moisture response indicator called RHT index. Results indicate the relative performances and suitability of the different wall and roof assemblies in Shanghai., 8th Nordic Symposium on Building Physics, June 15, 2008, Copenhagen

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., The 11th International Conference on Durability of Building Materials and Components: 11 May 2008, Istanbul, Turkey

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., Proceedings of Thermal Performance of the Exterior Envelopes of Whole Buildings X, 2 December 2007, Clearwater, Florida

Water vapor transmission properties of building materials play an important role in the overall moisture management and durability of the exterior building envelopes. The cup method, as described in the ASTM Standard Test Methods for Water Vapor Transmission of Materials (E 96), is widely used in North America and other parts of the world for this purpose. Recently the latest ASTM standard (E 96/E 96M ? 05) has started taking into account various corrections (e.g. buoyancy correction, correction for resistance due to still air and specimen surface, edge mask correction etc.) while analyzing the results obtained from the cup methods. This paper presents the results obtained from the laboratory tests carried out on more than fifty building materials. These results have been used to demonstrate the significance of various corrections on the measured water vapor permeability or permeance of various commonly used building materials or components. The results presented in this paper were discussed in the ASTM technical task group to underline the importance of various corrections for the calculation of water vapor transmission properties of various building materials.

The focus of this study was to examine the reliability of models that are available in the open literature for simulating the interior moisture conditions, comparing the predicted interior relative humidity to measured data. Four models, for predicting the indoor relative humidity in houses were tested against measured relative humidity data for 25 houses.The models considered were primarily developed as design tools.

On-going discussions on various forms of moisture transport in buildings have often focused on the nature of vapour diffusion in wall assemblies. Recent field investigations at the Institute for Research in Construction (IRC), NRC Canada, have yielded data on the effect of solar radiation on the exterior surface temperature of wall assemblies. On a sunny day in August 2004, on the exterior surface of a south-facing wall, a temperature rise close to 25°C over the surrounding air temperature was recorded. Coincident increases in the absolute humidity ratio of the air in the cavity behind the brick were measured, suggesting inward drive of brick moisture into that cavity. A laboratory facility at IRC, called the Envelope Environmental Exposure Facility (EEEF) has been used to launch an investigation on the behaviour of the vapour diffusion in exterior walls exposed to solar radiation. A 2.4 m by 2.4 m test specimen of a simple wallassembly was constructed, the exterior surface of the specimen soaked in simulated rain conditions and subsequently heated by infrared heaters to mimic the rise in surface temperature due to solar radiation. The wall was fully instrumented for temperature and relative humidity measurements at both surfaces as well as at every interface. This paper presents a brief description of the EEEF, details of the test specimen and data collection, and data from the above experiment. A clear indication of an inward diffusion of water vapour across the wall as the exterior surface is heated is derived from both laboratory controlled and field experiments, 11th Canadian Building Science and Technology Conference, 22 March 2007, Banff, Alberta

Recent computer simulation studies at the Institute for Research in Construction (IRC) of the National Research Council (NRC) Canada have indicated that the combined wetting and drying potential of the wood-frame face sealed stucco clad wall is significantly influenced by the water vapour permeability and liquid diffusivity of the stucco material. Lower liquid diffusivity and higher water vapour permeability of the stucco material can positively influence the overall moisture management capacity of the wood-frame face sealed stucco clad wall. This paper presents preliminary experimental results from a pilot research project that aims to use the lessons learned from the simulation studies for the development of new materials or modify existing materials. The results from the experimental study show that it is possible to reduce the water absorption coefficient (a measure of liquid diffusivity) of the stucco material without reducing water vapour permeability through appropriate mix design., 11th Canadian Building Science and Technology Conference: 22 March 2007, Banff, Canada

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., 3rd International Building Physics Conference: 27 August 2006, Montreal, QC.

