Water Vapor Diffusion Resistance Factor Research Articles

Performance Evaluation of Thermal Insulation Materials from Sheep's Wool and Hemp Fibres.

In the current work, the performance properties of natural-fibre-based thermal insulation materials were examined. For this purpose, three different compositions of natural fibres were prepared: pure sheep wool (SW), wool and industrial hemp (SW/HF) fibres, and pure industrial hemp (HF) fibres. Low-melt bicomponent polylactide (PLA) fibres were used as a binding material. For specimens prepared from natural fibres, the dependence of the thermal conductivity, the tensile strength along and across the direction of product formation, and the short-term water absorption on the density of the specimens and the flammability parameters were determined. In addition, to reduce the water absorption and flammability, the specimens were coated with hydrophobic agents and flame retardants. The obtained research results were also statistically processed. The analysis of the results showed that the thermal conductivity of natural-fibre-based thermal insulation materials varied within the range of 0.0333 ÷ 0.0438 W/(m·K), the tensile strength varied from 2.5 to 130 kPa, the short-term water absorption varied from 0.5 to 8.5 kg/m2, and the water vapour diffusion resistance factor varied from 2.537 to 2.667. It was additionally determined that all the studied products were flammable. The water absorption and flammability values were significantly reduced by the use of hydrophobic agents and flame retardants.

Evaluation of the Effect of the Composition of the Foam Glass Concrete on Its Flammability and Moisture Characteristics

The purpose of this study was to evaluate the moisture and flammability characteristics of lightweight concrete with different aggregates and different amounts of cement according to different criteria. The moisture properties of the specimens were evaluated by the coefficient of water absorption due to capillary action, short-term water absorption, and water vapour permeability. Short-term water absorption correlated with the density of the specimens, and capillary absorption was evaluated depending on the soaking time, amount of cement, and type of lightweight aggregate. The values of the water vapour diffusion resistance factor were estimated based on the amount of cement, the type of lightweight aggregate, the density, and the porosity. The porosity correlated with the amount of cement and the type of lightweight aggregate. The flammability properties of concrete with lightweight aggregate were evaluated by several methods, such as the single flame source test, the single burning item test, and the non-combustibility test. After assessing the flammability characteristics, a structure analysis of the samples was specifically performed to assess the processes that occur during the combustion of lightweight concrete. It was found that short-term water absorption depended mainly on the density, capillary absorption on the amount of cement, and the water vapour diffusion resistance factor, flammability, and thermal stability of lightweight concrete on the type of granules.

Stabilization effect on the hygrothermal performance of rammed earth materials

The increasing interest in earthen materials is primarily driven by their hygroscopic and thermo-buffering capabilities, which contribute to their superior indoor air quality. Stabilization is the commonly used solution to enhance their mechanical and hygrothermal properties. The current study uses an experimental approach to investigate the impact of cementitious stabilizers on the hygroscopic properties and thermal conductivity of rammed earth materials. Measured hygroscopic parameters included sorption isotherms, moisture buffering capacity, and water vapor diffusion resistance factor. The hygrothermal experiments were conducted on the unstabilized specimens with different water masses ranging from 5 to 15% and on the stabilized specimens with different cement content ranging from 5 to 20%. Finally, three mathematical models of Halsey, modified Chung-Pfost and Oswin were applied to the sorption isotherm data. The results showed that stabilization positively impacted decreasing the heat conduction and improving the hygroscopic properties of rammed earth materials. Among the three models, the modified Chung-Pfost model was the best fit for sorption isotherms.

