scholarly journals Empirical Investigation of the Hygrothermal Diffusion Properties of Permeable Building Membranes Subjected to Variable Relative Humidity Condition

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 4053
Author(s):  
Toba Samuel Olaoye ◽  
Mark Dewsbury ◽  
Hartwig Künzel
Keyword(s):  
Relative Humidity ◽  
Empirical Investigation ◽  
Construction Material ◽  
Building Envelope ◽  
Test Method ◽  
Relative Humidity Condition ◽  
Current Test ◽  
Vapour Diffusion ◽  
Standard Tests ◽  
Diffusion Properties

Hygrothermal modelling is increasingly used to inform building envelope design. A key input for these calculations is the material’s vapour diffusion properties. Respecting a growing international concern, this research has questioned the appropriateness of the current test method to establish construction material for vapour diffusion properties. This article reports on the empirical measurement of the vapour diffusion properties of two vapour-permeable building membranes commonly used in Australia residential systems when subjected to variable relative humidity conditions. The method involved completing dry cup and wet cup standard tests as specified in ISO 12572, (23 °C and 50% relative humidity RH). Further tests were then conducted as temperature remained at 23 °C but the relative humidity changed to 35%, 65% and 80%, respectively, in order to know if the diffusion properties are the same or change with varying relative humidity. The results from the wet cup and dry cup tests under different relative humidity conditions were non-linear and different. These results indicate vapour-permeable membranes behave differently when exposed to different relative humidity conditions. In conclusion, this research demonstrates that the current vapour resistivity test method is inadequate, hence the need to establish more detailed diffusion resistivity properties in different humidity ranges that represent conditions experienced within a building’s external envelope.

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

Buildings ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 509
Author(s):  
Toba Samuel Olaoye ◽  
Mark Dewsbury ◽  
Hartwig Künzel
Keyword(s):  
Relative Humidity ◽  
Water Vapour ◽  
Construction Materials ◽  
Building Design ◽  
Building Envelope ◽  
Pressure Gradients ◽  
Moisture Management ◽  
Water Vapour Diffusion ◽  
Vapour Diffusion ◽  
Diffusion Properties

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.

Untersuchungen zum Diffusionswiderstand von Holzwerkstoffen | Diffusion resistance of timber materials

2005 ◽  
Vol 156 (3-4) ◽  
pp. 100-103
Author(s):  
Rudolf Popper ◽  
Peter Niemz ◽  
Gerhild Eberle
Keyword(s):  
Relative Humidity ◽  
Water Vapour ◽  
Middle Lamella ◽  
Solid Wood ◽  
Diffusion Resistance ◽  
Water Vapour Diffusion ◽  
Wood Panels ◽  
Vapour Diffusion ◽  
Wet Climate ◽  
Panel Thickness

The water vapour diffusion resistance of timber materials were tested in a wet climate (relative humidity ranging from 100%to 65% at 20 °C) and in a dry climate (relative humidity ranging from 0% to 65% and from 0% to 35% at 20 °c) with variation by relative humidity and vapour pressure gradient. The diffusion resistance of multilayer solid wood panels lies under or within the range of the solid wood (spruce), tending even to a lower range. This can be attributed to the loosely inserted middle lamella of the used solid wood panels, which were not correctly glued by the manufacturer. The diffusion resistance of the solid wood panels increases with decreasing moisture content and decreasing panel thickness, as well as with increasing water vapour gradient from 818 to 1520 Pa. There were clear differences between the tested timber materials. The diffusion resistance of particle composites is strongly dependent on the specific gravity. Due to laminar particles OSBs(Oriented Strand Boards) have a larger diffusion resistance than chipboards. The water vapour diffusion resistance of OSBs lies within the range of plywood.

