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Thermal mass, a pivotal element in a building's performance, functions as an indoor thermal buffer. While literature underscores its advantages, the enduring impact of thermal mass amid climate change remains uncertain. This study methodically assesses thermal mass effects in 21 Iranian cities across contemporary and future climates, juxtaposing heavyweight and lightweight constructions. The EPSAP algorithm, a generative building design method, created a dataset of two-story single-family houses. Cooling and heating demands were evaluated in EnergyPlus, accounting for current and future system design efficiencies. Future climates were simulated using EC-Earth3 model estimations for the SSP5-8.5 scenario in 2050 and 2080 timeframes. The findings reveal that the energy efficiency advantage of heavyweight over lightweight buildings will diminish by up to 0.60 kW·h·m−2 in 2050 (40 % less than the present-day climate difference between constructions) and 0.93 kW·h·m−2 in 2080 (63 %) for cities in central and southern regions. The performance differences between constructions will sometimes be null, making thermal mass negligible. Conversely, only three cities in Northern Iran exhibit an opposing trend for mid to very-high thermal transmittances. Regarding building geometry, heavyweight construction correlates strongly with indexes related to building compactness, while lightweight construction aligns more with glazing-related indexes. However, as climates warm or we move towards warmer regions, discernible differences between lightweight and heavyweight constructions vanish for both shape- and glazing-related indexes. In conclusion, although the use of thermal mass will be less effective, building design professionals will have greater latitude for innovative construction and design solutions. • Thermal mass will have a lower energy benefit as global warming settles in Iran. • Adequate envelope thermal transmittances enhance thermal mass energy benefits. • Heavyweight construction has a higher correlation with shape-related indexes. • Lightweight construction has a higher correlation with glazing-related indexes. • In the future, no difference is found between constructions' geometry indexes. [ABSTRACT FROM AUTHOR]

Highlights • The U-value impact on the thermal performance of residential buildings was analyzed. • 192000 buildings were randomly generated and evaluated using dynamic simulation. • Six geometry-based indexes were correlated with the buildings performance. • Higher U-values can decrease energy consumption in lower latitudes. • Higher and wider U-value intervals increase the geometric freedom for lower latitudes. Abstract Contrarily to what happens in northern European countries, buildings in the Mediterranean region are prone to overheating. Consequently, it is important to better understand the role that the thermal transmittance of the building envelope elements has on air-conditioning consumptions. This paper analyzes the effect of different U -values on building design in the Mediterranean area. 192 000 residential buildings were randomly generated for sixteen distinct locations and the energy consumption was assessed for each. It was found that in northern Mediterranean locations, as U -values decreased, energy consumption also decreased. However, in warmer climates, low thermal transmittances tended to significantly increase energy consumption. Hence, the lower the latitude, the higher the U -values should be, in order to prevent increasing the cooling demands. Additionally, geometry-based indexes were correlated with the building's energy performance. For high U -values, it was found that bigger buildings worsen the energy performance and larger windows tended to improve it. For low U -values, bigger north-facing windows were beneficial. There is an adequate interval of values for which the geometry has a lower impact, which is wider and higher for lower latitudes, thus meaning that not only does the building performance improve but architects are also freer to explore alternative designs. [ABSTRACT FROM AUTHOR]

