•Determination of a wide range of moisture contents.•One measuring system for different building materials.•Measuring of different modifications and treatments.
The performance of porous and ...hygroscopic building materials is closely connected to its sorption properties and ability to get wet. Weight, mechanical, acoustic, and thermal properties as well as the resistance to discoloring and decay causing organisms are affected by moisture. For various reasons and purposes it is therefore recommendable to monitor the moisture content of building components continuously. The most common and most easily applicable methods are electrical resistance measurements. They can be applied to wood and wood-based materials as well as to mineral products such as mortar and brick. However, resistivity measurements require material specific characteristics and a temperature compensation since both parameters have a significant effect on electrical conductivity.
This study aimed on developing a model to determine the moisture content at any temperature for different building materials such as native and modified wood as well as untreated and hydrophobized mortar. Therefore, the electrical resistance was measured with a data logging device in the giga ohm range to obtain values at low moisture contents. The model enables measurements at a wide range of moisture contents and suited with an acceptably high accuracy by using the appropriate resistance characteristic for each building material.
The changing climate may influence building performance in several different aspects. In respect to the hygrothermal performance, excessive moisture arising from climate loads and present in wall ...assemblies over a prolonged period of time is the cause of many detrimental effects on wall components; notably, such effects may become more significant under a changing climate. The occurrence of these effects can be assessed by undertaking hygrothermal simulations. However, numerical simulations can be time-consuming, especially when evaluating the detrimental effects over a long period, which is necessary for assessing the impacts of climate change on building envelope components. A means to reduce such a time consuming and costly simulation effort is to select a set of representative years from the series of long-term climate data; a set of Moisture Reference Year (MRY), with the expectation of obtaining similar results as those obtained from the long-term simulations. This study assesses the reliability of using MRY for evaluating the long-term hygrothermal performance of wall assemblies. The MRY were selected based on moisture index (MI) rankings for historical and future climatological periods. The simulations using MRY were repeated at least 2 times and up to 10 times, with the results compared to those obtained from 31 years of consecutive simulations. Two types of wood-frame wall assemblies, each with different types of exterior cladding, were analyzed. Several criteria were selected for comparison. The results showed that the required number of repetitions of MRY is determined by the parameters used for comparisons.
•Assessed the reliability of using moisture reference years (MRYs).•Determined the required number of repetitions of MRYs under different criteria.•Moisture index was used as the criteria for the MRYs selection.•The MRYs approach is suitable for assessing changes in wood frame wall performance.
Cross-laminated timber (CLT) is a type of mass timber panel used in floor, wall, and roof assemblies. An important consideration in design and construction of timber buildings is moisture durability. ...This study characterized the hygrothermal performance of CLT panels with laboratory measurements at multiple scales, field measurements, and modeling. The CLT panels consisted of five layers, four with spruce-pine-fir lumber and one with Douglas-fir lumber. Laboratory characterization involved measurements on small specimens that included material from only one or two layers and large specimens that included all five layers of the CLT panel. Water absorption was measured with panel specimens partially immersed in water, and a new method was developed where panels were exposed to ponded water on the top surface. This configuration gave a higher rate of water uptake than the partial immersion test. The rate of drying was much slower when the wetted surface was covered with an impermeable membrane. Measured hygrothermal properties were implemented in a one-dimensional transient hygrothermal model. Simulation of water uptake indicated that vapor diffusion had a significant contribution in parallel with liquid transport. A simple approximation for liquid transport coefficients, with identical coefficients for suction and redistribution, was adequate for simulating panel-scale wetting and drying. Finally, hygrothermal simulation of a CLT roof assembly that had been monitored in a companion field study showed agreement in most cases within the sensor uncertainty. Although the hygrothermal properties are particular to the wood species and CLT panels investigated here, the modeling approach is broadly applicable.
•Moisture and thermal properties of cross-laminated timber (CLT) were measured.•New method was developed for measuring water absorption on top of CLT panel.•Vapor diffusion contributed to water uptake in parallel with liquid transport.•1-D transient hygrothermal model was validated with laboratory experiments.•Simulation of a CLT roof assembly compared well with field measurements.
•Commonly used wood panels’ bio-durability is highlighted in this research.•The results showed untreated OSB and CLT were very susceptible to biodegradation. In comparison untreated LVL panels were ...less susceptible.•Surface application of boron biocide prevented decay development.•Research highlighted the need for further research to understand the extent of moisture ingress in wooden panels.
