Search Results (118)

Biosourced materials made of a combination of raw earth and fibers are attracting increasing interest for low-carbon construction due to their reduced environmental impact and good thermal and hygric performance. This study investigates several soil–fiber composites selected and formulated at different densities to assess their thermal conductivity, enabling the selection of two complementary materials: a structural earthen mix and a lightweight insulating mix. Experimental measurements were taken under controlled conditions and used to characterize heat and moisture fluxes, and numerical calculations were carried out to evaluate the performance of single and double-layer wall configurations. The results showed that an increase in thermal gradients accelerates vapor migration and alters the internal distribution of moisture. The evaluation of wall configurations demonstrated that placing the earthen insulating layer externally optimizes thermal fluxes and eliminates condensation risks at the interface between materials, while internal insulation can be sensitive to hygrothermal gradients and prone to moisture accumulation. The combined experimental–numerical approach provides new insights into high-performance designs of bio-based earthen envelopes, establishing guidelines for minimizing moisture-related risks in low-carbon building systems. Full article

The focus of this paper is on the large-format wooden panel painting Maundy Thursday Altarpiece from Southern Germany. Its wooden support and paint layer were severely damaged due to high climatic fluctuations, above all dryness. The aim of the research project was to develop a low-risk, conservatively acceptable procedure for controlled in situ humidification. In an interdisciplinary approach, a practical monitoring concept on-site was linked to art technology analyses, surface monitoring, hygrothermal simulations, and climate chamber tests. Based on the results, an individual climate corridor for controlled humidification of the case study was developed with the help of an enclosure and implemented in two gradual moistening phases. The combination of conservative support, measurement technology, and digital assessment allowed a controlled approach to a conservation optimum without other active interventions in the original material. The results highlight the need for object-specific strategies and humidity corridors at the interface between conservation, climate adaptation, and sustainability. A deviation from museum standard recommendations (depending on the guidelines 40–60% rH) shows the special challenges of monument preservation. Full article

Hygrothermal assessment plays a critical role in the design and maintenance of healthy, energy-efficient buildings. Despite established knowledge of condensation mechanisms and mitigation strategies, condensation and moisture remains a persistent issue even in newly constructed structures. This ongoing challenge highlights the need for empirical validation of data critical to condensation occurrence. This study presents the development and evaluation of a mobile, on-site measurement system designed to collect data on surface condensation and thermal conductivity of building walls. The system is developed using a data acquiring and processing platform myRIO built around LabVIEW, enabling real-time detection of critical condensation conditions and deviations in thermal conductivity from measured values. Measurement results were validated with the Heat Flow Method (HFM) and theoretical calculations at the same site. Full article

As an eco-friendly natural building material, rammed earth possesses outstanding hygrothermal performance, which plays a vital role in achieving the goals of sustainable architecture. However, most existing simulations assume constant hygrothermal parameters, resulting in considerable discrepancies between predicted and actual energy performance and consequently underestimating the true passive regulatory potential of rammed earth. To enhance the accuracy of energy consumption predictions in rammed earth buildings, this study integrates experimental measurements with dynamic simulations and experimentally determines both the constant and non-constant hygrothermal parameters of rammed earth. By integrating experimental and simulation approaches, this study reveals a strong positive linear correlation between the thermal conductivity of rammed earth and its moisture content (R² = 0.9919), increasing from 0.77 W/(m·K) to 1.38 W/(m·K) as moisture content rises from 0% to 14%, whereas the moisture resistance factor decreases exponentially with increasing relative humidity (RH). Subsequently, the two sets of hygrothermal parameters were implemented in the WUFI-Plus simulation platform to conduct annual dynamic simulations across five representative Chinese climate zones (Harbin, Beijing, Nanjing, Guangzhou, and Dali), systematically comparing the performance differences between the “non-constant” and “constant” parameter models. The results show that the non-constant parameter model effectively captures the dynamic hygrothermal regulation of rammed earth, exhibiting superior passive performance. It predicts substantially lower building energy loads, with heating energy reductions most pronounced in Harbin and Beijing (16.9% and 15.5%) and cooling energy reductions most significant in Guangzhou and Nanjing (15.8% and 15.2%). This study confirms that accurately accounting for the dynamic hygrothermal coupling process is fundamental to reliably evaluating the performance of hygroscopic materials such as rammed earth, providing a robust scientific basis for promoting energy-efficient, low-carbon, and climate-responsive sustainable building design. Full article

