Influence of Building Orientation and Glazed Terrace Design on Passive Solar Heat Gain in Residential Buildings

1.1. Review of the Related Work

The influence of building form on energy consumption has been extensively investigated, emphasizing the critical role of architectural geometry and design parameters. Korolija et al. [6] highlight that building parameters, including form, coupled with HVAC system integration, significantly impact overall energy performance. Their analysis suggests that optimizing building parameters can lead to substantial energy savings, underscoring the importance of form in energy-efficiency strategies.

Sensitivity analysis conducted by Kistelegdi et al. [8] further confirmed that basic building geometry, such as shape and size, directly affects energy use. Their study demonstrated that variations in geometric configurations can alter energy consumption patterns, indicating that even minor modifications in form can yield notable performance differences. Similarly, Kistelegdi et al. [8] developed predictive algorithms that incorporate building shape and complexity, emphasizing that early-stage design considerations of the form are crucial for energy-saving outcomes. Their approach enables architects to evaluate the impact of form on energy performance during the initial design phase, thereby facilitating more sustainable architectural solutions.

The characteristics of building envelopes, which are inherently linked to their form, also influence energy performance. Shi et al. [9] examined how architectural envelope features affect energy efficiency in Central European climates, finding that envelope design-such as surface area and insulation properties-interacts with form to modulate energy consumption. This aligns with the discussion by Ascione et al. [10] on regional material integration and low-carbon building design, where the architectural form must adapt to material choices to achieve energy-efficiency and sustainability goals.

The urban context and density further modulate the relationship between the building form and energy use. Salvati et al. [11] analyzed the impact of urban density, revealing that the influence of form parameters on energy use intensity varies with city-specific factors. Their findings suggest that the optimal building form for energy performance is context-dependent and influenced by the surrounding urban density and spatial configuration.

Recent studies have explored specific morphological parameters and their optimization for energy efficiency. Ying et al. [12] investigated U-shaped office buildings and identified critical ratios, such as the depth-length ratio (M1) and the modified length (M2), that significantly affect energy consumption. Their contour plots illustrate how morphological parameters can be tuned to minimize energy use, providing practical guidelines for low-energy building designs.

Innovative approaches to form optimization were exemplified by Zou et al. [13], who employed an intelligent performance-based optimization platform to generate and evaluate multiple building prototypes. Their case study on atrium-style office buildings demonstrated that the form can be systematically optimized using data-driven methods to enhance energy performance.

In summary, the reviewed literature consistently underscores that building form-encompassing geometric shape, envelope characteristics, and spatial configuration-plays a pivotal role in determining energy consumption performance. The integration of early-stage design algorithms, sensitivity analyses, and intelligent optimization techniques offers promising pathways for developing energy-efficient architectural forms tailored to specific climatic and urban contexts [6-13].

2.1. Building Envelope and Glazing Properties

The experimental building was constructed using locally available building materials commonly used in residential construction in Uzbekistan. Four external wall configurations with different thermal resistance values were investigated to evaluate their influence on heat loss and passive solar heating performance. The thermal characteristics of the investigated wall systems are summarized in Table 2.

The best-performing wall configuration consisted of a multilayer system including a 320 mm cinder block wall, a 150 mm reed insulation layer, and an external 120 mm brick masonry protective layer. The overall thermal resistance of this wall assembly was 4.30 m²·K/W, providing substantially improved thermal insulation compared with the conventional wall systems.

The experimental building incorporated double-glazed wooden-frame windows. Two windows measuring 1.2 × 1.5 m and one south-facing glazed terrace measuring 7.0 × 2.6 m were installed. The total glazing area was 21.8 m². Since the manufacturer's technical data were unavailable, typical values reported in the literature for conventional double-glazed wooden-frame windows were adopted (Table 3).

The total external wall area of the experimental building was approximately 87.6 m², resulting in an overall Window-to-Wall Ratio (WWR) of approximately 25%. The same WWR, construction materials, and building dimensions were maintained throughout the comparative analyses so that only the effects of building geometry, orientation, and glazed terrace configuration influenced the thermal performance.

To evaluate the influence of building form, orientation, and glazing configuration on energy consumption, theoretical heat-transfer calculations and experimental investigations were conducted using climatic data corresponding to the Tashkent region. All theoretical calculations, data processing, and graphical analyses were performed using Microsoft Excel. The calculations were performed under representative climatic conditions, including average annual outdoor temperatures of 12–14°C, maximum summer temperatures of 38–40°C, and minimum winter temperatures down to −5°C. Solar radiation intensity and wind velocity values were adopted according to ShNQ 2.01.01-22 [14].

Indoor environmental conditions were monitored continuously during the experimental period. Indoor air temperature and relative humidity varied according to outdoor climatic conditions and the operation of the heating system. Relative humidity ranged from approximately 40% to 60%, while occupancy reflected normal residential use. To ensure comparability between different building forms, identical construction materials, thermal properties, window-to-wall ratio (WWR), and total building dimensions were maintained for all investigated models, while only the geometric configuration of the buildings was modified. External shading effects from surrounding buildings and vegetation were neglected.