Heat, air, and moisture transfer models that are used as practical building design tools require reliable inputs to provide meaningful results. One of these inputs is the set of heat, air, and moisture transport properties of materials. For any given class of building materials the properties may vary within a broad range. This paper reports the porosity, density, matrix density, thermal conductivity, equilibrium moisture content, water vapor permeability, water absorption coefficient, liquid diffusivity, and air permeability of regular lime stucco, regular Portland cement stucco, and acrylic stucco that are commonly used in North America. The experimental and analytical procedures follow either international standards or well-established methodologies.

Moisture management in the building envelope plays an important role determining long-term durability and serviceability of Canadian houses. Improper or inadequate moisture management has caused severe damages in the Canadian houses. In many cases, building materials may not be able to compensate for deficiencies in the wall design and construction. Service life, as a result of these deficiencies, is shortened in the areas of heavy and sustained rainfall. In such a situation, it is important to develop a proper understanding of the mechanisms of moisture transport into and out of the building envelope, address the deficiencies, incorporate design features that will reduce moisture loading on the wall, and consider the modification of the hygrothermal properties of the building materials. In the latter case, such modifications of the hygrothermal properties of the building material can be engineered through innovative manufacturing technique and the material evolved through the process can lead to better moisture management in the building envelope., Le contrôle de l'humidité dans l'enveloppe de bâtiment joue un rôle important dans la détermination de la durabilité et de la tenue en service à long terme des maisons canadiennes. Au Canada, le contrôle de l'humidité insuffisant ou inadéquat a dans le passé causé d'importants dommages à des maisons. Dans de nombreux cas, les matériaux de construction pouvaient ne pas être capables de compenser les manques dans la conception et la construction des murs. La durée de vie utile, en conséquence de tels manques ou déficiences, se trouve raccourcie dans les régions à pluviosité forte ou soutenue. En pareille situation, il est important de développer une juste compréhension des mécanismes de la migration de l'humidité dans l'enveloppe du bâtiment et hors de celle-ci, de corriger ces manques ou déficiences, d'incorporer des caractéristiques de conception qui réduiront la charge d'humidité sur le mur et d'envisager la modification des propriétés hygrothermiques des matériaux de construction.

An ASHRAE Research Project (RP-1018) that has been concluded at the Institute for Research in Construction, the National Research Council of Canada, has resulted in a unique database on many hygrothermal properties of many common building and insulation materials that are currently used in North America. The properties that are determined include thermal conductivity, equilibrium moisture content, water vapor transmission characteristics, water absorption coefficient, moisture diffusivity and airflow characteristics. The experimental and analytical procedures used in the research project are all based on either International Standards or on well-documented and peer-reviewed approaches. The materials that have been investigated in the project include: several wood-based products, such as oriented strand board, plywood, wood fiberboard and composite wood siding; masonry products, such as clay brick, mortar and aerated concrete; five species of lumber; cladding products, such as stucco, fiber cement board and the exterior coatings of EIFS systems; seven insulation products; six sheathing membranes; interior gypsum board, primer and a latex paint; a natural stone, a cement-based sheathing board and vinyl wallpaper. This paper lists the basic information on all materials that are investigated. It also summarizes the principles of the experimental procedures. Illustrative examples of the information that have been generated in the research project are presented. Results from statistical analyses are highlighted.

Building membranes are integral parts of North American Buildings. Some are installed beneath commonly used exterior claddings, brick and stucco to reduce the risk of water infiltration into the wall systems. Others are used for controlling vapor diffusion though the envelope or as the airtight element of the air barrier system of the envelope. To determine the suitability of a membrane for its intended application, it is necessary to have reliable information on its inherent physical properties. This paper reports the water vapor permeance, the air permeance, and the water absorption coefficient for 18 building membranes that are found in North American markets today. These membranes include paper-based as well as polymer-based materials. The properties reported here show that at the design stage most of the membranes can be considered as the airtight element of air barrier systems and as part of the second line of defense against rainwater penetration. The membranes provide a range of values for water vapor permeance and therefore open up opportunities for a designer to integrate innovative vapor diffusion control strategies for exterior walls and to prolong their service lives.

