Radiative Heat Gain Research Articles

Assessing impact of urban densification on outdoor microclimate and thermal comfort using ENVI-met simulations for Combined Spatial-Climatic Design (CSCD) approach

Future urban planning requires context-specific integration of spatial design and microclimate especially for tropical cities with extreme weather conditions. Thus, we propose a Combined Spatial-Climatic Design approach to assess impact of urban densification on annual outdoor thermal comfort performance employing ENVI-met simulations for Singapore. We first consider building bylaws and residential site guidelines to develop eight urban-density site options for a target population range. We further classify annual weather data into seven weather-types and use them as boundary conditions for the simulations. Comparing such fifty-six combined spatial-climatic simulation outputs by analyzing Outdoor Thermal Comfort Autonomy, we report the influence of site geometry is nominal on air temperatures but significant for Mean Radiant Temperatures and Physiological Equivalent Temperatures. Neighborhoods with taller (20 % increase in mean height) buildings and narrower footprints exhibit better thermal performance compared to short and wider (12–58 % decrease in mean width) buildings, due to less radiative heat gain during solar noon. For a high density tropical urban context, like Singapore with high sun angle and solar radiation, mutual shading and presence of wind enhances thermal comfort. Results provide useful and actionable recommendations on ideal building profile for heat responsive neighborhoods in low-latitude hot-humid cities similar to Singapore.

Implications of heat exchange for a free-living endangered marsupial determined by non-invasive thermal imaging.

We used thermal imagining and heat balance modelling to examine the thermal ecology of wild mammals, using the diurnal marsupial numbat (Myrmecobius fasciatus) as a model. Body surface temperature was measured using infra-red thermography at environmental wet and dry bulb temperatures of 11.7-29°C and 16.4-49.3°C, respectively; surface temperature varied for different body parts and with environmental temperature. Radiative and convective heat exchange varied markedly with environmental conditions and for various body surfaces reflecting their shapes, surface areas and projected areas. Both the anterior and posterior dorsolateral body areas functioned as thermal windows. Numbats in the shade had lower rates of solar radiative heat gain but non-solar avenues for radiative heat gain were substantial. Radiative gain was higher for black and lower for white stripes, but overall, the stripes had no thermal role. Total heat gain was generally positive (<4 to >20W) and often greatly exceeded metabolic heat production (3-6W). Our heat balance model indicates that high environmental heat loads limit foraging in open areas to as little as 10min and that climate change may extend periods of inactivity, with implications for future conservation and management. We conclude that non-invasive thermal imaging is informative for modelling heat balance of free-living mammals.

Experimental investigation of indoor lighting/thermal environment of liquid-filled energy-saving windows

To enhance the effectiveness of energy-saving buildings, windows play a crucial role, as they contribute to comfort, energy efficiency, and adaptability. However, traditional static windows, which primarily focus on reducing solar radiation, struggle to strike a balance between heating/cooling requirements during winter and summer seasons. On the other hand, dynamic windows, while offering adjustability, suffer from issues such as high haze and poor color rendering, making them less suitable for residential buildings. In this study, we propose a novel reversible liquid-filled energy-saving window that effectively regulates indoor solar radiation heat gain. To evaluate the dynamic indoor light/heat environment provided by liquid-filled energy-saving windows, we conduct an experimental investigation. Results indicate that windows filled with 10 wt% and 20 wt% CuSO4 solution cause a 1.5 °C and 2.5 °C reduction in indoor mean air temperature compared to water-filled windows during the summer season. Similarly, in the winter season, the decrease is 1.4 °C and 0.5 °C, respectively. Moreover, there is no significant difference in indoor illuminance between energy-saving windows filled with 10 wt% and 20 wt% CuSO4 solution. With the mass concentration of 10%wt CuSO4 solution, indoor mean illuminance difference between the two groups is only 236 lux and 214 lux during the summer and winter seasons, respectively.

