Search Results (43)

Wind-driven rain (WDR) is recognized as a primary source of moisture intrusion in exterior wall assemblies. However, China’s national code for thermal design of wall assemblies predominantly relies on temperature criteria classified by thermal zones, with humidity-related impacts on building thermal performance remaining unconsidered. Thus, the influence of WDR on the hygrothermal performance of exterior wall assemblies necessitates systematic investigation. This study aims to explore variations in moisture resistance among different wall assemblies under WDR exposure and differences in hygrothermal performance of identical assemblies across designated thermal zones. To this end, the hygrothermal behavior of five typical insulated wall assembly types was evaluated across 21 representative cities spanning four major thermal zones in China. Results indicate significant disparities in the hygrothermal performance of wall assemblies under WDR across thermal zones: dryness rates decreased by an average of 100%, 93.33%, 44%, and 30% in Severe Cold, Cold, Hot Summer and Cold Winter, and Hot Summer and Warm Winter Zones, respectively. Furthermore, although certain wall assemblies eventually dried over time, the risk of mold growth persisted. Notably, wall assemblies with external EPS insulation exhibited high sensitivity to WDR, while self-insulated and internal insulation systems were also vulnerable to WDR in the Hot Summer and Warm Winter Zone. In conclusion, annual WDR exposure and U-value are key factors in designing wall assemblies for optimal hygrothermal performance. 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

Reflective materials, characterized by high albedo and thermal emissivity, offer effective passive cooling strategies for reducing building energy demand. While prior studies have developed thermal transfer models validated under laboratory conditions or conducted short-term monitoring in non-air-conditioned spaces, their effectiveness in operational buildings remains underexplored. This research evaluates the change in cooling energy demand and indoor thermal comfort in a retrofitted office building with reflective materials in China’s Hot Summer and Cold Winter (HSCW) zone. The calibrated WUFI^®Plus simulations show that the application of reflective roof and window materials can result in an 11.3% reduction in cooling energy demand. Moreover, occupant surveys indicate improved thermal perception, with the mean Thermal Comfort Vote (TCV) rising from −0.75 to −0.30, thermal acceptability increasing from 0.10 to 0.35, and 80% of occupants reporting cooler conditions. These subjective results align with simulated Predicted Mean Vote (PMV) reductions (0.82 → 0.74), confirming the retrofit’s effectiveness. While the energy savings are more modest than those reported in Mediterranean climates, they are generally consistent with the energy saving ratios of buildings in the HSCW region as evaluated by previous studies. This study provides a framework for assessing retrofits in occupied buildings with reflective materials and indicates the practicality of such retrofits as an economic, low-disruption strategy for upgrading aging office building stocks in the HSCW zone. Full article

The article concerns the internal insulation of a utility room located in the attic of a building from the late 1990s. Due to the freezing of the external wall, an analysis of heat flow through this wall was conducted. Various insulation materials recommended for internal application were tested: EPS and resol board (100 mm thick) and an aerogel mat (10 mm thick). The analyses included the temperature distribution in the wall and indoor thermal conditions. Experimental studies determined the thermal conductivity coefficient (λ) of the selected insulation materials and the heat transfer coefficient for the analyzed wall. Numerical analyses were conducted with the TRISCO 12.0w software, which applies the finite element method (FEM), whereas the assessment of interlayer condensation risk was performed using the WUFI^® Pro 5.1 program. Full article

A wave of energy efficiency-focused activity has spread across Europe in recent years, with ambitious goals for improving the energy performance of existing buildings through various directives. Among these existing buildings, there are older structures with heritage-protected facades. Some of the protected facades consist of timber plank frame walls, which were common in Norway in the 19th and early 20th centuries. Internal insulation is an option for increasing the energy efficiency of such walls while preserving their protected facades. However, this approach alters the moisture performance of the wall and introduces a potential risk for mould growth, which must be assessed. To better understand the performance of these walls, the $s_d$ values of traditional types of building paper have been tested, as timber plank frame walls comprise vertical planks covered in building paper. In addition, the risk of mould growth in timber plank frame walls has been evaluated using the one-dimensional simulation tool WUFI^® Pro by modelling the wall with internal retrofitting and varying input parameters. The types of building paper used have a wide range of vapour resistance values (diffusion-equivalent air layer thicknesses, $s_d$ values), which range from 0.008 m to 5.293 m. Adding 50 mm of interior insulation generally resulted in a low risk of mould growth, except in cases involving the use of a moisture-adaptive vapour barrier (MAVB). The MAVB did not result in an acceptable mould growth risk in any of the tested scenarios. Full article