This paper describes a 'modified cup method' and its application to investigate the effects of temperature on the water vapor transmission properties of building materials. 'Modified cup method' is a simple and versatile technique that allows the user to vary the temperature condition of the test without altering the relative humidity. Two commonly-used building materials considered in this study were fiberboard, and gypsum board. The five temperature levels under consideration were between 7°C and 43°C. The water vapor transmission properties were measured at 50 % average relative humidity. The results obtained from these tests are critically analyzed and reported in this paper. These results demonstrate that there is a steady exponential increase of water vapor transmission (WVT) rate, through both the materials tested, with temperature. However, water vapor permeability (WVP) through the materials shows no significant change due to the variation of temperature between 7 and 43°C. The general observations made in this study confirm that the 'modified cup method' could be used reliably to measure water vapor transmission properties of building materials. Detailed analysis of the test results also reaffirm the fact that, for fiberboard and gypsum board, at 50 % average relative humidity condition, the water vapor permeability is not dependent on the temperature condition.

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., 7th Symposium on Building Physics in the Nordic Countries, June 13, 2005, Reykjavik, Iceland

Efficient insulating systems are the key to the energy efficiency of a building envelope. Vacuum Insulation Panels (VIPs) offer excellent thermal resistance properties that can enhance the energy efficiency of insulating systems, use less space, and provide savings in energy consumption. However, from a Canadian perspective, VIP systems are little known and indeed unused in the building industry. There is a need to investigate the prospect of using VIPs in various components of building envelope. The long-term thermal insulating efficiency of the VIPs depends on its ability to maintain an adequate level of vacuum inside the panel. For design purpose the long-term thermal insulating characteristics of the VIPs needs to be understood and defined. This paper addresses some of the test methods that could accelerate the long term changes in thermal resistance and presents selected results from tests using elevated pressure, relative humidity and temperature on three types of VIPs., 10th Canadian Conference on Building Science and Technology, May 12, 2005, Ottawa, Canada

Closed-cell polyisocyanurate (polyiso) foam insulation with gas barriers or impermeable facers is used in various building envelope applications. The impermeable gas barrier on both sides of polyiso foam insulation board is designed to maintain the long-term thermal resistance (LTTR) of the insulation at a higher level. Recently, researchers at the Institute for Research in Construction (IRC) / National Research Council (NRC) of Canada, in association with the Canadian Polyisocyanurate Council, have been working to develop a standard test methodology that would help to quantify the design LTTR value of polyiso foam insulation boards with impermeable facers. This paper presents selected results from laboratory tests, field observations and numerical modeling. Comparisons among these results indicate that the extent of thermal aging of impermeably faced polyiso foam boards can vary in different products. A concept of combined lateral and normal diffusion has been introduced in the numerical modeling to help prediction of the long-term thermal behavior of impermeably faced polyiso products. However, comparisons between the experimental and numerical modeling results indicate that the ratio of lateral to normal (L/N) diffusion rate is not the same for full thickness boards as for thin slices., IX International Conference on Performance of Exterior Envelopes of Whole Buildings: 05 December 2004, Clearwater Beach, Florida

Aussi disponible en français: Nouveau projet international pour caractériser l'effet des flux d'air, de chaleur et d'humidité sur la performance globale des bâtiments

Also available in English: New international project to study whole-building heat, air and moisture flows

This paper investigates the role of the vapour barrier in a wood-frame stucco wall with the help of two dimensional hygrothermal simulation tool, hygIRC-2D, developed at the Institute for Research inConstruction of the National Research Council Canada. For this purpose, the wall is subjected to theexterior weather conditions of Vancouver, Canada. Three different interior climatic conditions and sevendifferent vapour diffusion strategies, generated by varying the water vapour permeance of the vapourbarrier, installed outboard of the interior finish, have been considered in this study. The outputs from the simulations have been analysed with the help of a novel moisture response indicator called RHT index. Simulation results indicate that the vapour permeance characteristics of the vapour barrier, in terms of water vapour permeance, plays a very important role in the overall moisture response of the wood-frame stucco wall. A very high or low vapour permeance of the vapour barrier does not produce the optimum moisture management strategy for the wood-frame stucco wall subjected to a climate as exists in Vancouver, Canada. Moreover, simulation results indicate that the removal of vapour barrier from the wall system can result in a heightened moisture response and a considerable accumulation of moisture in the interior gypsum board that may lead to severe consequences in particular, the premature deterioration of the interior facing board. It has also been observed from the simulation outputs that the optimum vapour diffusion strategy, that of limiting the vapour permeance of the vapour barrier, is not a function of interior climatic conditions considered in this study. It is hoped that the results reported in this paper will shed some light on a number of concerns raised in recent years on the role of vapour barrier in wood-frame stucco wall construction., CIB World Building Congress 2004: 02 May 2004, Toronto, Ontario

