Laboratory Measurement and Boundary Conditions for the Water Vapour Resistivity Properties of Typical Australian Impermeable and Smart Pliable Membranes

Toba Samuel Olaoye,Mark Dewsbury,Hartwig Künzel

doi:10.3390/buildings11110509

Toba Samuel Olaoye, Mark Dewsbury + Show 1 more

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https://doi.org/10.3390/buildings11110509

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Abstract

The duo of better insulated and more air-tight envelopes without appropriate consideration of water vapour diffusion and envelope moisture management has often demonstrated an increased potential of moisture accumulation, interstitial condensation, and mould growth within the building envelope. To inform a resilient, energy efficient, and healthy building design, long-term transient hygrothermal modelling are required. Since 2008, concern has been raised to the Australian building regulators regarding the need to establish the vapour diffusion properties of construction materials, in order to develop a hygrothermal regulatory framework. This paper discusses the results from laboratory testing of the vapour diffusion properties of two common reflective pliable membranes, and one smart pliable membrane. The two reflective pliable membranes are often used within the exterior walls of Australian buildings. The smart pliable membrane is a relatively new, internationally available product. The three membranes were tested as per ISO 12,572 at 23 °C and 50% RH. To establish if the vapour resistivity properties were constant, under different relative humidity conditions, the membranes were further tested at 23 °C and relative humidity values of 35%, 65%, and 80%. The results of the three pliable membranes show that the vapour resistivity properties varied in a non-linear (dynamic) manner subject to relative humidity. In conclusion, this research demonstrates that regardless of the class, each of the tested membrane types behaved differently under varying relative humidity and pressure gradients within the testing laboratory.

Highlights

The aim of this research was to investigate whether the single point vapour resistivity test method as described in ISO 12572 and ASTM E 96m provides adequate data to inform building envelope hygrothermal simulation
The current standard only requires a single point measurement for materials tested at 23 ◦ C and 50% relative humidity (RH)
This article reports on the observed water vapour resistivity properties of two impermeable pliable membranes, and one smart pliable membrane, when tested under different relative humidity conditions, in order to plot multiple point, rather than single point, hygrothermal boundary curves for each of these materials

Summary

Introduction

The aim of this research was to investigate whether the single point vapour resistivity test method as described in ISO 12572 and ASTM E 96m provides adequate data to inform building envelope hygrothermal simulation. This article reports on the observed water vapour resistivity properties of two impermeable pliable membranes, and one smart pliable membrane, when tested under different relative humidity conditions (humidity-dependent), in order to plot multiple point, rather than single point, hygrothermal boundary curves for each of these materials. In 2019, Australia’s national building regulations, the National Construction Code (NCC), included the first performance requirement regarding condensation. These regulations were the result of significant market-based concerns about the visible presence of condensation and mould prevalent in many Australian new buildings. Reflecting the universal acceptance that mould spores affect human health, the new clauses were included within the Health and Amenity section [6,7,8]

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