New solar radiation transmittance models of transparent envelope based on spectral splitting and their influence on building heat gain

Climate change and the energy crisis have led to increasing attention to building energy efficiency worldwide, and transparent envelopes are more critical as a weak link in building energy efficiency. However, there is a lack of quantitative research on the spectral transmittance properties of transparent envelopes. In this paper, the spectral transmittance of transparent envelopes is quantitatively studied using the controlled variable method. The transmittance calculation formula in the existing standard is modified. Firstly, five types of transparent envelopes commonly used are selected, and their transmittance to the full solar spectrum is studied to establish a transmittance model for different wavelengths. The study also focuses on the 300 nm–1100nm waveband and establishes a solar radiation transmittance benchmark model (SRTB model) based on single-pane clear glass. Secondly, the solar radiation transmittance at different wavelengths is tested by considering both the glass material and the inclination angle, and a solar radiation transmittance modified model (SRTM model) that can be modified to the SRTB model is established. Thirdly, the variation between the incident angle and transmittance is investigated, and the solar radiation transmittance-incident angle model (SRT - IA model) is developed. The results show that deviations between the fixed transmittance and SRT - IA model can reach a maximum of more than 10% for incident angles of less than 60°. Finally, the variation in radiation heat gain due to the SRT - IA model and fixed transmittance is compared in China based on typical meteorological year data. The research conclusion can provide a more precise assessment of the building heat gain from transparent envelopes and then evaluate the building energy consumption reasonably, and provide a theoretical basis for the full-spectrum utilization efficiency of solar radiation.

Characteristics of Marine Heatwaves in the Indonesian Waters during the PDO, ENSO, and IOD Phases and Their Relationships to Net Surface Heat Flux

We conducted an investigation into the characteristics of marine heatwaves (MHWs) in Indonesian waters, aiming to understand the underlying mechanisms responsible for their formation, particularly the ones generated by net surface heat flux. To accomplish this, we utilized remote sensing data from the National Oceanic and Atmospheric Administration and the European Centre for Medium-Range Weather Forecasts. The dataset covered a 40-year period (1982–2021) encompassing both warm (1982–2007) and cold (2008–2021) phases of the Pacific Decadal Oscillation (PDO). Statistical analysis methods were employed to process the data. Our study reveals significant findings regarding MHWs in Indonesian waters. We observed the highest average frequency and maximum intensity of MHWs, occurring approximately 2–3 times a year and exceeding 1.5 °C, respectively, during the warm phase of PDO (with El Niño events occurring more frequently than La Niña). Conversely, the longest durations of MHWs in Indonesian waters were recorded during the cold phase of PDO (with La Niña events occurring more frequently than El Niño), spanning approximately 7–15 days. We identified local forcing in the form of net surface heat flux as the primary driver of MHW frequency and maximum intensity. During the warm phase of PDO, the net surface heat flux was notably higher, primarily due to increased shortwave radiation (heat gain) and reduced latent heat flux (heat loss) through the evaporation process. These factors collectively contributed to maintaining warmer ocean temperatures. Moreover, our study provides valuable insights into the interannual variability of MHWs through the application of composite calculations. We discovered a strong correlation between the occurrence of El Niño and positive Indian Ocean Dipole (IOD) events during the warm PDO phase and the highest frequency and maximum intensity of MHWs, with approximately 2.52 events and 1.54 °C, respectively. In contrast, we found that MHWs with the longest durations were closely linked to La Niña and negative IOD events during the cold PDO phase, lasting approximately 10.90 days. These findings highlight the complex interplay between climate phenomena and MHW characteristics, further deepening our understanding of their dynamics.