Highlights • The U -value impact on the thermal performance of residential buildings was analyzed. • 96,000 buildings were randomly generated and evaluated using dynamic simulation. • Six geometry-based indexes were correlated with the buildings performance. • Low U -values can increase energy consumption in warm and moderate climates. • Adequate U -values allow designers to explore new building forms and window designs. Abstract European countries impose regulations for low thermal transmittance envelopes to improve the buildings' energy efficiency. However, in scientific literature, evidences are surfacing that such low U -values are affecting the validity of traditional design guidelines. The purpose of this paper is to analyze the implications of lowering the envelope U -values. To achieve this, 96,000 residential buildings were generated, with random geometries and U -values, and their energy consumption evaluated for eight European locations. The buildings were grouped according to the envelope elements' thermal transmittance and the results statistically analyzed. For each group, six geometry-based indexes were correlated with the energy performance. As U -values decrease, the performance variation amplitude was found to reduce, making the geometry less important. However, in warm/moderate climates, low U -values tend to actually increase the energy consumption and also rise the performance variation, meaning that geometry regains importance. In this case, instead of helping reducing the heating demands, solar exposed windows and compact geometries raise the energy consumption. It is concluded that, for each climate location, there is an ideal U -value range for which the energy demand is low and the geometry effect becomes less significant, thus freeing designers to further explore building forms and window designs. [ABSTRACT FROM AUTHOR]

This paper presents a study on the application of lightweight steel framed (LSF) construction systems in hot climate. A generative design method created 6010 houses, with random geometry and random roof and exterior wall types with different insulation levels, and EnergyPlus was used to evaluate the energy consumption for air-conditioning of each building. The main goals were to determine which geometric variables correlate with the energy performance, and to provide some guidelines to foster efficient LSF buildings in hot climates. By correlating six geometry-based indexes with the energy consumption for each construction element type group, it was verified that roofs do not show significant correlation, while exterior walls presented weak to moderate positive correlation with the building volume, very weak to weak negative correlation with the relative compactness, no correlation with the shape coefficient, moderate to strong negative correlation with the window-to-floor, window-to-wall, and window-to-exterior surface ratios. The results also show that buildings with larger windows and greater level of insulation have better energy performance. No significant difference of energy performance was found between different LSF construction systems with equivalent thermal resistance. [ABSTRACT FROM AUTHOR]

• Ideal U -values for 2050 climate projection in the Mediterranean region are determined. • Current well insulated buildings are not prone to overheating in the future. • In the future, ideal U -values are similar or even lower than current ones. • Casablanca is the only location presenting an overheating risk. • The increase of cooling demand will overcome the heating demand decrease. One of the effects of climate change is global warming, which will increase cooling demand in buildings. However, scientific literature does not show consensus on the risk of highly insulated buildings being prone to overheating. This paper presents a statistical comparison of two synthetic datasets for current and future climates in sixteen Mediterranean locations. The weather data for the 2050 climate projection was generated by 'morphing' current weather data. The buildings were created using a generative design method to produce random geometries and random U -values for the envelope elements. Energy performance was evaluated using dynamic simulation. In addition to the expected general increase in cooling demand (up to 137 %) and a smaller reduction in heating demand (up to 63 %), the results demonstrate that the ideal U -values used in the current climate in almost all of the locations will not cause overheating. In several cases, the decrease of the U -values is even recommended for Podgorica, Valencia, Tunis, Malaga, Larnaca, and Alexandria, as the reduction of heating demand compensates the increase of cooling demand. Casablanca was the only location showing an increase in the ideal U -values, thus presenting risk of overheating if using current ideal U -values. [ABSTRACT FROM AUTHOR]

Efficient ventilation is an effective method for reducing thermal loads inside buildings, thus decreasing cooling energy consumption. This is especially relevant in warmer climates. Therefore, it is important to better understand the role that different ventilation parameters play on air-conditioning consumptions. This study analyzes the effect of three different ventilation parameters – air flow rate, minimum indoor temperature and indoor-outdoor temperature difference – on the energy performance of buildings in the Mediterranean region. A set of 500 residential building geometries was randomly generated and the energy consumption for different combinations of ventilation parameters was assessed in sixteen distinct locations. Results suggested that the ventilation specifications that minimize air-conditioning energy consumption fall within similar values for all the evaluated locations: ventilation rates of at least 10 air changes per hour, a minimum indoor temperature for ventilation slightly below the building's cooling setpoint, and a low indoor-to-outdoor temperature difference. It was also found that, in lower latitudes, the buildings' energy performance tended to become similar, thus reducing the impact of their geometry and orientation. These results may help building practitioners to infer the most adequate ventilation strategies to implement, since this study is not limited to specific ventilation methods. • The ventilation impact on energy performance of residential buildings was analyzed. • 500 buildings were randomly generated and evaluated using dynamic simulation. • Similar ventilation specifications can be used for all the evaluated locations. • Ventilation rates of at least 10 ACH show to be the most adequate. • In lower latitudes, geometry and orientation are less impacting on energy performance. [ABSTRACT FROM AUTHOR]