Achieving a decarbonized built environment in Canada requires proven, resilient, and scalable building envelope assemblies. In 2022, building operations accounted for 18% of Canada’s greenhouse gas (GHG) emissions, with space heating responsible for nearly two-thirds of this total. Alongside operational carbon reductions, embodied carbon emissions—stemming from the production and transport of building materials—must be prioritized during the design phase. Without intervention, construction materials could consume up to half of the remaining global 1.5 °C carbon budget by 2050. This paper highlights NRCan’s prototype, low-carbon, prefabricated panels filled with chopped straw and cellulose insulation under the Prefabricated Exterior Energy Retrofit (PEER) research project. The research advances confidence in performance and durability of biogenic materials by conducting controlled experiments, guarded hot box testing, and hygrothermal modelling. These panels present a promising pathway to drastically lower embodied carbon in the built environment. The validated hygrothermal model, accurate to between 3% and 7, enables assessment of hygrothermal performance across Canadian climates, retrofit scenarios and future climate conditions. This work supports the evidence for low-carbon or bio-based materials as a solution for Canada’s built environment. Full article

The paper presents select in situ and numerical investigations related to improving the energy efficiency of historic buildings. Using the case study of a historic timber building as an example, the procedure of the in situ investigation of its existing condition is presented. This procedure included measuring the moisture of the timber elements, determining the presence of fungi, mold, and wood-destroying insects, infrared camera inspection, and measuring the microclimate of the rooms. According to the conclusions of the building survey report, conservation guidelines were proposed. On the basis of those proposed guidelines, thermal upgrades were suggested, including insulation on the inside of the envelope components. Detailed numerical calculations were provided for the proposed thermal insulation systems. Those included a hygrothermal performance evaluation in the context of the change in the moisture content of timber elements in the insulated envelope components. The risk of mold development on the surface of selected junctions was also estimated. The key outcome of this study is a proprietary procedure for improving the thermal protection quality of envelope components of historic timber buildings. Full article

Deep retrofits are one of the few pathways to decarbonize the existing building stock while simultaneously improving climate resilience. These retrofits improve insulation, airtightness, and mechanical equipment efficiency. NRCan’s Prefabricated Exterior Energy Retrofit (PEER) project developed prefabricated building envelope retrofit solutions to enable net-zero performance. The PEER process was demonstrated on two different pilot projects completed between 2017 and 2023. In 2024, in partnership with industry partners, NRCan developed new low-carbon retrofit panel designs and completed a pilot project to evaluate their performance and better understand resiliency and occupant comfort post-retrofit. The Low-Carbon Climate-Resilient (LCCR) Living Lab pilot retrofit was completed in 2024 in Ottawa, Canada, using low-carbon PEER panels. This paper outlines the design and construction for the pilot, including panel designs, the retrofitting process, and post-retrofit building and envelope commissioning. The retrofitting process included the design and installation of new prefabricated exterior retrofitted panels for the walls and the roof. These panels were insulated with cellulose, wood fibre, hemp, and chopped straw. During construction, blower door testing and infrared imaging were conducted to identify air leakage paths and thermal bridges in the enclosure. The retrofit envelope thermal resistance is RSI 7.0 walls, RSI 10.5 roof, and an RSI 3.5 floor with 0.80 W/m²·K U-factor high-gain windows. The measured normalized leakage area @10Pa was 0.074 cm²/m². The net carbon stored during retrofitting was over 1480 kg CO₂. Monitoring equipment was placed within the LCCR to enable the validation of hygrothermal models for heat, air, and moisture transport, and energy, comfort, and climate resilience models. Full article