As the stock of buildings in Canada ages, it is expected that there will be an increase in building envelope rehabilitation work. Such activities represent an ideal opportunity to add insulation and reduce air leakage to improve energy efficiency and building envelope durability. However, there is very little information available on how to assess the moisture and thermal (i.e. energy) performance of retrofitted building envelope assemblies and select the optimum retrofit options that will maximize the energy efficiency without compromising the long-term moisture performance of the retrofitted building envelopes. This paper depicts selected results from a study that has used a two-dimensional hygrothermal simulation tool, hygIRC-2D, to assess thermal and moisture performance of retrofitted masonry walls used in high-rise construction. The performance analyses of three basic (i.e. base case) masonry wall systems (Brick Veneer - Steel Stud, Brick Veneer - Concrete Masonry, and Precast Concrete Panels - Steel Stud) with four retrofit options, located in the National Capital Region (Ottawa-Gatineau) of Canada, are presented in this paper. The results from the simulations indicate that hygrothermal simulation tools can be used to evaluate the thermal and moisture performance of various wall systems and associated retrofit options. Simulations results also indicate that with specific retrofit options the energy performance of the wall system can be improved significantly without compromising the moisture response of the wall by adding insulation and reducing air-leakage in the wall assembly. However, heat or energy loss through the wall system is directly proportional to the air-leakage characteristics of the wall system. In general, based on the results presented in this paper, it can be concluded that use of a hygrothermal simulation tool can help to identify potentially problematic retrofit strategies while more promising measures can be advanced for additional assessment through full-scale laboratory testing or field demonstration., CIB World Building Congress 2004: 02 May 2004, Toronto, Ontario

Many samples of commercially available vacuum insulation panels were tested in the laboratory to determine their physical properties such as thermal resistance, water vapour permeance of the foils and sorption characteristics of the core material. The effect of various exposure conditions, which includes 32 ºC, relative humidity up to 90 % and 5 bar over-pressure, on the thermal resistance was determined. Also, the edge effects when panels were put side by side were evaluated. The performance of the sealing foils and seams in the manufactured products was checked in terms of water vapour permeance and air permeance. The tested products seem to with stand major environmental loads. High humidity, higher temperature and even higher pressure have not significantly changed their thermal resistances in two years. Air permeance across the foils is immeasurably low. Water vapour does permeate, albeit at a very low rate(1 to 3 ng m-2 s-1 Pa-1), across the foils and seams. However, precipitated silica as a core material has appreciable capacity to adsorb and store water molecules. Though the central portions of the panels show remarkable thermal resistances, the edge effect for the same reason is significant. The joining point of the four corners of four high performance panels is only as efficient as a high performance cellular plastic insulation., The Joint NSC-NRC Workshop on Construction Technologies: 26 April 2004, Taipei, Taiwan

Aussi disponible en français: Les résultats d'une étude sur les propriétés des matériaux sont maintenant disponibles

Uncontrolled moisture accumulation in the building envelope reduces the structural integrity of components through mechanical, chemical and biological degradation. Damage induced by moisture includes rotting of wood studs and other wood-based products, efflorescence and spalling of masonry systems, and rusting of wall fasteners. Also, excessive moisture in the envelope may affect the health of occupants by providing favourable conditions for harmful organisms. For building occupants, building become "unfit-for-use" due to either questionable structural integrity of the envelope or to unhealthy indoor environment. In addition, moisture can adversely affect non-health and safety performance factors such as the effectiveness of thermal insulation and aesthetic appearance., Aussi disponible en français: Une méthode intégrée pour élaborer des stratégies de gestion de l'humidité dans les murs extérieurs, BSI 2003 of the Seminar, 1 October 2003, 15 Locations in Canada