In response to concerns over resource shortages and environmental impacts, biobased materials are increasing in popularity. This includes an interest in replacing traditional vapour control systems, including polyethene (PE) membranes. However, the susceptibility of these materials to moisture-related degradation poses challenges. This study examines the water vapour diffusion resistance of the vapour retarder and the wind shield as key properties. Examining wood frame walls designed with low water vapour diffusion resistance wind shields, this study analyses the necessary properties of the vapour retarder as a function of the properties of the wind shield. We evaluated exterior wood frame walls that were thermally insulated with materials including mineral wool and biobased options such as flax, grass, wood fibre, straw, and cellulose. Using WUFI Pro software, we determined the relations between properties necessary to prevent mould growth. Hygrothermal simulations determined the necessary properties of the vapour retarder as a function of the properties of the wind shield. Analyses were carried out in temperate cold climates. Wind shield diffusion tightnesses ranging from 0.01 to 1 (m²·s·GPa)/kg were evaluated. Assessments were performed for walls with a U-value of 0.15 and 0.10 W/(m²·K). The indoor humidity classes 1 to 3, as defined in EN ISO 13788, were used for the simulations. The results indicate that the necessary properties of the vapour retarder depend on the properties of the wind shield, as well as the insulation material, the indoor humidity, and the U-value. As the wind shield diffusion tightness decreases, the necessary vapour retarder diffusion tightness also decreases, eventually reaching a fixed value determined by the insulation material, the indoor humidity, and the U-value. Full article

This paper examines the water-vapour diffusion resistance (Z-value) of vapour versus wind barriers by determining their Z-value ratio in exterior wood-frame walls thermally insulated with six different materials to prevent mould growth. Using WUFI Pro, the water-vapour diffusion resistance requirements were determined for thermal insulation using mineral wool and biogenic materials: wood fibre, straw, flax, grass, and hemp. Hygrothermal simulations determine the minimum Z-value ratio between these materials with vapour versus wind barriers in temperate and cold climates. Wind barriers with Z-values between 1 and 8 GPa s m²/kg were used in walls with U-values of 0.15 and 0.10 W/m² K. The indoor moisture load was defined from classes of 1 to 5 with a U-value of 0.15 W/m² K and classes of 2 and 3 were used for a U-value of 0.10 W/m² K. The Z-value ratio depends on the Z-values of the wind barrier and thermal insulation material, moisture load class, and U-value. The required Z-value ratio declines with an increased wind-barrier Z-value. The vapour-barrier Z-value approaches a fixed threshold for wind-barrier Z-values approaching lower values (1 GPa s m²/kg) and those approaching higher values (8 GPa s m²/kg), depending on the thermal insulation material. This parameter study examines wind barriers with a Z-value ranging between 1 and 8 GPa s m²/kg, which characterises typical wind barriers used in Denmark For the water-vapour diffusion resistance requirement of the vapour barrier, the Z-value increases for increased moisture load classes and thermally insulated walls with lower U-values. The conversion between the Z-value, the Sd-value, and the water-vapour resistance factor µ can be found in DS/EN ISO 12572:2016. Full article

One of the technical solutions to improve indoor thermal comfort and reduce energy consumption in buildings is the use of demand-controlled ventilation (DCV) systems. The choice of the control method becomes more important when the walls in the room are finished with moisture-buffering materials. This study explores the impact of four DCV system control scenarios (control of temperature, relative humidity, and carbon dioxide concentration for two different supply airflows to the room) combined with various indoor moisture-buffering materials (gypsum board and cement–lime plaster) on the variability of indoor air quality parameters, thermal comfort, and energy. The analysis was performed by computer simulation using WUFI Plus v.3.1.0.3 software for whole-building hydrothermal analysis. Control-based systems that maintain appropriate relative humidity levels were found to be the most favourable for localised comfort and were more effective in terms of energy consumption for heating and cooling without humidification and dehumidification. This research also revealed that the moisture-buffering effect of finishing materials can passively contribute to enhancing indoor air quality, regardless of the room’s purpose. However, higher energy consumption for heating was observed for better moisture-buffering materials. Full article