Characteristics of office lighting energy consumption and its impact on air conditioning energy consumption

The energy consumption of office buildings has increased sharply since the 21st century with the increasing urbanization coverage. At this stage, the energy consumption of office buildings in China mainly comes from air conditioning and lighting. This paper obtains the regression equation of natural lighting illumination and radiant heat gain under different curtain conditions through experiments and simulations, and gives the theoretical calculation process of curtain regulation of office thermal and light environment and energy consumption. DeST and Ecotect software were used to analyze the thermal and light environment and energy consumption of the office. The results show that setting curtains in the room can effectively improve the indoor thermal light environment, the higher the transmittance of curtains the lower the lighting energy consumption, the higher the number of high temperature hours of natural room temperature and the greater the radiant heat gain. The room with thick curtains has the lowest energy consumption for air conditioning in summer, followed by the room with thin curtains, and the room without curtains has the highest energy consumption for air conditioning. The room without curtains has the lowest energy consumption for artificial lighting, the room with thin curtains has the second lowest, and the room with thick curtains has the highest electricity consumption for artificial lighting. The air conditioning energy consumption accounts for the main building energy consumption, followed by the lighting energy consumption. After setting curtains in the office, the air conditioning energy consumption caused by the solar radiation heat entering the room through the exterior windows is smaller than the lighting energy consumption caused by artificial lighting. Therefore, the installation of internal shading with moderate transmittance and good thermal insulation performance can make the energy saving of lighting and air conditioning energy consumption reach the optimal value.

Individual reflectance of solar radiation confers a thermoregulatory benefit to dimorphic males bees (Centris pallida) using distinct microclimates.

Incoming solar radiation (wavelengths 290-2500 nm) significantly affects an organism's thermal balance via radiative heat gain. Species adapted to different environments can differ in solar reflectance profiles. We hypothesized that conspecific individuals using thermally distinct microhabitats to engage in fitness-relevant behaviors would show intraspecific differences in reflectance: we predicted individuals that use hot microclimates (where radiative heat gain represents a greater thermoregulatory challenge) would be more reflective across the entire solar spectrum than those using cooler microclimates. Differences in near-infrared (NIR) reflectance (700-2500 nm) are strongly indicative of thermoregulatory adaptation as, unlike differences in visible reflectance (400-700 nm), they are not perceived by ecological or social partners. We tested these predictions in male Centris pallida (Hymenoptera: Apidae) bees from the Sonoran Desert. Male C. pallida use alternative reproductive tactics that are associated with distinct microclimates: Large-morph males, with paler visible coloration, behave in an extremely hot microclimate close to the ground, while small-morph males, with a dark brown dorsal coloration, frequently use cooler microclimates above the ground near vegetation. We found that large-morph males had higher reflectance of solar radiation (UV through NIR) resulting in lower solar absorption coefficients. This thermoregulatory adaptation was specific to the dorsal surface, and produced by differences in hair, not cuticle, characteristics. Our results showed that intraspecific variation in behavior, particular in relation to microclimate use, can generate unique thermal adaptations that changes the reflectance of shortwave radiation among individuals within the same population.

Assessment of the dynamic thermal behaviour of a test room using computer simulations and experimental measurements

People spend most of the time indoors and adequate comfort level in buildings is fundamental for their well-being and productivity. These issues can be investigated using both simulation models and experimental measurements in dedicated laboratories or in real buildings. The numerical and experimental approaches need to be combined in order to overcome the limitations of each one. This paper presents the application of a detailed numerical model to the CORE-CARE laboratory built at the University of Padua, a test room employed for indoor environmental quality (IEQ) evaluations. The HVAC plant consists of a mechanical ventilation unit and radiant systems for space heating and cooling. Each radiant surface presents different constructive characteristics and can operate independently. The test room is a novelty in this panorama, as it was integrated in an existing building, as a room for regular use. The impossibility of controlling external disturbances makes the dynamic modelling of the room extremely important, for the laboratory control and knowledge. For this reason, the test room behaviour in response to different HVAC system settings and external disturbances is analysed. Two experimental campaigns were carried out both in the heating and cooling seasons, activating one surface at a time, in order to both validate the model and set-up the transient thermal behaviour of the laboratory. In summer, three experimental set-ups were arranged: closed blinds, opened blinds and presence of a thermal dummy. The data analysis highlights that the North surface exhibits the fastest response in both seasons, whereas the floor is the slowest due to its inertia. In summer, the active surface equilibrium temperature is closer to the water supply temperature for responsive and massive surfaces, and it rises with incoming solar radiation and thermal dummy heat gain. The cooled floor enhances the space's thermal stratification. Simulation results show that the model reproduces the system's real dynamics, with a maximum RMSE of 2.3 and 1.9 °C for the North surface and air temperature.