Aussi disponible en français: hygIRC aide les concepteurs à choisir les meilleurs éléments et systèmes pour l'enveloppe du bâtiment

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., The 2nd International Conference on Research in Building Physics, 14 September 2003, Leuven, Belgium

European Community Project HAMSTAD Technology Implementation Plan: Also published in Journal of Thermal Envelope and Building Science as title "Interlaboratory Comparison of Hygric Properties of Porous Building Materials", v. 27, no. 4, April 2004, pp. 307-324.

European Community Project HAMSTAD Technology Implementation Plan: Also published in Journal of Thermal Envelope and Building Science, v. 27, no. 4, April 2004, pp. 277-305

European Community Project HAMSTAD Technology Implementation Plan: Also published in Journal of Thermal Envelope and Building Science, v. 27, no. 4, April 2004, pp. 261-276.

This paper demonstrates the application of an advanced hygrothermal modelling tool for the moisture management design of the exterior building envelope. The exterior wall system considered in this study is a wood-frame stucco wall. The hygrothermal modelling tool used for this purpose is called hygIRC. The moisture management performance of the wall assembly is assessed at two Canadian geographic locations (Ottawa and Vancouver). The moisture response of the wood-frame stucco wall is analysed using a novel moisture response indicator called RHT index. The results from this study indicate that optimum vapour diffusion strategy in a wood-frame stucco wall can be determined if well defined input parameters such as construction details, material properties and boundary conditions are available., XXX IAHS 31, World Congress on Housing, Housing Process & Product, June 23,2003, Montreal, Quebec, Canada

Sixth Japan-Canada Housing R&D Workshop Edition, 4 June 2003, Tsukuba, Japan

This document is one of the major outcomes from the consortium project called MEWS (Moisture Management in Exterior Wall Systems), carried out at the Institute for Research in Construction (IRC) of National Research Council (NRC), Canada. This report deals with the parametric analyses of four different types of wall assemblies in a building envelope. The four types of walls considered are (1) Stucco walls, (2) EIFS walls, (3) Masonry walls, and (4) Siding walls. The parametric analysis was done using IRC's hygrothermal modelling tool hygIRC. hygIRC is a 2-dimensional numerical modelling tool specifically developed for research purposes and it is continuously evolving at the IRC/NRC. The utility and reliability of hygIRC outputs have been established through laboratory measurements and benchmarking exercises., Ce document constitue l'un des principaux résultats du projet du consortium sur le contrôle de l'humidité dans les murs extérieurs (CHME) mené à l'Institut de recherche en construction (IRC) du Conseil national de recherches du Canada (CNRC). Ce rapport traite de l'analyse paramétrique de quatre types de murs intégrés à l'enveloppe d'un bâtiment: 1) murs à revêtement de stuc; 2) murs SIFE; 3) murs en maçonnerie et 4) murs à parement. L'analyse paramétrique a été réalisée à l'aide d'un programme de modélisation hygrothermique élaboré à l'IRC et nommé hygIRC. Le programme hygIRC est un outil de modélisation numérique bidimensionnelle conçu spécialement à des fins de recherche et faisant l'objet d'améliorations constantes par l'IRC et le CNRC. L'utilité et la fiabilité des données de sortie de hygIRC ont été établies au moyen de mesures en laboratoire et d'exercices d'évaluation des performances.