Internal insulation plasters enable historic building renovation without altering the external appearance of the wall. However, the use of internal insulation must be verified case-by-case through dynamic hygrothermal simulation, and the influence of input parameters on the results is not always clear. This paper aims to (i) characterize a new lime-based insulating plaster with expanded recycled glass and aerogel through laboratory measurements, (ii) assess the damage criteria of the plaster under different boundary conditions through dynamic simulations, and (iii) identify the most impactful design conditions on the relative humidity behind insulation. This innovative plaster combines highly insulating properties (thermal conductivity of 0.0463 W/mK) with good capillary activity while also integrating recycled components without compromising performance. The relative humidity behind insulation remains below 95% in most simulated scenarios, with cases above this threshold found only in cold climates, particularly under high internal moisture loads. The parametric study shows that (i) in the analyzed stones, the thermal conductivity variation of the existing wall has a greater effect on the relative humidity behind insulation than the variation of the vapor resistance factor, (ii) the effect of insulation thickness on the relative humidity behind insulation depends on the difference in thermal resistance of the insulation and existing masonry layers, and (iii) internal moisture load and external climate directly impact the relative humidity behind insulation. Full article

This article presents a comparative evaluation of three established thermal comfort models (ISSO 74, ASHRAE 55, and EN 16798-1) in the context of residential buildings in Algiers, under current and projected Mediterranean climate conditions. By combining field measurements, occupant interviews, and dynamic simulations in DesignBuilder, this research analyzes thermal comfort responses using the RCP 8.5 climate scenario. The analysis demonstrates that ISSO 74 is more suitable for temperature adaptation, while EN 16798-1 offers better humidity tolerance in high-moisture environments. Results reveal that indoor thermal discomfort currently affects more than one-third of the annual hours, with summer discomfort projected to dominate by 2100. Bedrooms are identified as the most thermally vulnerable spaces during peak summer weeks. The article identifies a critical mismatch between existing comfort standards and local climatic realities, calling for the development of an adaptive thermal comfort model tailored to the socio-economic and hygrothermal characteristics of North African cities. Passive strategies and mixed-mode ventilation are recommended as essential for enhancing climate resilience and reducing energy demand. Full article

The increased complexity of buildings has led to rigorous performance demands from materials and building envelopes. As markets for low-carbon, renewable construction materials grow, cross-laminated timber and wood fiber insulation have emerged as promising alternatives to meet these rigorous demands. However, an investigation into the performance and interaction of materials within high-performance systems is necessary to determine the durability risks associated with increased complexity and the introduction of new materials. This is important in order to ensure that these materials can meet the required functions of the building while taking advantage of their environmental benefits. To do so, this case study investigated a building constructed of cross-laminated timber and wood fiber insulation in a cold climate (Zone 6A) (Belfast, ME, USA). During construction, the building was instrumented with temperature, relative humidity, and moisture content monitoring instrumentation through the envelope, i.e., wall and roof assemblies. The conditions within the envelope were monitored for a two-year period and used to calibrate a hygrothermal model, along with measured material properties. The calibrated model was used to conduct a 5-year simulation and mold risk assessment. Findings demonstrated that there was no moisture or mold risk throughout the monitoring period or simulation. This supports the integration of cross-laminated timber and wood fiber insulation in sustainable building practices, particularly in cold climates where moisture management is critical. Full article