Thermal regulation mechanism of air-drying shelter to indoor environment of earth buildings located in Turpan basin with extremely dry and hot climate conditions

This study investigates the thermal regulation mechanism of air-drying shelter of earth buildings located in Turpan basin to indoor thermal environment under the extremely dry and hot climate condition. Firstly, a field measurement lasting for three days was performed to investigate the thermal effect of air-drying shelter on indoor thermal condition. The measured results indicated that air-drying shelter provides the shaded space and natural ventilation to reduce the internal surface temperature of the roof and further improve the indoor thermal comfort in the hot summer. Then, a series of numerical studies on the effects of design parameters of air-drying shelter on indoor environment of earth building in Turpan basin were performed. The selected design parameters of air-drying shelter included air-drying shelter to room height ratio, thickness of carved walls, thickness of air-drying shelter's roof and hole to wall area ratio. The simulated results demonstrated that hole to wall area ratio of the carved walls is considered as an important design parameter of air-drying shelter, and increasing hole to wall area ratio of carved walls could increase solar radiation heat gain of roof, leading to increasing internal surface temperature of roof and indoor air temperature.

Production of light-coloured, low heat-absorbing Holstein Friesian cattle by precise embryo-mediated genome editing

Context Genome editing enables the introduction of beneficial sequence variants into the genomes of animals with high genetic merit in a single generation. This can be achieved by introducing variants into primary cells followed by producing a live animal from these cells by somatic cell nuclear transfer cloning. The latter step is associated with low efficiencies and developmental problems due to incorrect reprogramming of the donor cells, causing animal welfare concerns. Direct editing of fertilised one-cell embryos could circumvent this issue and might better integrate with genetic improvement strategies implemented by the industry. Methods In vitro fertilised zygotes were injected with TALEN editors and repair template to introduce a known coat colour dilution mutation in the PMEL gene. Embryo biopsies of injected embryos were screened by polymerase chain reaction and sequencing for intended biallelic edits before transferring verified embryos into recipients for development to term. Calves were genotyped and their coats scanned with visible and hyperspectral cameras to assess thermal energy absorption. Key results Multiple non-mosaic calves with precision edited genotypes were produced, including calves from high genetic merit parents. Compared to controls, the edited calves showed a strong coat colour dilution which was associated with lower thermal energy absorbance. Conclusions Although biopsy screening was not absolutely accurate, non-mosaic, precisely edited calves can be readily produced by embryo-mediated editing. The lighter coat colouring caused by the PMEL mutation can lower radiative heat gain which might help to reduce heat stress. Implications The study validates putative causative sequence variants to rapidly adapt grazing cattle to changing environmental conditions.

Characteristics of Marine Heatwaves (2008–2021) in the Savu Sea, East Nusa Tenggara

In this paper, we investigate the characteristics and the mechanism underlying the formation of marine heatwaves (MHWs) in the Savu Sea, known as the richest marine biodiversity area in the world. The focus is on identifying the frequency, intensity, and duration of occurrence MHWs generated by local forcing in the form of net surface heat flux. The study utilizes the remote sensing data from NOAA Optimum Interpolation (OI) Sea Surface Temperature (SST) for SST and The European Centre for Medium-Range Weather Forecasts Reanalysis v5 (ERA-5) for net surface heat flux components (shortwave radiation, longwave radiation, sensible heat flux, and latent heat flux). All data covers the period for the last 14 years (2008–2021) during the cold phase of the Pacific Decadal Oscillation (PDO) and then processed by statistical analysis methods. The results showed that the mean frequency, intensity, and duration of occurrence MHWs in the Savu Sea were around two times a year, 1.4–1.6 °C, and 10–12 days, respectively. The highest frequency and intensity MHWs occurred at around 122–124 °E and 8.30–9.30 °S (northern Savu Sea) generated by the most significant net surface heat flux in these areas. This study reveals the most dominant contribution of net surface heat flux in the northern Savu Sea comes from high shortwave radiation (heat gain) and low latent heat flux through the evaporation process (heat loss), thus keeping the ocean warm.