By 1997, several field surveys in North America had indicated that rain penetration in exterior walls and poor construction detailing contributed to the shortening of the service life of recently built exterior walls of low-rise buildings in climates with high exterior moisture loads. There was a movement in industry to rethink the ways that exterior walls had been put together in recent years, as well as a renewed appreciation that exterior climates vary in severity from one location to another. In 1998, IRC/NRC initiated a research consortium with industry partners to develop guidelines for moisture management for exterior wall systems (MEWS) in low-rise residential buildings of North America. Partners represented the wood industry, manufacturers of cladding systems, insulation materials and water resistive barriers as well as building owners and managers. The project was broken down into several tasks, from a review of literature on current construction practice to experimental work in the laboratory and mathematical modelling. The following four types of cladding systems were included in the project: Portland cement plaster (stucco), Exterior Insulation and Finish Systems (EIFS), masonry and siding, over wood-frame construction.This TG8 report is a research document. The objectives of the report are three-fold: to describe the research approach in some detail (chapter 1), to summarize its application to the four types of wall assemblies (chapters 2 - 5) and to draw general conclusions (chapter 6), based on the observations in chapters 2 - 5. The reader is strongly advised to consult the research team before the information presented in this report is used for building design considerations.

Recent research in the field of assessment of hygrothermal response has focused on either laboratory experimentation or modelling, but less work has been reported in which both aspects are combined. Indeed, it is generally acknowledged that assessing the hygrothermal performance of building envelope systems is both expensive and time consuming. Such type of studies can potentially offer useful information regarding the benchmarking of models and related methods to assess hygrothermal performance of wall assemblies. This paper focuses on the use of an advanced hygrothermal model to assess the hygrothermal response of various components in wood frame wall assemblies when subjected to nominally steady-state environmental conditions. A comparison is made of results obtained from the computer model simulations to those derived from tests on mid scale specimens in controlled laboratory measurements. The experimental results were subsequently used to help benchmark the model. Specifically, hygIRC was implemented, in this series of simulations, to assess the drying rate of various combinations of sheathing membrane in close contact with wood-based sheathing. The overall agreement between experimental and simulated results is very good in terms of the shape of the drying curve and the time taken to reach equilibrium moisture content., eSim 2002 Proceedings: 12 September 2002, University of Concordia, Montreal

This report summarizes the findings of MEWS Task Group 3 on the Properties of the following building materials. 1. Oriented Strand Board 2. Plywood 3. Brick 4. Mortar 5. Stucco 6. Wood fibreboard 7. Composite wood siding 8. Water resistive barrier 9. Exterior grade gypsum board 10. EIFS base and finish coats and 11. Spray polyurethane foam The properties that have been experimentally determined include: 1. Thermal conductivity of the dry material as a function of temperature 2. Water vapour permeability/permeance as a function of relative humidity 3. Equilibrium moisture content as a function of relative humidity/suction 4. Moisture diffusivity as function of moisture content 5. Water absorption coefficient 6. Air permeability/permeance For the first eight materials, several products were tested to establish the range of properties shown by each material available in North American market. The main purpose of this investigation was to provide representative material properties as inputs for IRC's hygrothermal model hygIRC.

Recent research in the field of assessment of hygrothermal response has focused on either laboratory experimentation or hygrothermal modelling, but less work has been reported in which both aspects are combined. Such type of studies can potentially offer useful information regarding the benchmarking of models and related methods to assess hygrothermal performance of wall assemblies. This paper briefly presents an advanced hygrothermal computer model called hygIRC. The paper also reports the results of a series of experiments in which the drying rates of oriented strand board alone or in combination with several sheathing membranes were systematically measured. Results from these experiments are compared with those derived from hygIRC simulations and subsequently used to help benchmark the model. Preliminary results on the shape of the drying curves and the time taken to establish equilibrium moisture content show good agreement between the experiments and simulation. This was one of several steps undertaken in a broader benchmarking exercise to validate the model and its implementation., Proceedings of the 12th International Heat Transfer Conference: 18 August 2002, Grenoble, France

The objective of this report is to communicate, in a very concise form, some of the accomplishments of the MEWS (Moisture Management for Exterior Wall Systems) project. This will be done in terms of the research methodology adopted, as well as the outcome of its application to the first type of walls analysed in the project - Stucco-clad exterior wood-frame wall assemblies. Only a few examples will be cited in this report. Many reports have been produced detailing the process followed and the results obtained. The interested reader is welcome to refer to these documents for a more detailed investigation of any selected topics.