Increasing climate fluctuations and extremes due to climate change are particularly concerning for wooden building envelopes, especially in the Nordic region, which has harsh climatic conditions. The exterior coating’s barrier properties are crucial for maintaining building envelopes’ intended lifespans. Hence, it is unfortunate that the vapor resistance of exterior coatings is not openly accessed for commercial products. This study investigates the influence of the water vapour resistance of exterior coatings on the moisture conditions and mould growth risk of ventilated wooden claddings. The $s_d$-value (vapour diffusion-equivalent air layer thickness) is determined for nine free-standing coatings (alkyds, emulsions, and acrylics); in total, 100 specimens are tested with the wet cup method. Additionally, with WUFI Pro, one-dimensional hygrothermal simulations under Nordic climatic conditions investigate how the coatings’ vapour resistance might influence the moisture dynamics of wood. The mould risk is assessed by the add-on WUFI VTT Model. The determined $s_d$-values for the coatings range from 0.453 to 1.350 m (three layers) and from 0.690 to 2.250 m (six layers), showing a strong correlation with the dry film thickness. The vapour resistance of the coatings does not significantly influence the wood moisture content, but lower resistance may cause slightly faster drying. The importance of surface treatment is confirmed. The mould risk is notably higher in a Stavanger climate on a southwest-facing wall compared to Trondheim on a north-facing wall. Full article

The residential sector of existing buildings has great potential in energy savings and the improvement of indoor conditions. The modernization of buildings is of particular concern to the policies of the European Union, local governments, and building users. The aim of this paper is to present an analysis of indoor parameters and energy consumption for heating for an apartment located in a pre-war tenement building before and after thermomodernization. The analysis was conducted for winter conditions and was based on measurements and simulations. Originally, the building had not undergone any thermomodernization actions since its reconstruction after WWII. Interior, exterior, and surface temperatures were recorded to describe the thermal conditions of the apartment, while gas meter readings were used to estimate energy consumption for heating purposes. WUFI Plus software (v.3.2.0.1) was used to estimate energy consumption and perform energy simulations for the apartment over an extended period of time. The best thermomodernization effect resulted from the replacement of windows and the inefficient heating system, avoiding surface condensation and reducing final energy consumption by more than 50%. The extended options resulted in energy savings higher than 70%. The presented analysis shows the importance of retrofit measures and proves that even a small improvement can bring significant benefits. Full article

The search for environmentally friendly and low-carbon-footprint construction materials continues progressively. Researchers are now interested in innovative materials that connect with the principles of sustainable construction, and materials such as hemp concrete prove to be promising. This article presents the results of a study that aimed to evaluate the hygrothermal performance of hemp concrete integrated into the building envelope using the hygrothermal tool WUFI Pro 6.2. The simulation model was compared and verified with existing models before its utilization for this study. The results of this verification were in good agreement, which gave us more confidence in its application for further parametric studies of building envelopes in hot climate zones. Three wall systems were simulated: (i) a wall system with hemp concrete, (ii) a compressed earth block wall, and (iii) a cement block wall. The most important variables used in the simulations were the hygrothermal properties of the materials or wall components and the incident solar radiation. The simulation results showed that hemp concrete has good thermal performance and temperature and humidity regulation capabilities of the building envelope. The interior surface temperatures of the hemp concrete walls were between 22.1 °C and 24.6 °C compared to the compressed earth block and cement block walls, where the surface temperatures were between 22.0 °C and 27 °C and between 21.2 °C and 28.7 °C, respectively, and between 23 °C and 45 °C for the exterior temperatures. These values remain the same with the increase in exterior temperatures for hemp concrete walls. In conclusion, hemp concrete could be a great alternative material for use in construction for hot climate zones. Full article