The use of sustainably grown trees and subsequent wood products in built environment contribute towards sustainable future. With proven improved performance in fire and seismic characteristic, the projected market potential for softwood Engineered Wood Products such as CLT (Cross Laminated Timber) and LVL (Laminated Veneer Lumber) for multi-story buildings are very positive. However, potential prolonged rain leakage or moisture exposure during construction and in-service could pose considerable concern for its durability and reputation.
This research was conducted to assess the decay resistance of LVL, OSB (Oriented Strand Board) and CLT produced from radiata pine in an accelerated trial. This testing method is used in establishing the effectiveness of wood products in framing subject to intermittent wetting. The results showed untreated OSB and CLT were very susceptible to decay. In comparison, LVL was less susceptible. Testing conducted on CLT using surface application of boron preservative prevented decay. Further work is needed to understand the full extent of moisture ingress in wooden panels during construction and service of the multi-story buildings and improving the durability of panel products.
The warp-knitted fully formed products are widely popular because of their fast production speed, seamless, beautiful patterns, and wearing comfort. The structure and performance of the warp-knitted ...head mask influence the wearer's physiological and psychological state. In this article, according to the structure of the human head, a warp-knitted fully formed head mask technology model was established. Afterward, the article designed nine kinds of jacquard stitches and tested heat-moisture performance. A comprehensive evaluation system for the heat-moisture performance of jacquard stitches was installed based on a fuzzy matter-element analysis model. The all-around heat-moisture performance of nine kinds of jacquard stitches was evaluated, and the factors affecting the heat-moisture performance of jacquard stitches were analyzed. The research aims to provide a reference for the structure optimization and performance research of warp-knitted fully formed head masks.
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•The importance of wood in outdoor applications is increasing.•Durability of wood is predominantly influenced by inherent durability and wetting ability.•There is no standard ...procedure for assessment of wetting ability.•Wetting ability changes during weathering.
After the durability of wood against wood decay fungi, its water performance is the next most important factor that influences the performance of wood in outdoor, above-ground applications. It is therefore of major importance to optimize methods that are able to predict the moisture behaviour of wood in outdoor applications. In order to elucidate these questions, samples were prepared from European oak (Quercus robur/Q. petraea), sweet chestnut (Castanea sativa), European larch (Larix decidua), Scots pine heartwood and sapwood (Pinus sylvestris), Norway spruce (Picea abies) and beech (Fagus sylvatica). The moisture performance of the samples was altered by thermal modification, wax, oil and biocide treatment. Two types of specimens were prepared; smaller specimens (1.5 × 2.5 × 5.0 cm) were exposed to natural weathering for three periods (9, 18 and 27 months) and subsequently analyzed in the laboratory with various methods (contact angle, short- and long-term water uptake and water vapor uptake). In parallel, bigger specimens (2.5 × 5.0 × 50 cm) were exposed outdoors in a monolayer exposure and equipped with moisture monitoring sensors for 18 months. Water performance of wood could change as a result of weathering, being the most evident at thermally modified wood, where the decrease of the moisture performance was the most evident. The results of the study clearly showed that the water performance of the majority of the materials decreased with natural weathering. These results indicate that in order to elucidate the moisture performance of wood fully, a variety of laboratory tests needs to be applied, relating to both liquid water performance and water vapour interactions with wood.
Comprehensive approaches to predict performance of wood products are requested by international standards, and the first attempts have been made in the frame of European research projects. However, ...there is still an imminent need for a methodology to implement the durability and moisture performance of wood in an engineering design method and performance classification system. The aim of this study was therefore to establish an approach to predict service life of wood above ground taking into account the combined effect of wetting ability and durability data. A comprehensive data set was obtained from laboratory durability tests and still ongoing field trials in Norway, Germany and Sweden. In addition, four different wetting ability tests were performed with the same material. Based on a dose–response concept, decay rates for specimens exposed above ground were predicted implementing various indicating factors. A model was developed and optimised taking into account the resistance of wood against soft, white and brown rot as well as relevant types of water uptake and release. Decay rates from above-ground field tests at different test sites in Norway were predicted with the model. In a second step, the model was validated using data from laboratory and field tests performed in Germany and Sweden. The model was found to be fairly reliable, and it has the advantage to get implemented into existing engineering design guidelines. The approach at hand might furthermore be used for implementing wetting ability data into performance classification as requested by European standardisation bodies.
