Search

In the context of the energy transition, new construction materials are emerging, notably bio-based materials such as wood concrete. This paper investigates the hygrothermal performance of walls constructed with wood–cement concrete. First, the thermal properties of wooden concrete, namely thermal conductivity, effusivity, and diffusivity, are experimentally characterized in both dry and wet conditions. Second, in situ measurements are carried out on a house in Lyon, a city in France, constructed with mono-layered wood–cement walls. This involves monitoring the temperature and relative humidity levels both inside and outside the building, as well as at three distinct positions within the wood walls over a 6-month period (from 20 April 2023 to 20 October 2023). The hygrothermal analysis at the center of the wall reveals that the wood wall effectively moderates fluctuations in the external temperature and relative humidity. Following this, a numerical study is performed to check the reliability of the adopted Reduced Heat, Air, and Mass (HAM) model to reproduce the hygrothermal performance of the wood–cement wall. The results show a strong agreement between the simulated and measured data, confirming the applicability of the 'Reduced HAM' model for the prediction of the hygrothermal behavior of wood–cement walls. [ABSTRACT FROM AUTHOR]

Straw bale building construction is attracting a revived public interest because of its potential for reduced carbon footprint, hygrothermal comfort, and energy savings at an affordable price. The present paper aims to summarize the current knowledge on straw bale construction, using available data from academic, industry, and public agencies sources. The main findings on straw fibers, bales, walls, and buildings are presented. The literature shows a wide variability of results, which reflects the diversity of straw material and of straw construction techniques. It is found that the effective thermal conductivity, density, specific heat, and elastic modulus of straw bales used in construction are in the range 0.033–0.19 W/(m·K), 80–150 kg/m3, 1075–2000 J/(kg·K), and 150–350 kPa respectively. Most straw-based multilayered walls comply with fire resistance regulations, and their U-value and sound reduction index range from 0.11 to 0.28 W/m2 K and 42 to 53 dB respectively, depending on the wall layout. When compared to standard buildings, straw bale buildings do provide yearly reductions in carbon emissions and energy consumption. The reductions often match those obtained after applying energy-saving technologies in standard buildings. The paper ends by discussing the future research needed to foster the dissemination of straw bale construction. [ABSTRACT FROM AUTHOR]

The experimental data retrieved from three-dimensional particle tracking velocimetry (3D PTV) are crucial for indoor environment engineering when designing ventilation strategies or monitoring airborne pollutants dispersion in inhabited spaces as well as in livestock compounds. The performance of the measurement algorithm, as the core part of the 3D PTV technology, has a strong influence on the final results. This study presents a method to select the better 3D PTV algorithm depending on the application targeted. This study first compared the performance of seven 3D PTV algorithms on two types of 3D laminar macro scale flows of known Navier–Stokes solutions, namely the Kovasznay and Beltrami flows. The comparison was based on the accuracy, the measuring volume coverage and the achievable trajectory length of each algorithm with respect to the particle tracking density and the total number of frames. Then, the measurement algorithms with better performances were further compared with the experimental measurement of real 3D airflows in a cubic cavity. The results suggest that different measurement algorithms have different advantages and drawbacks depending on the application targeted, and that the algorithms using the epipolar constraint as the method of spatial matching generally perform better. [ABSTRACT FROM AUTHOR]

In France, renovation of existing buildings has a high priority. The thickness of insulation layers becomes a major issue of concern especially in cities. In this study, we present a recently developed insulating rendering based on silica aerogels that can be applied to new buildings and to retrofit existing ones. A full scale experimental house is built near Chambery in France, with the rendering applied on its external facades. The results of a numerical model developed in EnergyPlus are compared to the on-site measurements. After validating the numerical model, the thickness of the rendering is optimized based on a cost analysis for different climates for the case of retrofitting an old building. Then, a sensitivity analysis is carried out to determine the thickness dependency on annual heating load, present worth factor, rendering’s cost, and heating set-point. Results show that the optimum rendering thickness is in the range of 1.7–4.4 cm and the payback period in the range of 1.4–2.7 years depending on the climate. The optimum thickness increases with the increasing heating set-point and increasing present worth factor; however, it decreases with the increasing rendering cost. [ABSTRACT FROM AUTHOR]

Highlights: [•] A volume force was added to the buoyancy term in the Navier–Stokes’ momentum conservation equation. [•] Using PCM kept panel temperature under 40°C for 80min under radiation of 1000W/m2. [•] Adding cooling fins does not always help maintaining the panels’ temperature low. [ABSTRACT FROM AUTHOR]

Abstract Worldwide, the residential buildings are consuming a considerable amount of energy. The high potential of buildings towards energy efficiency has drawn special attention to the passive design parameters. A comprehensive study on optimal passive design for residential buildings is presented in this paper. Twenty-five different climates are simulated with the aim to produce best practices to reduce building energy demands (for cooling and heating) in addition to the life-cycle cost (LCC). The occupants' adaptive thermal comfort is also improved by implementing the appropriate passive cooling strategies such as blinds and natural ventilation. In this respect, the implemented methodology is composed of four phases: building energy simulation, optimization, Multi-criteria Decision Making (MCDM), sensitivity study, and finally an adaptive comfort analysis. An optimal passive solution of the studied building indicates the potential to save up to 54%, 87% and 52% of the cooling demands (Qcool), heating demands (Qheat) and LCC respectively with respect to the initial configuration. The obtained optimal passive parameters are validated with the National Renewable Energy Laboratory NREL benchmark for low energy building's envelope. Additionally, the integrated passive cooling strategies have demonstrated its competency since it leads to a significant overheating decrease. Highlights • Residential building's passive design parameters are optimized. • Effect of different climates of Köppen Geiger classification is studied. • Thermal comfort and energy performance of the case-studies are significantly enhanced. • Passive cooling strategies lead to adequate thermal comfort and fewer cooling systems. [ABSTRACT FROM AUTHOR]

Solar Photovoltaic (PV) cells can absorb up to 80% of the incident solar radiation obtained from the solar band, however, only a small amount of this absorbed incident energy is transformed into electricity depending on the conversion efficiency of the PV cells and part of remainder energy increases the temperature of PV cell. High solar radiation and ambient temperature lead to an elevated photovoltaic cell operating temperature, which affects its lifespan and power output adversely. Number of techniques have been attempted to maintain the temperature of photovoltaic cells close to their nominal operating value. In the present review various cooling techniques such as natural and forced air cooling, hydraulic cooling, heat pipe cooling, cooling with phase change materials and thermoelectric cooling of PV panels are discussed at length. It is important to note that, though cooling techniques are highly needed to regulate the PV module temperature, especially for mega installations, these should be economically viable too. [ABSTRACT FROM AUTHOR]