Buildings located in extreme cold climates encounter challenges (e.g., heat loss, condensation, and frozen utilities), especially within their wall envelopes. These challenges also play a pivotal role in occupant health, comfort, and the structural integrity of the building. While the existing literature has primarily focused on thermal performance, this study underscores the importance of evaluating hygrothermal performance within wall envelopes, given the existence of mold growth even in cases of high thermal resistance. Therefore, the aim of this study was to evaluate the hygrothermal performance of an adaptable house wall (AHW) panel that incorporates composite infill panels paired with vacuum-insulated panels to endure harsh cold conditions in Alaska. Therefore, three steps were proposed to: (1) collect the material and thermal properties of the AHW; (2) model the hygrothermal performance of the AHW in WUFI^® PRO v6.7 software; and (3) analyze the results. The results revealed a moderate risk of mold growth in the inner plywood layer of the AHW, whereas the outer plywood layer showed zero risk, indicating an acceptable condition. The findings aid decisionmakers in recognizing potential mold-related issues in building walls before advancing to the construction phase. Full article

Smart vapour barriers enable building envelopes to dry toward the interior side. This property can be used in compact wooden roofs to create more slender structures by placing the wooden load-bearing elements inside the insulation layer. There is, however, some concern that the ceiling assembly on the interior side may inhibit inward drying by trapping moisture between the vapour barrier and the ceiling boards. This article examined the water vapour resistance of gypsum boards painted with two, four, and six layers of typical ceiling paints. WUFI^® 2D simulations were conducted to assess the risk of mould growth in compact wooden roofs with painted board ceilings. It was found that a painted ceiling board may exhibit an equivalent stagnant air layer thickness (s_d value) between 0.074 m for two layers of the most vapour-open paint and 0.53 m for six layers of the least vapour-open. For an unpainted board, the s_d value was measured to be 0.071 m. The difference was not found to make a substantial impact on the drying of a typical compact wooden roof. The application of paint may cause the assembly to dry at a slightly slower rate but was not found to present a notably higher risk of mould growth, even under unfavourable conditions. Full article

Laminated bamboo lumber (BLL) and bamboo scrimber (BS) are potential environmentally friendly building materials, considering that they are hygroscopic materials and that their hygrothermal performance is closely related to the occupants’ comfort, their building durability, and building energy consumption. This study carried out material property tests on bamboo-based materials (BLL and BS) and analyzed hygrothermal performance simulations on bamboo exterior wall constructions in five major climatic zones using WUFI. Results show that BS had a greater heat storage capacity than BLL. However, BLL showed a relatively higher moisture sorption capacity, and BLL was more easily permeated by vapor than BS. The water content (WC) of 12 walls of BLL and BS was below 20%. BLL and BS met the requirements of the envelope, and the WC of BS was lower than that of BLL. Based on the results, the walls designed in this study are suitable for the corresponding climate zones. In the cold and severe climate zones especially, the external insulation system walls performed better than the internal insulation system. The external insulation system was recommended for these two climate zones. The design and simulation results of walls made of two types of bamboo-based materials provide a scientific basis for the application of the material. Full article

With the introduction of energy-efficient buildings, the importance of embodied energy in new buildings has become increasingly relevant to minimising the impact of climate change. This study compares two existing four-storey residential buildings: one building has a reinforced concrete (RC) structure and the other has a timber structure. The study’s aim is to find out which building components are responsible for the largest embodied impacts and whether there are differences between the two construction methods. The specificity of the wooden building is the combined use of solid and lightweight timber elements. The methodology consists of a general life cycle assessment (LCA) and a more detailed analysis of the product stage using the eco2soft software. The heating and cooling energy demand was calculated using the WUFI Plus software with recent regional climate data sets. The results show that for both types of construction in multi-storey buildings, it is not only the superstructure that needs to be considered, but also the floor structures, which have a major influence on the embodied impact. The timber building requires less energy to maintain the indoor climate within the set temperatures. As climate change has progressed rapidly in Austria in recent years, it is recommended that the standards for climate models be updated more quickly to allow realistic prediction of thermal comfort at the design stage. Full article