Lightweight mortars with chalcedonite – Towards functional and durable materials for repair of historical masonry

In the repair of historical masonry and listed buildings, the requirements for compatibility and preservation of the original appearance and cultural and historical value of the rehabilitated structure are often discussed. In particular, technical, technological and material compatibility is often addressed by engineers and conservation professionals and the resulting solution often involves finding a compromise between an ideal, technically functional solution and preserving the historic value of the building for future generations. The material solution of mortars for repair of historical structures is based on the application of a suitable binder and porous filler, which allows achieve their high porosity, water vapor permeability, sufficient strength and durability. Obviously, there is no single ideal material solution for these mortars and it is always necessary to take into account the current state of the reconstructed structure and the composition and properties of the original materials in their design and application. The aim of the research presented here was to design and experimentally assess rendering and plastering mortars based on lime hydrate and natural hydraulic lime partially lightened with chalcedonite as a porous aggregate. The results of the material tests were compared with criteria imposed in WTA recommendation 2-9-03.2020/E. Chalcedonite was used as an alternative filler to silica sand and its application enabled the required values of porosity, compressive strength, water absorption coefficient and water vapor diffusion resistance factor to be achieved. The lightened plasters also showed increased hygroscopicity, low thermal conductivity and increased resistance to salt crystallization. Depending on the binder used and the demanded mechanical strength, the examined mortars thus represent materials applicable in the repair of damp and saline masonry of historical buildings.

Impact of Different Ratios of Lignin Waste and Liquid Glass on the Performance Characteristics of Biopolyurethane Foams.

In the current study, biopolyurethane foam was modified with 2.5-10 wt.% lignin waste (LigW) and liquid glass (LG)-modified LigW particles at different LigW/LG ratios-1:1 and 1:2-and their impact on performance characteristics-i.e., rheology, foaming times, apparent density, thermal conductivity before and after aging, dimensional stability at ambient and elevated conditions, compressive and tensile strengths, short-term water absorption by partial immersion, and water vapor permeability-was determined and evaluated. Structural analysis was implemented and structural parameters were taken into consideration as well. During the study, it was determined that 2.5-10 wt.% particles at the LigW/LG ratio of 1:2 showed a superior impact on the physical and mechanical properties of bioPUR foams. The apparent density only insignificantly increased and was in a density range suitable for commercially available polyurethanes. For particles at 10 wt.% and LigW/LG ratio of 1:1, the thermal conductivity value improved by 3.2%, the compressive strength increased by 153%, while the tensile strength improved by 23.5%, indicating sufficient interfacial adhesion between the filler and polymer matrix. Moreover, the short-term water absorption by partial immersion remained almost unchanged, while the water vapour diffusion resistance factor improved from 43 to 48. Additionally, the incorporation of LigW/LG 1:1 and LigW/LG 1:2 particles made it possible to obtain dimensionally and structurally stable closed-cell bioPUR foams for possible application as thermal insulation in building envelopes.

Identifying key parameters through a sensitivity analysis for realistic hygrothermal simulations at wall level supported by monitored data

The reliability of hygrothermal simulations of building components is key for designing energy efficiency measures, assessing living comfort, and preventing building damage. The model accuracy is related to the reliability of the selection of input parameters. Due to the high uncertainty, the selection of the input values is challenging. This work aims to calibrate a hygrothermal simulation model exploiting monitored values recorded in a case study located in Settequerce (Italy), to understand how close to reality a numerical model can be. Moreover, a sensitivity analysis, based on the Morris method together with a Latin Hypercube sampling, is applied to identify the input parameters that affect most significantly the simulation. The results of the calibration indicated that is possible to obtain reliable outputs by appropriately selecting materials within the database. The sensitivity analysis showed that the relative humidity under the insulation is largely influenced by the water vapor diffusion resistance factor of the plaster, applied during the renovation phase both on the internal and external side. Among the coefficients describing the coupling with the boundary conditions, only the external convective heat coefficient and the coefficient of short-wave solar radiation influence slightly the objective function.