An analytical approach to quantify and assess the effect of building envelope retrofit strategies on the long-term hygrothermal performance of masonry wall assemblies in high-rise buildings is presented in this paper. This approach has resulted from an on-going research project that has the main objective to predicteffects of adding supplementary insulation and air-sealing retrofit options on several types of wall assemblies, used in both commercial and residential high-rise buildings throughout different geographical locations in the country (Canada). A set of three hygrothermal indicators are defined and used to compare between the relative moisture performance of different retrofit strategies. These hygrothermalindicators predict the degree and potential for moisture related damage due to frost, chemical or biochemical attacks as well as efflorescence-subflorescence and swelling of the masonry envelope components. The impact of indoor environment and type of ventilation, the outdoor weather are also addressed by using thesehygrothermal indicators., 11th Symposium for Building Physics: 26 September 2002, Dresden, Germany

Task 4 - Environmental Conditions consisted of two main objectives: the first objective was to provide input for the parametric simulation phase of Task 7- Hygrothermal Analysis and the rain penetration test portion of Task 6 - System Performance; the second objective was to develop a method for classifying for US and Canadian climates with respect to moisture loading. Hourly weather data for approximately 400 Canadian and US locations were collected. The data spans 30 or more years. A list of 40 candidate cities was created from the locations available. Data for the 40 cities, 27 American and 13 Canadian, were analyzed and converted into the appropriate format for the Advanced Hygrothermal Model (AHM). A method for calculating a moisture index based on two independent indices, the wetting index and the drying index was developed characterize the locations in the 40 city set. From the candidate list five cities were selected: Wilmington NC, Seattle WA, Ottawa ON, Winnipeg MB, and Phoenix AZ for detailed analysis. Reference years to be input to the AHM as part of the parametric study were determined for each of the five cities selected for detailed analysis. A modified method for calculating the moisture index cities was used to select reference years. The modified method included the effect of wind-driven rain and the effect of orientation. For selecting reference years the definition of the wetting index included the direction of predominantrainfall. A wet year, a dry year, and an average year were defined as reference years for each of the five selected cities. Finally, five methods of calculating wind driven rain were reviewed and found to be ingeneral agreement. Experimental results confirm the validity of the methods reviewed. Straube's method for calculating the amount of wind driven rain impinging on a wall was selected for use. It was chosen because it is generally the most conservative of the methods considered and was also the method selected for incorporation into the AHM. Two spray rates, 100 L/m 2 -h (1.7 L/min-m 2 ) and 200 L/m 2 -h (3.4 L/min-m 2 ) and a maximum pressure level of 700 Pa +/- 300 Pa cycled at 0.5 Hz were determined from the literature and climate data. These recommendations were used in the rain penetration portion of Task 6. The second objective was to develop a method for classifying climates with respect to moisture loading. Climates were classified using a similar method used to classify the 40 candidate cities. Climates were classified according to their potential for moisture loading. Five groups were defined: Zone 1, Zone 2, Zone 3, Zone 4, and Zone 5. A provisional contour map showing isopotentials for Canada and the United States was created.

In a composite wall, each constituent component plays a specific role in effective moisture management. The moisture movement to and from the wall assembly, subjected to climatic forces, such as relative humidity (RH), temperature, rainfall and solar radiation, is influenced by the basic hygrothermal properties of the component materials. Studies conducted at the National Research Council (NRC) Canada, over the years, show that the hygrothermal properties of materials vary over a wide range. Quite naturally, such variation may influence the overall moisture response of the wall. This paper investigates the extent to which each component of the wall can influence the overall drying and wetting characteristics of an ideal (i.e., without any deficiency) wood-frame stucco wall when it is exposed to weather conditions typical of coastal Western Canada. The component materials selected include stucco, sheathing board, a sheathing membrane and a vapour barrier. Hygrothermal material properties compiled in the laboratory at the NRC and the hygrothermal modelling tool, hygIRC, developed by the NRC, are used for this purpose. The findings of this study indicate that, with further work and analysis, practical guidance could be developed to assist designers and engineers to identify the critical components and properties of the stucco wall assembly to achieve a desirable moisture management strategy for the building envelope., 6th Symposium on Building Physics in the Nordic Countries: 17 June 2002, Trondheim, Norway