Optical fiber composite insulators are essential for photoelectric current measurement, yet insulation failure at embedded optical fiber interfaces remains a major challenge to long-term stability. This study proposes a strategy to replace conventional silicone rubber with cycloaliphatic-like epoxy resin (CEP) as the shed-sheathing material. Three optical fibers with distinct outer coatings, ethylene-tetrafluoroethylene copolymer (ETFE), thermoplastic polyester elastomer (TPEE), and epoxy acrylate resin (EA), were evaluated for their interfacial compatibility with CEP. ETFE, with low surface energy and weak polarity, exhibited poor wettability with CEP, resulting in an interfacial tensile strength of 0 MPa, pronounced dye penetration, and rapid electrical tree propagation. Its average interfacial breakdown voltage was only 8 kV, and the interfacial leakage current reached 35 μA after hygrothermal aging. In contrast, TPEE exhibited high surface energy and strong polarity, enabling strong bonding with CEP, yielding an average interfacial tensile strength of approximately 46 MPa. Such a strong interface effectively suppressed electrical tree growth, increased the average interfacial breakdown voltage to 27 kV, and maintained the interfacial leakage current below 5 μA even after hygrothermal aging. EA exhibited moderate interfacial performance. Mechanism analysis revealed that polar ester and ether groups in TPEE enhanced interfacial electrostatic interactions, restricted the mobility of CEP molecular chain segments, and increased charge traps. These synergistic effects suppressed interfacial charge transport and improved insulation strength. This work offers valuable insight into structure–property relationships at fiber–resin interfaces and provides a useful reference for the design of composite insulation materials. Full article

This study investigates the coupled hygrothermal behavior of mycelium-based composites (MBCs) as a function of their microstructural organization, governed by fungal species, substrate type, additive incorporation, and treatment method. Eleven composite formulations were selected and characterized using a multi-scale experimental approach, combining scanning electron microscopy, dynamic vapor sorption, vapor permeability tests, capillary uptake measurements, and transient thermal conductivity analysis. SEM analysis revealed that Ganoderma lucidum forms dense and interconnected hyphal networks, whereas Trametes versicolor generates looser, localized structures. These morphological differences directly influence water vapor transport and heat conduction. Additive-enriched composites exhibited up to 21.8% higher moisture uptake at 90% RH, while straw-based composites demonstrated higher capillary uptake and free water saturation (up to 704 kg/m³), indicating enhanced moisture sensitivity. In contrast, hemp-based formulations with Ganoderma lucidum showed reduced sorption and vapor permeability due to limited pore interconnectivity. Thermal conductivity varied nonlinearly with temperature and moisture content. Fitting the experimental data with an exponential model revealed a moisture sensitivity coefficient thirty times lower for GHOP compared to VHOP, highlighting the stabilizing effect of a compact microstructure. The distinction between total and effective porosity emerged as a key factor in explaining discrepancies between apparent and functional moisture behavior. These findings demonstrate that hygric and thermal properties in MBCs are governed not by porosity alone, but by the geometry and connectivity of the internal fungal network. Optimizing these structural features enables fine control overheat and mass transfer, laying the groundwork for the development of high-performance, bio-based insulation materials. Full article

As energy-efficient buildings become central to climate change mitigation, the opportunity for interior and interstitial moisture accumulation and mould growth can increase. This study investigated the potential simulation-based mould growth risks associated with the current generation of insulated low-rise timber framed external wall systems within southeastern Australia. More than 8000 hygrothermal and bio-hygrothermal simulations were completed to evaluate seasonal moisture patterns and calculate mould growth potential for nine typical external wall systems. Results reveal that the combination of increased thermal insulation and air-tightness measures between the 2010 and 2022 specified building envelope energy efficiency regulations further increased predicted Mould Index values, particularly in cool-temperate climates. This was in part due to insufficient moisture management requirements, like an air space between the cladding and the weather resistive layer and/or the low-water vapour permeability of exterior weather resistive pliable membranes. By contrast, warmer temperate climates and drier cool-temperate climates exhibit consistently lower calculated Mould Index values. Despite the 2022 requirement for a greater water vapour-permeance of exterior pliable membranes, the external walls systems explored in this research had a higher calculated Mould Index than the 2010 regulatory compliant external wall systems. Lower air change rates significantly increased calculated interstitial mould growth risk, while the use of interior vapour control membranes proved effective in its mitigation for most external wall systems. The addition of ventilated cavity in combination with either or both an interior vapour control membrane and a highly vapour-permeable exterior pliable membranes further reduced risk. The findings underscore the need for tailored, climate-responsive design interventions to minimise surface and interstitial mould growth risk and building durability, whilst achieving high performance external wall systems. Full article