Basements used for habitation represent a major challenge in terms of moisture safety design; they are prone to high moisture strain and have a limited ability for outward drying compared to ...structures above grade. Exterior vapour-permeable thermal insulation is used in countries with cold climates to enable outward drying. However, its effect is not well documented when combined with a dimpled membrane. A laboratory experiment was performed to investigate the outward drying of concrete walls and to generate data for the validation of hygrothermal simulations. Two wall segments with vapour-permeable insulation and exterior dimpled membranes were compared with a segment having a dimpled membrane positioned between the concrete and exterior insulation. The segments were subjected to a steady warm interior and a cold exterior climate in a climate simulator. Weight change, precipitated condensation, and temperature data were monitored for six months. Although the weights varied nonuniformly at the start, they decreased uniformly during the last four months; they exhibited the same rate and variations of weight change. No precipitated condensation occurred in the air gaps, although the moisture content of the concrete was high and the driving potential for diffusion (temperature gradient) was large. Results indicate that the concrete's ability to transfer moisture to the drying surface limits outward drying. Hence, the vapour permeability of the insulation and the membrane position were less influential. The moisture transfer properties of concrete currently used in basements should be investigated to better predict the long-term moisture performance of products and solutions for basements.
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•The outward drying of thermally insulated basement walls was studied.•A novel experimental method for walls investigated in a climate simulator.•Load cells were used to measure drying through weight change monitoring.•Two positions of the dimpled membrane were compared.•Data for validation of hygrothermal simulations were generated.
The overall building performance depends mainly on the energy performance, indoor air quality, and moisture performance. In order to accurately calculate the building performance, the development of ...a model with the ability to integrate all three performances is required. In this research, a combination of three models namely EnergyPlus for energy, CONTAM for indoor air quality, and WUFI for moisture transport are used to develop an integrated model. The mechanism of this combination is based on the exchange of temperatures, airflows, and heating-cooling flows control variables between all three sub-models. By using the paired sample t-test, an integrated model is verified and its accuracy is validated. The accuracy of the integrated model is verified by the paired sample t-test. In order to analyze the accuracy of the integrated model in comparison with single models, four scenarios of airtight fan off, airtight fan on, leaky fan off, and leaky fan on are defined for a three-story-house subjected to three different climate cities of Montreal, Vancouver, and Miami. Percentage differences of simulated measures with the ASHRAE Standard are considered as the performance criteria. The simulated results by single and integrated models are compared and analyzed. Finally, the scenarios with the high performances are evaluated in terms of energy efficiency, indoor air quality, and moisture for Montreal, Vancouver, and Miami. Overall, it can be concluded that an integrated model should be developed.
•A model on the heat and moisture transmission in multilayer walls is proposed and validated.•The model is applied to predict the two insulation systems under the natural climate conditions.•The ...results show that the annual energy consumption of the system is about 1 kWh/m2 higher.
The thermal and moisture performance of building envelope has an important influence on the energy consumption of buildings. In order to evaluate the thermal and moisture performance of external thermal insulation composite system (ETICS) with periodic freezing and thawing, a mathematical model considering the impact of water vapor, liquid water and solid ice on the heat and moisture transmission in multilayer walls is proposed. Two experiments are designed to verify the reliability of the model by measuring heat transfer characteristics, moisture transfer characteristics and ice content. The proposed model is applied to investigate the thermal and moisture performance of two insulation systems widely used in China under the natural climate conditions of Harbin (a severe cold region) for ten years in this article. The results show that most of liquid water is concentrated in the concrete layer, and freezing-thawing and temperature drop mainly occur in the insulation layer. Water content and ice content lead to an average increase of 15.5% and 14.6% in the heat transfer coefficient of the two insulation systems compared with that of their dry state, respectively, over the ten years, which leads to the heat transfer coefficient of the system 1 to exceed the specified value in the Chinese national standard. The annual energy consumption of the insulation system with freezing-thawing is on average 1 kWh/m2 of surface area higher than that without freezing-thawing. In addition, a correction coefficient model of heat transfer coefficient is proposed. The data shows that the correction coefficient model proposed in this article is reasonable, and the correction coefficient of the initial state is more suitable than the constant for thermal design of thermal insulation systems.
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