Water vapor transmission parameters of the Kežmarok sandstone

Dynamic complex heat and water transport in building constructions can be calculated using modern simulation software such as Wufi, Delphin, Math, Comsol Multiphysics and other. This software is suitable for the evaluation of the thermal and hygric processes in constructions of historical buildings. Because it includes many important factors such as dynamic boundary conditions, solar radiation, driven rain, ground water, diffusion and others. The heat and water transport parameters of historical materials are needed for simulation of coupled heat and water transport in building materials. The Kežmarok sandstone was chosen for analysis. One of the important material parameters for evaluation of complex heat and water transport in building constructions are water vapor transmission parameters. Vapor transport can be described as water vapor diffusion resistance factor, water vapor diffusion coefficient and diffusion equivalent air layer thickness. The dry cup and wet cup method were used to determine the water vapor transmission parameters of Kežmarok sandstone.

EFFECT OF ALKOXYSILANE-BASED TREATMENT ON THE DURABILITY OF NORTH CYPRUS STONES FOR CONSTRUCTION

ABSTRACT Limestones are generally vulnerable to various weathering effects, hence, protection and consolidation of them is necessary. Locally available limestones of Northern Cyprus have been used in both historical buildings dated back to the 16th century for conservation applications and new buildings mostly as a cladding material. However, certain decay patterns exist on these stones. In the current study, the service life of Cyprus stones was inspected. Alkoxysilane-based consolidation and protection treatments were applied on new quarried stones to enhance the stone properties and aged stones to conserve and protect the architectural heritage. Service life assessment was performed by applying accelerated aging tests on both new and aged stones before and after treatments. The treatments improved the physical, mechanical and durability properties of the stones in terms of unchanging the water vapor diffusion resistance factor, decreasing the porosity and the water absorption ratio, increasing the ultrasound pulse velocity, the compressive and the flexural strengths, and improving the resistance of the stones against wetting-drying, freeze-thaw, salt crystallization and SO2 vapour effects. The combination of consolidation and protection treatment (K2) was more efficient on the properties of the stones compared to only protection treatment (K1) due to the better penetration capacity, higher decreasing ratio of the porosity, and higher improvement of the physical, mechanical and durability properties. The treatments also improved the properties of the aged stones; thus, it may be inferred that treatment would benefit the conservation of historical buildings.

Research of Wood Waste as a Potential Filler for Loose-Fill Building Insulation: Appropriate Selection and Incorporation into Polyurethane Biocomposite Foams.

Currently, the recycling potential of wood waste (WW) is still limited, and in a resource efficiency approach, recycling WW in insulation materials, such as polyurethane (PUR), appears as an appropriate solution. It is known that the quality of WW is the main aspect which influences the stability of the final products. Therefore, the current study analyses different WW-based fillers as possible modifiers for polyurethane biocomposite foams for the application as loose-fill materials in building envelopes. During the study of WW-based fillers, it was determined that the most promising filler is wood scobs (WS) with a thermal conductivity of 0.0496 W/m·K, short-term water absorption by partial immersion—12.5 kg/m2, water vapour resistance—0.34 m2·h·Pa/mg and water vapour diffusion resistance factor—2.4. In order to evaluate the WS performance as a filler in PUR biocomposite foams, different ratios of PUR binder and WS filler (PURb/WS) were selected. It was found that a 0.40 PURb/WS ratio is insufficient for the appropriate wetting of WS filler while a 0.70 PURb/WS ratio produced PUR biocomposite foams with the most suitable performance: thermal conductivity reduced from 0.0523 to 0.0476 W/m·K, water absorption—from 5.6 to 1.3 kg/m2, while the compressive strength increased from 142 to 272 kPa and the tensile strength increased from 44 to 272 kPa.

WATER VAPOR TRANSPORT IN PLASTERS CONTAINING SUPERABSORBENT POLYMERS

A proper characterization of material properties represents an important step towards an efficient building design. Considering the present issues in the construction sector, moisture loads pose a risk not only to increased material deterioration but also to the health of building inhabitants. In this paper, modified plaster mixtures with superabsorbent admixture are designed in order to improve passive moderation of finishing layers against varying humidity conditions. The relationship between the amount of applied superabsorbent admixture and resulting water vapor transport properties is identified and the influence of temperature on water vapor transport is analyzed. The steady-state cup method is used for the determination of water vapor transport properties, namely the water vapor diffusion permeability, water vapor diffusion coefficient and water vapor diffusion resistance factor. The obtained data show temperature as a very significant factor affecting water vapor transport in the analyzed plasters. Considering the dry-cup method arrangement, relative humidity probes should be used for monitoring relative humidity under the sealed sample for a sufficiently precise determination of water vapor pressure gradient.

