Experimental study on the deterioration of thermal insulation performance due to wind washing of the cavity insulation in leaky walls

Kosiński, Piotr; Wójcik, Robert; Semen, Beata

doi:10.1080/23744731.2019.1634420

Cited by 10 publications

(6 citation statements)

References 11 publications

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“…The energy demand of buildings can be reduced by thermally insulating the houses. Nowadays, even the previously insulated buildings should receive additional thermal protection to meet regulations or repair previous building construction mistakes that cause defects and mechanical, chemical, environmental, or hygrothermal deteriorations, or accelerate natural aging [ 3 , 4 , 5 , 6 ].…”

Section: Introductionmentioning

confidence: 99%

Heat Transfer in Straw-Based Thermal Insulating Materials

2021

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An analytic-empirical model was developed to describe the heat transfer process in raw straw bulks based on laboratory experiments for calculating the thermal performance of straw-based walls and thermal insulations. During the tests, two different types of straw were investigated. The first was barley, which we used to compose our model and identify the influencing model parameters, and the second was wheat straw, which was used only for validation. Both straws were tested in their raw, natural bulks without any modification except drying. We tested the thermal conductivity of the materials in a bulk density range between 80 and 180 kg/m3 as well as the stem density, material density, cellulose content, and porosity. The proposed model considers the raw straw stems as natural composites that contain different solids and gas phases that are connected in parallel to each other. We identified and separated the following thermal conductivity factors: solid conduction, gas conduction in stem bulks with conduction factors for pore gas, void gas, and gaps among stems, as well as radiation. These factors are affected by the type of straw and their bulk density. Therefore, we introduced empirical flatness and reverse flatness factors to our model, describing the relationship between heat conduction in stems and voids to bulk density using the geometric parameters of undisturbed and compressed stems. After the validation, our model achieved good agreement with the measured thermal conductivities. As an additional outcome of our research, the optimal bulk densities of two different straw types were found to be similar at 120 kg/m3.

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Section: Introductionmentioning

confidence: 99%

Heat Transfer in Straw-Based Thermal Insulating Materials

2021

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“…Such air flows can dramatically change the n 50 factor in the case of natural fibrous insulation, while with mineral wool, it will change only to a limited extent. However, it should be noted that n 50 is an important factor when investigating air infiltration but gives no information about wind washing [41].…”

Section: Resultsmentioning

confidence: 99%

“…The pressure loads were activated after thermal equilibrium of the model, for various times, from 30 to 180 min, with time step of 30 min. The authors opted for short periods of pressure load, because only long periods have been analyzed so far [41]. The aim of the simulation was to establish the reaction time of the model on the pressure load and time of the model to return to equilibrium state.…”

Section: Simulationmentioning

confidence: 99%

Heat Losses Caused by the Temporary Influence of Wind in Timber Frame Walls Insulated with Fibrous Materials

et al. 2020

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The paper presents the results of research concerning three fiber materials—mineral wool, hemp fiber and wood wool—as loose-fill thermal insulation materials. The analysis used the material parameters determined in previous works conducted by the authors, such as thermal conductivity and air permeability in relation to bulk density. These materials exhibit open porosity; thus, convection is an essential phenomenon in the heat transfer process. The paper aimed at conducting thermal simulations of various frame wall variants which were filled with the above-mentioned insulation materials. The simulations were performed with the Control Volume Method using the Delphin 5.8 software. The studies accounted for the effect of wind pressure and the time of its influence on a wall insulated by means of fiber material with a thickness of 150 as well as 250 mm. The simulation enabled us to obtain such data as maximal R-value reduction and time to return to equilibrium after filtration for the analyzed materials. The study proved that heat transfer in these insulations strongly depends on the bulk density, thickness of the insulation and wind pressure. The decrease in R is reduced as the density increases. This results from the decreased air permeability characterizing the material. Wind washing causes lower R reduction than air filtration in all models. The greater the thickness, the longer it takes for the models to return to the equilibrium state following air filtration (and wind washing). This period is comparable for air filtration and wind washing. Hemp fibers were characterized with the strongest susceptibility to air filtration; in the case of wood wool, it was also high, but lower than for hemp fibers, while mineral wool was characterized with the lowest.

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“…3 with the measured lowest density and, at the same time, the lowest value of the thermal conductivity coefficient. The smallest Figure 8c presents a comparison between the results achieved for the tested moistened samples and the tested dry samples for a similar range of densities [38]. Observation of the results may lead to the conclusion that the values do not differ from each other by more than 1% (except for the extreme sample for the fourth series), which is below the measurement error of the device.…”

Section: Mineral Woolmentioning

confidence: 89%

Moisture Transport in Loose Fibrous Insulations under Steady-State Boundary Conditions

Kosiński

2023

Materials

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This research aimed to compare the transport capacity of loose-fill mineral wool, cellulose fibers, and wood wool to transfer moisture under steady-state conditions. The tests were carried out in the heat flow meter apparatus, which created a constant thermal field, limiting samples of sorptive moistened materials. The thermal conductivity, stabilization time, and moisture content of the samples were measured. Based on the variation in the results, the dynamism of moisture transport in the materials was determined. Mineral wool samples showed the lowest sorption. As a result, the moisture transport in this material stopped the fastest. In the case of cellulose and wood fibers, moisture transport continued throughout the whole test procedure. It was noted that the amount of moisture transport is influenced primarily by the structure of the fibers, the moisture content, and the possible presence of air in the pores. The wetter the material, the faster the transport. The dynamism of moisture transport according to trends of thermal conductivity changes over time was analyzed. The greater the slope of the linear regression line, the greater the dynamics of change. The smallest dynamics of change were found for mineral wool, for which the measured slope was between −0.008 and −0.033. For cellulose and wood wool, the range of slope was from −0.141 to −0.210, and from −0.162 to −0.211, respectively. The results of this research may provide the basis for further work on buffering moisture in the adjacent internal layers of the frame walls.

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Experimental study on the deterioration of thermal insulation performance due to wind washing of the cavity insulation in leaky walls

Cited by 10 publications

References 11 publications

Heat Transfer in Straw-Based Thermal Insulating Materials

Heat Transfer in Straw-Based Thermal Insulating Materials

Heat Losses Caused by the Temporary Influence of Wind in Timber Frame Walls Insulated with Fibrous Materials

Moisture Transport in Loose Fibrous Insulations under Steady-State Boundary Conditions

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