Thermal Performance Comparison between Single and Double Storey Terrace Houses in Melaka, Malaysia

2016 ◽  
Vol 835 ◽  
pp. 416-422
Author(s):  
Fahanim Abdul Rashid ◽  
Asrul Mahjuddin Ressang Aminuddin ◽  
Norafida Ab. Ghaffar
Keyword(s):  
Relative Humidity ◽  
Thermal Comfort ◽  
Case Studies ◽  
Thermal Performance ◽  
High Energy ◽  
Performance Comparison ◽  
Building Envelope ◽  
The Difference ◽  
Economic Developments ◽  
Housing Typology

Over the past decade many studies were conducted to investigate the thermal performance of terraced houses in Malaysia. It was found that this housing typology failed to address the need for thermal comfort and alternatives to the narrow frontage with deep plan have been proposed with simulated good thermal performance. Although this is good progress for new generation of terraced houses, millions of units of terraced houses are still in use and new units with the outdated existing plans continued to get built due to consistently very high demand due to progressive urbanisation and rapid economic developments. Therefore, it is imperative that the thermal comfort issue for existing terraced houses is dealt with and through this paper a comparison between single and double storey terraced houses is made through analysis of indoor environmental monitoring (ambient temperature, relative humidity and air velocity) of two (2) selected case studies in Merlimau, Melaka. Contrary to popular belief, it is found that there is no statistical difference between both sets of indoor temperature and relative humidity between the case studies. This finding is indicative of the consistent and stable temporal temperature highs and lows in a 24 hour cycle despite the difference in indoor volume and distance between the ground floor and the roof cavity. Much of the reason is due to the materiality of the terraced houses construction and unsealed and uninsulated building envelope. Therefore, further research into improving the thermal performance of existing terraced houses of any typology have to be conducted to allow thermal comfort and to reduce reliance on high energy consuming air-conditioning.

Restrained Shrinkage Behavior of Concrete under Different Environmental Conditions

2014 ◽  
Vol 941-944 ◽  
pp. 835-841 ◽  
Author(s):  
Zhi Tao Chen ◽  
Mao Guang Li ◽  
Ying Zi Yang ◽  
Qi Liu
Keyword(s):  
Relative Humidity ◽  
Environmental Conditions ◽  
Test Method ◽  
Mineral Admixtures ◽  
Ring Test ◽  
Test Duration ◽  
Restrained Shrinkage ◽  
Shrinkage Cracking ◽  
Higher Temperature ◽  
Shrinkage Behavior

The ring test method is used to evaluate the behavior of concrete under restrained shrinkage. Four kinds of environmental conditions (20±1°C, RH60±5%; 35±1°C, RH60±5%; 50±1°C, RH15±5%; 65±1°C, RH15±5%) were designed to investigate the effect the environmental condition on the shrinkage behavior of concrete prepared with different kinds of mineral admixtures. The results show that higher temperature and lower relative humidity can increase the risk of shrinkage cracking. The addition of different mineral admixtures increases the shrinkage of concrete at room conditions. In the case of higher temperature and lower relative humidity, the addition of mineral admixtures can delay the shrinkage cracking in the test duration.

Measuring Bulk-Specific Gravity of Fine Aggregates: Development of New Test Method

2000 ◽  
Vol 1721 (1) ◽  
pp. 81-90 ◽  
Author(s):  
Prithvi S. Kandhal ◽  
Rajib B. Mallick ◽  
Mike Huner
Keyword(s):  
Specific Gravity ◽  
Asphalt Binder ◽  
Test Method ◽  
Fine Aggregate ◽  
Test Results ◽  
Rotating Drum ◽  
Current Test ◽  
Fine Aggregates ◽  
Repeatability And Reproducibility ◽  
Prototype Device

Bulk specific gravity of the fine aggregate is used in hot-mix asphalt volumetric-mix design (including Superpave) to determine the amount of asphalt binder absorbed by the aggregate and the percentage of voids in the mineral aggregate. The current test method (AASHTO T84) uses a cone method to establish the saturated surface dry (SSD) condition of the sample, which is necessary to conduct the test. This method does not work satisfactorily for fine aggregates that are very angular and have rough surface texture and, therefore, do not slump readily when in SSD condition. A research project was undertaken to develop automated equipment and a method of establishing the SSD condition of the fine aggregate. The wet sample of the fine aggregate is placed in a rotating drum and subjected to a steady flow of warm air. The temperature gradient of the incoming and outgoing air and the relative humidity of the outgoing air are monitored to establish the SSD condition. Two prototype devices were constructed. The test results obtained with the second prototype device are encouraging and are reported. Further improvements to be made to the second prototype device to improve the repeatability and reproducibility of the test have been identified.

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