Basic Physical, Mechanical, Thermal and Hygric Properties of Concrete with Coarse Aggregates Fabricated from Recycled Concrete Pavements

Concrete production unfavourably affects the environment due to high energy demands of cement production and consumption of limited natural resources. Therefore, waste utilization in fabrication of cementitious material is beneficial and legitimate. Significant reduction of environmental impact can be secured by utilization of various types of wastes or byproducts used for a partial substitution of cement binder or aggregates. However, the use of waste materials usually leads to deterioration of material properties of the designed composites. Therefore, it is very important to thoroughly investigate important materials properties to verify performance and practical usability of the newly designed materials. In this paper, three types of concrete mixes were designed. The reference concrete involved fine and coarse natural riverbed aggregates and two other mixes were designed using both, natural and recycled aggregates represented by crushed concrete paving cobbles. Concretes were tested in terms of basic physical properties (bulk density), mechanical properties (compressive strength), thermal properties (thermal conductivity, specific heat capacity, thermal diffusivity), and hygric properties (water vapour diffusion resistance factor, water vapour sorption at 97% RH, water absorption coefficient, moisture diffusivity) and experimentally determined data were compared and discussed. It was observed that materials properties of concretes with recycled aggregates are comparable with those of the reference concrete which is a promising fact from the environmental point of view.

On the importance of desiccant during the determination of water vapor permeability of permeable insulation material

Water vapor permeability of building materials is usually measured using dry cup test according to the ISO 12572 standard. For this test, suitable adsorbing desiccant should be used to provide stable low vapor pressure conditions within the cup and, thus, to ensure the good accuracy of the measurement. In this work, different adsorbing desiccants mentioned in the ISO 12572 standard are tested for measurements performed on wood fiber insulation. For each experiment, relative humidity is monitored inside the dry cup. The results indicate that 0 %RH is not reached inside the dry cup and boundary condition is not always stable for highly permeable construction materials, depending on the adsorbing desiccants. The impact of these observation is evaluated on the determination of water vapor diffusion resistance factor and compared to other sources of uncertainties.

Hygrothermal properties of light-earth building materials

This experimental study provides complete datasets of hygrothermal properties of numerous hemp-clay with density ranging from 200 to 350 kg m-3 for building thermal insulation. In addition, attention is also paid on protocols and methods, on the measurements repeatability and on the influence of conditioning temperature and relative humidity: mean uncertainties do not exceed 10% for all measurements, while initial conditioning influences at most the results, particularly for the sorption isotherm. Heat and moisture storage properties depend obviously of the constituent (hemp or clay). Furthermore, they can be estimated with a good accuracy with a mixing law. Thermal conductivity of the composites ranges between 0.06 and 0.12 W m-1 K-1 and clearly depends on the density. Water vapor diffusion resistance factor ranges between 2.24 and 4.14, while capillary absorption coefficient ranges between 0.027 and 0.135 kg m-2 s-0.5.

Investigation of engineering properties for usability of Lefke stone (Osmaneli/Bilecik) as building stone