Influence of Surface Emissivity of Target Environment on Whole Heat Transfer of Porous Ceramics Radiant Burner

The heat transfer between a porous ceramic radiant burner (PCRB) and a target environment was studied. The black aluminum pot (BAP) and white aluminum pot (WAP) with an emissivity of 0.72 and 0.22 were experimentally used to obtain the temperature distribution and thermal efficiency of a burner. Under the same heat load, the porous ceramic plate (PCP) of WAP is 79~90 °C higher than BAP, but the measured thermal efficiency of BAP is 15~20% higher than WAP. A heat transfer model for PCRB and pots was established based on the radiant and convection heat transfer theories. This model is applicable to common infrared radiant burners. The heat gain type of the pot was analyzed quantitively, with a relative error of less than 7%. The influence of the pot surface emissivity on the burner and heat transfer change of the pot was discussed, and the solid radiation heat gain of BAP is approximately double that of BAP under the same heat load. For PCRBs whose main heat is from radiation, the pot with a high surface emissivity can achieve better radiation utilization to improve thermal efficiency.

An evidence-based framework for designing urban green infrastructure morphology to reduce urban building energy use in a hot-humid climate

Urban green infrastructures (UGIs) play an essential role in reducing urban building energy consumption by cooling surrounding areas and shielding buildings from direct solar radiation heat gain. Although the energy-saving effect of UGIs is widely agreed upon, there is a lack of systematic knowledge about how UGI morphology affects urban building energy consumption. Consequently, an effective method to design UGI morphology to reduce urban building energy consumption in urban design is not available. A grading system was proposed to evaluate the strength of evidence for the findings and conclusions in studies that pertain to the cooling and energy-saving effects of UGI. The evidence-based literature review found that strategically designing the morphology of UGI, including its size, shape, location, connectivity, spatial pattern, and configuration, can effectively reduce the air temperature surrounding the UGI area and building energy demand. This study formulated a morphological design framework for UGI as part of the urban design process to reduce urban building energy consumption. Based on the evidence-based answers to the key questions in the framework, design strategies are provided as visual charts and technical principles. The study includes an urban design case in Nanjing, China, which applied this framework to achieve the goal of urban energy savings.

Comparing thermal performance of standard humanitarian tents

Humanitarian tents provide emergency shelter for people displaced by conflict and disaster in diverse climatic conditions. This article compares the thermal performance of two standard humanitarian tents – the Standard Family Tent (SFT) and the Geodesic Family Tent (GFT). The SFT is the most widely used humanitarian shelter, while the GFT was recently introduced as a potential replacement intended to provide, inter-alia, improved thermal performance. The study aims to assess the extent to which this intention is achieved and, in doing so, improve understanding about how tent material and morphology affect thermal performance. Several variables, including internal air temperature, surface temperature, relative humidity and air change rates, were measured and compared in hot and cold conditions. Results demonstrate that the GFT performs better than the SFT regarding radiant heat gain, conductive heat loss and increased air tightness. However, performance of the GFT in relation to heat gain and heat loss is similar to that of the SFT with an additional shade net. Other functional advantages of the GFT are improved structural stability and spaciousness, which, together with improved thermal performance, suggest this marginal innovation in shelter design can positively impact emergency shelter living conditions.

