Nicole Normandin

Effect of Surface Temperature on Water Absorption Coefficient of Building Materials

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.

Correlation Between Water Vapor and Air Permeability of Building Materials: Experimental Observations

Two fundamental properties of building materials that influence the hygrothermal performance of building envelope systems are water vapor permeability and air permeability. The driving forces for water vapor and air transmission through building materials are, respectively, partial water vapor pressure and total air pressure differentials. The theoretical similarity of the driving forces would suggest the possibility of a relationship between water vapor and air permeability. During past two decades, researchers at the National Research Council of Canada—Institute for Research in Construction have compiled a database of measured air permeability and water vapor permeability properties of building materials commonly used in North America. This material properties database was examined to identify the degree to which air permeability and water vapor permeability of the building materials might be functionally related. The database was segregated into categories for different material types. An approximately linear relationship could, within some categories, be observed between water vapor permeability and air permeability. There were however approximately as many categories within which no relationship between the parameters was apparent as there were categories within which functional relationships between the parameters were apparent. Within categories where functional relationships were apparent, the form of the relationships generally depended on the mean relative humidity at which water vapor permeability was measured. In most cases, a definitive functional form of the relationship between water vapor permeability and air permeability could not be established.

Heat, Air, and Moisture Transport Properties of Several North American Bricks and Mortar Mixes

Hygrothermal models are emerging as practical building design tools. These models require a set of reliable inputs to provide results that are meaningful to the designers. 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 six types of bricks and four mortar mixes that are commonly used in North America. The experimental and analytical procedures follow either international standards or well-established methodologies.

Vapor Permeances, Air Permeances, and Water absorption Coefficients of Building Membranes

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.

Critical Evaluation of Existing Specifications for Polyisocyanurate (ISO) Foam Insulation Boards in Roofing Applications

In North America, more than 50 % of low slope roofing applications uses faced rigid cellular polyisocyanurate (hereafter abbreviated as ISO) board as thermal insulation. Long-term performance of a roof assembly is critically dependent on the ISO characteristics during the service period in various environmental conditions. For this reason, the ASTM C 1289-02, “Standard Specification for Rigid Cellular Polyisocyanurate Thermal Insulation Board,” outlines the physical and thermal property requirements for the ISO boards. However, these requirements are based on the available knowledge, information, and consensus at the time of drafting and balloting of the ASTM standard. Nevertheless, the standard gets updated and revised when more credible data are available that solicits revisions of the current standard. This paper presents experimental results from an ongoing pilot research study that critically evaluates the ASTM C 1289-02 specification requirements for the ISO on three engineering properties: (1) dimensional stability, (2) thermal resistance, and (3) compressive strength. Preliminary results from this study reveal many unknown phenomena, particularly regarding the dimensional stability and compressive strength of ISO boards.

Calibration of a Heat Flow Meter Apparatus

A series of calibration measurements was done on a 600 mm × 600 mm heat flow meter apparatus. Several specimens of medium density glass fiber in sulation and expanded polystyrene insulation were used as transfer standards. The thickness of these transfer standards varied from 25 to 160 mm. The mean tempera ture varied from 0 to 40°C and the temperature difference across the insulation spec imens varied from 10 to 40 K. Measurements included cases in which the ambient temperature of the test assembly was either maintained within 1 K of the mean tem perature, or those with only edge insulation, and an enclosure for the whole test assembly in order to reduce the edge heat losses. A total of 91 sets of measurements were made. Each set of measurements included two sub-sets, one for the warmer(hot) plate and the other for the colder(cold) plate and each sub-set included a heat flow transducer output and the temperatures on either side of the transducer assembly. For 90 out of the 91 sets of measurements, the steady state heat flux across the specimen was correlated, with a standard deviation of 2%, to a simple linear rela tion between the average transducer output and the average of the surface tempera tures of the two transducer assemblies.

A Pressure-Volume Apparatus to Measure the Effective Thickness of Cellular Plastic Test Specimens

Thin specimens of cellular plastic insulations are used in thermal re sistance and gas diffusion property measurements. It is known that several cells on the surfaces of the test specimens are destroyed during specimen preparation. Hence the effective thickness of the test specimen differs from the geometrical thickness and proper corrections are to be made for the thickness of the destroyed surface layers before other properties are calculated.

Long-Term Thermal Performance of Impermeably Faced Polyiso Foam Boards: Field and Laboratory Observations

AbstractResearchers at the National Research Council (NRC) Canada–Construction Portfolio in association with the Canadian Polyisocyanurate Council conducted collaborative research activities on the long-term thermal resistance (LTTR) of polyisocyanurate (polyiso) foam insulation with impermeable facers. Polyiso boards are commonly used in building envelope constructions (roofs and walls) in cold regions. The primary objective of the research project was to contribute towards the development of a comprehensive test procedure that could be used to measure the LTTR of polyiso foam insulation products with impermeable facers. As a part of that initiative, a project was initiated in 2001 that consisted of accelerated aging tests using thin slices in parallel with a field investigation in which polyiso boards were installed in a purpose-built test hut at the NRC’s Ottawa campus. The polyiso boards installed in the field were monitored for a period of 6 years and subsequently removed from the test hut and tested...

Long-Term Thermal Resistance of Polyisocyanurate Foam Insulation with Impermeable Facers

Polyisocyanurate (polyiso) foam insulation with impermeable facers is known for its superior insulating properties in building envelope applications. The impermeable facer on both sides of polyiso foam insulation board is designed to increase and maintain the long-term thermal resistance (LTTR) of the insulation. Currently, the Institute for Research in Construction (IRC)/National Research Council (NRC) of Canada, in association with the Canadian Polyisocyanurate Council, has embarked on a research project 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 outlines the research project and presents preliminary test results from experimental work. These preliminary results are discussed with a view to developing a methodology that will be used as the basis for a National Standard in Canada for the determination of LTTR of polyiso foam insulation with impermeable facers.

High Performance Stucco to Optimize Moisture Management in Wood-Frame Stucco Walls

Stucco or portland cement plaster is widely used in North America as an exterior cladding material for the wood-frame walls. Recent computer-based numerical simulation studies at the National Research Council (NRC) Canada, Institute for Research in Construction (IRC) have indicated that low liquid diffusivity and high water vapor permeability of the stucco material can positively influence the overall moisture management capacity of wood-frame stucco walls. This paper presents the results from experimental and numerical modeling studies carried out at the NRC-IRC on the development of high performance stucco materials and its effect on the overall moisture management capability of wood-frame stucco walls. Liquid water and water vapor transmission properties of several commercial/conventional stucco materials and some newly formulated compositions were measured and compared under laboratory conditions. The experimental results suggest that by appropriate choice of the mix composition, addition of a proper hydrophobic admixture, and using aggregates with a hydrophobic coating, stucco material with lower liquid water diffusivity can be produced without reducing the water vapor permeability. The results from the numerical modeling study show newly developed high performance stucco materials can significantly improve the moisture management capability of wood-frame stucco walls.