Lefke stone is a sandstone that has been widely used in mosques, madrasas, churches, and houses as building stone. The geological features and engineering properties of Lefke stone outcropped in the southern part of Osmaneli/Bilecik were investigated in field and laboratory studies. Samples acquired during the fieldwork were tested to determine the physical, mechanical, durability, and hygrothermal properties in the laboratory. The mean physico-mechanical properties of Lefke stone yielded apparent density of 2.38 g/cm3, specific gravity of 2.68 g/cm3, total porosity of 11.26%, 2.93% water absorption by weight, uniaxial compressive strength of 94 MPa, flexure strength of 11.45 MPa, a 3.90 MPa point load strength, 4.5–5 Mohs hardness, and field Schmidt hammer rebound value of 36. According to durability tests, Lefke stone is resistant to CaCl2 salt mist but has low resistance to SO2 aging. Salt crystals placed in the discontinuities of the rock caused slight crack growth. The stone’s resistance to crystallization of sodium sulphate salt is low, and an increase in the volume of salts crystallized in the rock results in low corner strengths. A capillary water-absorption value of 0.0016 kg/m2.h places Lefke stone into the category of very low water absorption capacity and permeability. The water vapor diffusion resistance factor (μ) less than 1 indicates that the sandstone has high breathability. Its performance in historical buildings, field observations, and values obtained through laboratory tests confirm that Lefke sandstone can be used as a building stone.

Moisture-mechanical performance improvement of thermal insulating polyurethane using paper production waste particles grafted with different coupling agents

Abstract Current efforts are focused on transforming renewable resources into advantageous polymers and the utilisation of waste for the same application and others. However, the utilisation of waste into polymer systems causes forming mixtures with high viscosities; therefore, this study analyses different types of titanate coupling agents (TCAs), TCA-L44, TCA-L38 and TCA-K44, and their effects on the rheology of bio-based polyol premixes filled with paper waste particles and the physical-mechanical properties and microstructures of polyurethane foams (RPUFs). It is found that TCAs improve the dynamic viscosity of polyol premixes by a factor of two. Based on the scattering of the apparent density results, TCA-L44 and TCA-K44, at amounts of 1–3 wt%, ensure an even distribution of waste particles, while TCA-L38 does not show evidence of coupling. Compared to RPUF without TCAs, the apparent density increased on average from ∼65 to ∼69 kg/m3 for TCA-L44, to ∼71 kg/m3 for TCA-L38 and to 69 kg/m3, indicating a weak cross-link effect. The compressive strength increases by an average of 6.5–9.1% and the tensile strength increases by 26.0–42.2% when TCA-K44 is used, while the water absorption decreases by up to ∼62% and the water vapour diffusion resistance factor decreases by ∼39% when TCA-L44 is used.

Hygric and mechanical parameters of ternary binder based plasters lightweighted by expanded perlite

This article is focused on modern plasters with improved thermal insulating ability. The studied plasters were composed of lime, cement, ceramic powder, expanded perlite and silica sand. Regarding the matrix, three kinds of binders were used. Lime was partially replaced by ceramic powder. These waste materials show good pozzolanic reactivity and thus bring economic and ecological benefits. Portland cement was added as a third component to the mixture for the purpose of improving mechanical performance of the studied plasters. In this article, mechanical properties of designed plasters are presented. It was proved that matrix strengthening brought positive effect and eliminated the deterioration of mechanical behaviour; the final values of compressive strength were over 3 MPa. Due to desired high porosity of the studied plasters, their durability can be strongly affected by presence of the water. Therefore, in this article, the hygric parameters were studied too. Namely, the water absorption coefficient, apparent moisture diffusivity, the water vapour diffusion resistance factor and sorption and desorption isotherms belong among studied hygric characteristics. In this article, pore size distribution curves, which affect the discussed parameters, are presented.

Wood waste as an alternative thermal insulation for buildings

Current insulation materials in the construction market, which are predominantly inorganic materials, have a high performance in relation to heat transfer, i.e. high R-values, but the environmental impacts in their production processes are significant. The use of bio-based natural fibre materials such as cork, cotton, wood fibre, hemp, etc. with their lower embodied energy, moisture buffering capacity and, consequently, improved Indoor Environmental Quality have received increasing focus in both research and application, particularly amongst environmentally-conscious clients and designers.In this study a natural fibre material in the form of wood waste is examined experimentally to assess its suitability for use as a thermal insulation material, without the addition of any binder, within a timber frame wall construction. The wood waste is from primary production sources using untreated material. According to our experimental results, the thermal conductivity values of wood waste with different densities, ranged from 0.048 to 0.055 W/mK. These values are slightly higher than commonly used inorganic based insulation materials, although comparable to other natural insulation materials in the market, but have the economic advantage of being a low-cost by-product. The values relating to the material hygric performance including the water vapour diffusion resistance factor, water vapour permeability, and water absorption coefficient were also determined and presented, which will help facilitate future hygrothermal modelling.