A numerical investigation of energy-saving potential of inner solarshade film: A case study of the National Aquatics Center, China

Transparent or semitransparent roof structures of sports venues have attracted much architect's attention, but the energy consumption of these buildings must be considered as a crucial aspect too. For the 2022 Beijing Winter Olympics games, the curling sports event will be held in the China's National Aquatics Center. The roof of this center is made of double-layer ETFE film (Ethylene-tetra-fluoro-ethylene, a semitransparent film), which allows a large amount of external solar radiation to enter the main sports hall, leading to huge cooling demand for the indoor ice rink. To reduce energy demand, in this study, an innovative solar shade film was developed and installed between two air cushions in order to reduce solar radiation heat gain. Experimental and numerical studies were carried out to investigate the effect of environmental factors (including seasonal and weather variation) and film materials (transmittance) on the energy-saving potential. Results indicated that high outdoor solar irradiation and air temperature have a significant impact on the energy-saving potential. Meanwhile, the low transmittance of solarshade film reduced solar radiation reaching the room but significantly increased lighting energy consumption. To maximise the energy-saving potential, a transmittance of 0.25 is recommended for the China's National Aquatics Center, with significantly improved predicted total annual energy-saving of 467.3 MJ/m2.

Heating rates are more strongly influenced by near-infrared than visible reflectance in beetles.

Adaptations to control heat transfer through the integument are a key component of temperature regulation in animals. However, there remain significant gaps in our understanding of how different optical and morphological properties of the integument affect heating rates. To address these gaps, we examined the effect of reflectivity in both ultraviolet-visible and near-infrared wavelengths, surface rugosity (roughness), effective area (area subjected to illumination) and cuticle thickness on radiative heat gain in jewel beetles (Buprestidae). We measured heating rate using a solar simulator to mimic natural sunlight, a thermal chamber to control the effects of conduction and convection, and optical filters to isolate different wavelengths. We found that effective area and reflectivity predicted heating rate. The thermal effect of reflectivity was driven by variation in near-infrared rather than ultraviolet-visible reflectivity. By contrast, cuticle thickness and surface rugosity had no detectable effect. Our results provide empirical evidence that near-infrared reflectivity has an important effect on radiative heat gain. Modulating reflectance of near-infrared wavelengths of light may be a more widespread adaptation to control heat gain than previously appreciated.

Experimental comparison of summer thermal performance of green roof (GR), double skin roof (DSR) and cool roof (CR) in lightweight rooms in subtropical climate

Subtropical climate is characterized by high solar altitude angle in summer which causes the roof get more heat through solar radiation. GR, DSR, and CR all can decrease solar radiation heat gain of the roof. However, few researches have been done to the comparison of the thermal performance of these three roofs, especially in subtropical climate. In this study, four rooms were built separately with GR, DSR, CR, and ordinary roof (OR). The experiment was done from July 23 to August 4. Results showed that stabilities of the indoor air temperature of the four rooms were: DSR room &gt; GR room &gt; CR room &gt; OR room. The GR, CR, and DSR can reduce the external surface temperature by 13.7°C, 12.0°C, and 4.8°C during the day while bring a temperature rise of 2.3°C, 1.9°C, and 0.9°C at night. Correlation analysis results showed that the internal surface heat flux of GR and DSR were negative correlated with weather factors while internal surface heat flux of OR and CR were positive correlated with weather factors. This study can give support to the selection between GR, DSR, and CR.

Parametric study of solid-solid translucent phase change materials in building windows

Thermal energy storage and solar radiation management are crucial to improve the sustainability and energy efficiency of buildings. Compared with the implementation of phase change materials (PCMs) in opaque components, the energy saving potential of incorporating PCMs in transparent glazing windows is much less studied and not well understood. Here we present a comprehensive parametric study of novel PCM windows for building energy saving with a focus on optimizing and quantitatively distinguishing the contributions from the optical and thermal properties of the PCM, which is particularly useful for the design of solid-solid PCM windows. We investigate a reference commercial office building using EnergyPlus by developing an equivalent model of our PCM window that is compatible with EnergyPlus’s modeling capabilities. Compared with a clear-clear double-pane window, the integration of 3 mm solid-solid PCMs with optimal properties in warm, mixed, and cold climates can respectively save up to 17.2%, 14.0%, and 5.8% energy for the HVAC (heating, ventilation, and air conditioning) system, and 9.4%, 6.7%, and 3.2% energy for the whole building. We also demonstrate that these energy savings are most sensitive to the solar absorptance of PCMs for all three climates. The optimal transition temperature varies with climate and is related to the climate and solar radiation heat gain. Other issues are also briefly discussed, such as hysteresis, window orientations, and the effect of interior lighting. Although the optimal PCM windows show energy saving performance comparable with low-emissivity windows, the PCM windows provide a unique advantage in terms of shifting HVAC loads which can provide benefits to the electrical grid.

