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A building shall be classified as high performance building if it is energy efficient and durable and at the same time provides comfortable and healthy indoor environment for occupants. To achieve this objective, the hygrothermal performance of alternative building designs should be evaluated based on the simultaneous analysis of these three functional requirements rather than separately. In this article, a Whole-Building Hygrothermal model is used for evaluation of various retrofit design parameters that potentially enhance the overall performance of an existing residential house. The retrofit options considered in this study include changes to the reference house’s ventilation rate and operation, windows, insulation level, and various combinations of these options. Energy efficiency, building envelope and moisture management potential, indoor humidity control, and window condensation potentials are considered to be the four performance indicators in searching for a retrofit option that delivers an optimal performance. The hygrothermal simulation results indicate that changing a design parameter to improve one of the design goals may result in less optimal results in the other one or both goals, or even in some cases result in severe negative consequences.

Water absorption coefficient of a material governs the liquid moisture movement into it. In the case of various components of a building envelope, in particular exterior claddings, this is one of the most important hygrothermal material properties that needs to be assessed to determine the overall moisture management strategy. In different geographical locations, components of the building envelope, in particular the surface of the exterior cladding, are exposed to various temperature regimes. However, the effect of various temperature regimes on the water absorption coefficient of common building materials has not been adequately investigated. This study looks at the water absorption characteristic, determined through water absorption test, of three commonly used building materials (i.e., eastern white pine, red clay brick and concrete)at four temperature levels at the surface of the material, ranging from 3 to 35° C. A clear surface temperature effect on water absorption coefficient and derived liquid diffusivity value is shown in eastern white pine whereas changing the surface temperature shows no effect on the water absorption characteristic of red clay brick and concrete.

When computer models are used for predicting field performance of moist insulation products, we must learn how to quantify the variability in measured properties. This is an issue of adequate material characterization. A description by the EPS type is not sufficient. By using additional elements of material characterization such as specimen density, one improves the precision of measurements of physical properties. In the case of thermal properties, a second element of material characterization, namely the coefficient describing attenuation of thermal radiation in the material (specific extinction coefficient) is also needed. In effect, variation in thermal properties of EPS products is fully accounted for when defining only a few parameters such as bulk density, specific extinction coefficient, and thickness and temperature of the specimen.

When durability of EIFS-clad houses located in some coastal ar eas with high moisture exposure was questioned, the EIFS industry introduced new solutions. Most of the newly developed EIFS products are based on the prem ise that a weather resistant, continuous, exterior skin can be difficult to achieve, let alone maintain, during the service life of a building. These new systems have two identifiable features: (1) EIFS cladding and (2) a multifunctional second-line of de fense to contain and manage water that passed the cladding. Three subsystems and systems, namely, source drained (SD-EIFS), drained screen (DS-EIFS), and vented screen (VS-EIFS), rely on water drainage from the wall assembly. The fourth multifunctional EIFS is primarily based on the storage and drying capabilities of the wall assembly. Another prerequisite of a functional wall assembly is the presence of an air barrier. Experience indicates that only the redundant wall system with multiple defense mechanisms presents the opportunity for a durable and low-maintenance building envelope.

The Canadian approach to design accepts the presence of some con struction deficiencies and calls for a multiple-line of defense Until now, such a design has been based on the qualitative assessments rooted in experience, i.e., tradition, and involved little integration with the newly emerging analytical tools, e.g., advanced hygrothermal models. The relation between the design and climatic conditions acting on a building is not well established. Research should be undertaken to clarify the rela tionship between climate and the moisture performance of a given wall assembly, i.e., to enhance the predictability of moisture performance for different wall assemblies when constructed with some deficiencies and exposed to a given climate. To improve the correlation between climatic conditions and design practice, mois ture management of a building envelope must involve the flow-through principles. The flow-through approach is, however, much more difficult than the currently used approach with barriers. The flow-through approach requires performing computer calculations of moisture balance of all layers of the wall with regard to heat, air and moisture transport over an entire year. This is the critical element of the integrated moisture management strategy. Four papers are being written to facilitate the use of analytical tools into EIFS wall

The hygrothermal behaviour of timber frame wall is analysed using a steady-state calculation method and a two-dimensional heat, air, and moisture transport computer model. The conditions associated with exfiltration of warm and humid indoor air are examined. The physical quantities investigated included the amount of moisture accumulated in the wall cavity during the heating season and the heat loss across the wall. Several interesting correlations between moisture accumula tion in a cavity and parameters such as leakage rate, vapour permeance characteristics of the exterior boundary, additional thermal resistance offered by an exterior sheath ing, and indoor humidity level emerge. These correlations show the advantage of us ing the analytical methods in deriving design guidelines for building components. The results from the analysis are used to identify and quantify various parameters that govern the performance of air barrier systems.

Methodology for the evaluation of long-term thermal performance of cellular plastics is being developed under a collaboration of North American foam industry with the National Research Council of Canada. The mechanism of this col laboration includes a joint research project between the Society of Plastics Industry and the NRC Canada. To evaluate long-term thermal performance (LTTP) of cellular plastics the aging process must be accelerated. This can be done either by means of elevated tempera ture or by the use of thin layers of the foam. The first approach changes the permeability and solubility coefficients of different gases to such a degree that pre dicting the foam performance under field conditions is difficult. Only the thin layer approach is used in the SPI/NRC project, though the relation between aging of thin layers and that of full board is treated differently, depending on the foam uniformity. When unfaced foam is homogenous enough to permit a sim ple arithmetic operation, known as the scaling technique, this relation can be used to calculate foam aging for layers with different thicknesses. When, however, the cel lular structures of skin and core layers differ significantly, or the foam is provided with impermeable facers, then the scaling technique is not appropriate and the aging models (models of heat and mass transfer) must be used There is, however, a number of material characteristics needed as the input to these models, and the manner in which these material characteristics are generated decides upon the scope of application of this methodology. Therefore, much of this research relates to the methods of material characterization. This presentation outlines the main elements of methodology developed under the SPI/NRC project and highlights future research needs.

This article deals with determination of flexural strength for the pur pose of product quality assurance of expanded polystyrene (EPS) boards. Using a newly developed, inexpensive flexural strength tester (FST) and a systematic sam pling plan, flexural strength of eight experimental EPS products was evaluated. The FST was shown to yield results as precise as the standard ASTM test method. This agreement implies that sampling at specified mold locations and using the FST for in-plant testing could improve the process of quality assurance for EPS thermal in sulating boards.