Heat and moisture transfer behaviour in Phyllostachys edulis (Moso bamboo) based panels

This study focuses on the heat and moisture transfer behaviours in the Phyllostachys edulis (Moso bamboo) panels at various temperature and relative humidity (RH) conditions. Moso bamboo panels with different lamination methods were prepared by assembling bamboo strips from different layers of the bamboo culm wall. Dynamic coupled heat and moisture transfer experiments were conducted. Unsteady state numerical modelling was conducted by COMSOL Multiphysics™. A rigorous approach was adopted in this paper. A series of parametric studies of numerical simulation are firstly presented in this paper and then validated by the experiments. Both experimental and simulation results appear to be consistent with the results of measurements of the basic hygrothermal parameters, which demonstrates the robustness of the results. The temperature and RH results indicated that although the panel made from layers of the internal part of bamboo culm wall can provide good insulation performance, its ability to resist high RH variation is inferior to the layer from the external part of bamboo culm wall. The parametric study found that density is the most critical parameters to influence the temperature distributions in the transient state. The thermal conductivity dominates the temperature variation in the steady state. The water vapour diffusion resistance factor is the key parameter which influences the RH simulation results. Numerical simulation with moisture transfer shows better consistency than the simulation without moisture in both equilibrium and transient states. The results of this study demonstrated that the external part of the bamboo culm wall can be utilised to minimise the RH variation of the panel while the internal part is suitable for increasing the thermal insulation performance of the panel.

Hygrothermal properties of clayey plasters with olive fibers

This research deals with how to use agricultural waste materials in constructions considering that the development of innovative materials has to respond to both environmental and energy issues. The leaves and the small branches derived from the pruning of olive trees were incorporated, after drying, into a clay-sand mixture to obtain a bio-based plaster. Earthen samples, containing different percentages of olive fibers, were prepared and tested to investigate their hygrothermal behaviour. Thermal conductivity and the effects of several parameters on thermal performance were analyzed. The evaluation of the hygric behaviour was based on the measurement of the water vapour diffusion resistance factor and of the isothermal sorption curves. Results showed that the addition of olive fibers in the earth matrix enhances the insulating and hygric performances. The ability of the material to exchange moisture was studied by calculating the ideal Moisture Buffering Value (MBVideal). Results showed that the effects of moisture adsorption/desorption improved with the increase of the fibers content.

Hygrothermal properties of bio-insulation building materials based on bamboo fibers and bio-glues

This study focuses on manufacturing by thermo-pressing new low-environmental-impact bio-insulation fiberboards from bamboo fibers and bone glue, modified with sodium lignosulfonate. The aims are to measure moisture buffer value, water vapor permeability, bending properties, thermal conductivity and vapor sorption isotherms of these materials. The moisture buffer values of these materials belong to the “excellent” category, ranging from 2.5 to 3.9g/(m2.%RH), higher than the value for bamboo fiberboard without glue (1.7g/(m2.%RH). The water vapor diffusion resistance factor ranges from 8 to 17, which is similar with other fiber insulation materials. The bending properties show a significant improvement when 30% (w/w) glue is used, the glue being a mixture between bone and sodium lignosulfonate glues. Moreover, the variation in thermal conductivity of the fiberboards with relative humidity and moisture content is investigated to evaluate the hygrothermal performance of the fiberboards. The results are promising for both thermal insulation and moisture buffering, thus these fiberboards could be used for passive control of indoor environment.