How Can Floor Covering Influence Buildings’ Demand Flexibility?

Although the thermal mass of floors in buildings has been demonstrated to help shift cooling load, there is still a lack of information about how floor covering can influence the floor’s load shifting capability and buildings’ demand flexibility. To fill this gap, we estimated demand flexibility based on the daily peak cooling load reduction for different floor configurations and regions, using EnergyPlus simulations. As a demand response strategy, we used precooling and global temperature adjustment. The result demonstrated an adverse impact of floor covering on the building’s demand flexibility. Specifically, under the same demand response strategy, the daily peak cooling load reductions were up to 20–34% for a concrete floor whereas they were only 17–29% for a carpet-covered concrete floor. This is because floor covering hinders convective coupling between the concrete floor surface and the zone air and reduces radiative heat transfer between the concrete floor surface and the surrounding environment. In hot climates such as Phoenix, floor covering almost negated the concrete floor’s load shifting capability and yielded low demand flexibility as a wood floor, representing low thermal mass. Sensitivity analyses showed that floor covering’s effects can be more profound with a larger carpet-covered area, a greater temperature adjustment depth, or a higher radiant heat gain. With this effect ignored for a given building, its demand flexibility would be overestimated, which could prevent grid operators from obtaining sufficient demand flexibility to maintain a grid. Our findings also imply that for more efficient grid-interactive buildings, a traditional standard for floor design could be modified with increasing renewable penetration.

Influence of permeability ratio on wind-driven ventilation and cooling load of mid-rise buildings

Natural ventilation potential in terraced buildings is affected by numerous parameters such as permeability ratio, distribution pattern, depth of terraces, etc. This research aims to evaluate the impact of permeability ratio on natural ventilation potential and cooling load of a terraced office building in the hot- humid climate. To this end, one solid block and eight porous models with different permeability ratios (20 %–30 %–40 %–50 %) and random distribution patterns were simulated and analyzed by Energyplus engine and computational fluid dynamics (CFD). For better comparison, two distribution patterns for each permeability ratio were simulated. CFD simulations were validated according to the wind-tunnel measurements. The cooling load amount, mean and maximum airspeed as well as the mean age of air in terraces and offices were used to evaluate the best configurations of porous buildings.The results show that increasing the permeability up to 50 % will enhance the interior and inlet airspeed by 38.59 % and 49.07 % compared to the solid case. Simulations proved that a small change in porosities from 20 % to 30 % resulted in a significant difference in mean and maximum airspeed in terraces. The case with 50 % permeability ratio indicated higher values of mean and maximum airspeed in terraces. The mean age of air amount follows a descending process from the permeability ratio of 0–30 % and then increases gradually. The 30 % porous model with 30.8 s mean age of air is considered as the best case.According to the results, the introduction of permeability does not leave a positive effect on cooling energy demand despite natural ventilation performance. Although porosity reduces the solar radiation heat gain and increases the natural ventilation potential, porous models indicated high values of cooling energy consumption. This is due to the high amount of exposed surface area in porous models which leads to an increase of cooling energy demand up to 2.7 % compared to the solid case.As a result, among the permeable models, the best natural ventilation performance and the lowest cooling energy consumption are attributed to 50 % and 20 % permeable groups respectively.This study helps the designers to better understand the ventilation and energy performance of a porous model and to improve the energy-efficient buildings in hot-humid regions.