• Datasets of low and high thermal mass with random U -values are compared. • Low thermal mass buildings have lower and wider range of ideal U -values. • High thermal mass buildings demand more cooling energy. • Buildings with high thermal mass consume lesser heating energy in warmer climates. • Thermal mass impacts differently the energy consumption along the U -value scale. High thermal mass construction is commonly used to reduce cooling energy consumption during the summer period as a passive design strategy in the Mediterranean region. Although being a generalized design practice, the benefit to the building performance is not fully consensual within the scientific community. This work explores the influence of thermal transmittance on the energy efficiency of buildings with different thermal mass levels. Hence, a statistical comparison of the buildings' annual energy consumption for air-conditioning is carried out based on two synthetic datasets with high and low thermal mass and varying thermal transmittance for opaque and transparent elements. In addition to climate location, the results demonstrate that thermal transmittance has varying impact on the contribution of thermal mass. The locations presenting such behavior were Marseille (−0.99% to +3.89%), Istanbul (−0.73% to +4.21%), Valencia (−1.31% to +4.97%), Algiers (−2.32% to +3.81%), Malaga (−3.95% to +6.21%), Casablanca (−5.66% to +6.96%), and Tel Aviv (−1.81% to +5.44%). These findings demonstrate that the influence of thermal mass is more complex than previously thought and levels should be chosen in relation with the thermal transmittance value. [ABSTRACT FROM AUTHOR]

The climate will become hotter, and buildings will perform differently as outdoor conditions evolve. If the lowest energy demand is desired, it is crucial to determine the ideal thermophysical properties of the envelope over the buildings' life span. However, the scientific literature is still scarce in providing a compelling answer. Therefore, this study (i) determines ideal thermal transmittance values (U -values) for present-day and future climates, (ii) determines to what extent the thermophysical properties will need to change to remain ideal, (iii) identifies different trends of U -values over time, (iv) establishes a relationship between outdoor air temperatures, cooling and heating setpoints, and ideal U -values, and (v) proposes a set of design strategies according to each trend. The EPSAP generative design method was used to create a large dataset of residential buildings with random geometries and U -values to evaluate their energy demand for heating and cooling in EnergyPlus. The thermal performance of each building was evaluated for 30 locations in Brazil for the current period and two future timeframes (2050 and 2080). The Future Weather Generator tool was used to morph today's typical meteorological weather to match the EC-Earth3 data for the SSP5–8.5 scenario. Although climate change has a similar relative impact, its consequences differ over time in each location. The ideal U -values have different trends in different regions: (a) remaining unchanged in the future, (b) changing from being the highest possible to the lowest of the analyzed range in 2050 or 2080, and (c) being mid-range values in the present and with similar or lower values in the future climate. The impact on the thermal loads of maintaining the present-day ideal U -values also varies significantly in the future timeframes, from being nil to representing an increase reaching 30 % in 2050 (∆ 2.94 MW·h ± 0.06 MW·h) and 57 % in 2080 (∆ 6.05 MW·h ± 0.09 MW·h). Therefore, building design professionals need to use different strategies according to each region and consider how climate evolves during the lifetime of the building. • Ideal U -values in present-day and future climates in Brazil are determined. • The trend of the ideal U -values varies according to each region. • A relation between U -values and outdoor temperatures and HVAC setpoints was found. • A fast procedure is presented to determine the trend of the ideal U -values over time. • For each trend, building design strategies are proposed. [ABSTRACT FROM AUTHOR]