The Yungang Grottoes are undergoing degradation by weather and environmental erosion. Here, we propose a natural ventilation strategy to optimize the environments in Cave 9 and Cave 10 of the Yungang Grottoes. The novelty of this work is to use an effective computational fluid dynamics (CFD) simulation and a hybrid of the beetle antennae search and particle swarm optimization algorithms (BAS–PSO) to determine which natural ventilation scenario yields the maximum total heat transfer rate (Q_max). A CFD hygrothermal model is first developed and shows high precision in predicting temperature and humidity conditions based on real-time measured data. The natural ventilation efficiency is enhanced by different configurations of doors and windows with four ventilation rates. Combined with eXtreme Gradient Boosting (XGBoost) fitting, the hybrid BAS–PSO algorithm yields the largest Q_max (5746.74 W), which is further confirmed by CFD simulations with the outcome of a comparable Q_max (5730.67 W). It indicates that the hybrid algorithm exhibits a good performance in the identification of optimal configurations. The effectiveness of the proposed natural ventilation strategy is verified by on-site measured data. Our findings provide an effective natural ventilation strategy that is beneficial to the energy-efficient preservation of the Yungang Grottoes. Full article

Earth materials are recognized for their excellent thermal and hygrothermal properties but exhibit low mechanical resistance. Binder stabilization improves compressive strength but often increases the carbon footprint. This study evaluates the mechanical, thermal, hygrothermal, and environmental properties of 12 stabilized earth concrete formulations. The samples were prepared using four types of excavated earths (A, B, C, and D) with varying granular distributions and chemical compositions, stabilized with three industrial binders: two low-carbon activated GGBS-based binders (LN and LW) and a CEM II cement. The samples were cured at 20 °C and 100% relative humidity. Density, porosity, thermal conductivity, specific heat capacity, and Moisture Buffer Value (MBV) were measured at 28 days of curing, using standard methods from concrete and geotechnical fields, while compressive strength tests were performed at 7, 28, and 90 days. The results revealed that gravel-rich earths (A and B) demonstrated higher densities and compressive strengths compared to fine-rich earths (C and D). GGBS-stabilized earths exhibited superior mechanical performance (1.7–14.8 MPa) compared to cement-stabilized earths (0.8–3.8 MPa). Despite low binder content (7%), thermal and hygrothermal properties were largely influenced by the earth’s composition. Thermal conductivity (0.48–0.59 W·m⁻¹·K⁻¹), volumetric heat capacity (1661–2031 J·m⁻³·K⁻¹), and MBV (0.9–1.9 g·m⁻²·%RH⁻¹) were consistent with raw earth values, supporting thermal inertia and humidity regulation. The carbon footprint analysis showed that both LN and LW binders had the lowest emissions (29–34 kg CO₂·eq/m³), with LN binders demonstrating consistent normalized performance (5.2–6.2 kg CO₂·eq/m³·/MPa) and LW binders exhibiting superior mechanical performance and a lower normalized indicator (2.3–5.4 kg CO₂·eq/m³/MPa). Conversely, CEM II-stabilized formulations displayed the highest emissions (70–86 kg CO₂·eq/m³) and the least favorable compressive strength-to-carbon ratios. These findings emphasize the potential of stabilized earth concretes, particularly those with low-carbon GGBS binders, for sustainable and energy-efficient construction practices. Full article