The analysis was based on the principles of Building Physics, Passive Solar Design, and Heat Transfer Theory. Particular attention was given to the influence of building compactness, façade orientation, glazing configuration, and surface-to-volume ratio (A/V) on heat loss and solar heat gain, as these parameters significantly affect the thermal performance and energy demand of buildings [15-17]. Previous studies demonstrated that compact building forms with lower surface-to-volume ratios exhibit reduced heat losses and improved thermal efficiency [18-20]. Therefore, comparative analysis was performed for several building geometries having identical internal volumes but different compactness ratios and external envelope areas [21, 22].

Theoretical assessment of heat transfer through the building envelope was performed using the standard heat-loss equation (Eq. 1). This equation was used to estimate the heat loss through the external walls under different indoor and outdoor temperature conditions.

where U is the heat transfer coefficient (W/m²·K), A is the external envelope area (m²), and T_in and T_out are the indoor and outdoor air temperatures, respectively.

Solar heat gain through glazed surfaces was calculated using Eq. (2). This equation was applied to evaluate the influence of façade orientation and glazing configuration on passive solar heat gain.

where I - is solar radiation intensity (W/m²),

SHGC - is the solar heat gain coefficient, and θ is the solar incidence angle.

The influence of façade orientation and glazing area on solar heat gain and indoor thermal stability was evaluated using the approaches described in previous studies [23-26].

Experimental investigations were conducted on an energy-efficient, low-rise residential house constructed from local materials in the Tashkent region (Fig. 1). The investigated external wall configurations with varying thermal resistances are illustrated in Fig. (2).

The external wall consisted of a multilayer structure including concrete blocks, a 150 mm reed insulation layer, and an external brick masonry layer. The overall thermal resistance of the wall assembly was R ₀ = 4.3 (m².°C)/W. The external wall consisted of a multilayer structure including concrete blocks, a 150 mm reed insulation layer, and an external brick masonry layer. The overall thermal resistance of the wall assembly was 4.30 m²·K/W. The physical and thermal properties of the principal building materials used in the investigated wall and envelope systems are summarized in Table 4.

2.2. Experimental Measurements

Experimental measurements were carried out to evaluate the influence of building orientation and the south-facing glazed terrace on indoor thermal conditions and passive solar heat gain. Indoor air temperature, relative humidity, and surface temperatures of the building envelope were monitored during the heating season under real climatic conditions.

Indoor air temperature and relative humidity were measured using an Assmann aspirated psychrometer (Fig. 3). The instrument was installed at the center of the experimental room at a height of 1.2–1.5 m above the floor, representing the occupied zone according to standard indoor environmental measurement practice. To avoid local thermal disturbances, the psychrometer was positioned at least 1.0 m away from windows, heating appliances, ventilation openings, and exterior walls.

Measurements were performed three times daily at 08:00–09:00, 13:00–14:00, and 18:00–19:00. Each measurement was repeated three times, and the arithmetic mean value was used for subsequent analysis.

Continuous monitoring of indoor air temperature and relative humidity was conducted using a DT-172 temperature and humidity data logger (Fig. 3). The data logger was installed adjacent to the Assmann psychrometer at a height of 1.2–1.5 m above the floor and protected from direct solar radiation. The recording interval was set to 10 minutes, enabling continuous monitoring throughout the experimental period. The DT-172 has a measurement range of −40 to +70°C for temperature and 0–100% RH for relative humidity, with accuracies of ±1.0°C and ±3.5% RH, respectively.

Surface temperatures of the external walls, glazed terrace, window glazing, floor, ceiling, and window frames were measured using a digital non-contact infrared thermometer (Fig. 3). Measurements were performed with the instrument positioned perpendicular to the measured surface at the manufacturer's recommended distance. Each measurement point was recorded three times, and the average value was used in the analysis. Measurements were carried out during periods with minimal direct solar radiation to reduce reflection errors.

Rapid surface temperature variations were monitored using a digital low-inertia thermometer equipped with K-type thermocouples (Fig. 3). Thermocouples were attached directly to selected locations on the external walls, glazed terrace, window glazing, floor, and ceiling using thermal contact tape to ensure good thermal contact and minimize measurement uncertainty. These sensors enabled continuous observation of transient thermal responses caused by solar radiation and outdoor climatic variations.

In addition, a weekly M-16AN thermograph was employed to obtain continuous records of indoor air temperature during selected monitoring periods (Fig. 3). The combined use of manual measurements, automatic data logging, infrared surface temperature measurements, and thermocouple monitoring improved the reliability of the experimental data and enabled comprehensive evaluation of the building's thermal performance.

The experimental campaign has been conducted over eight consecutive heating seasons (2017–2025), providing a comprehensive database for evaluating the long-term influence of passive solar heating and building orientation on indoor thermal conditions and heating energy demand under the climatic conditions of the Tashkent region.

The experimental building incorporated a south-facing glazed terrace that served as a passive solar heating element. Indoor temperature and humidity measurements were performed using an Assmann aspirated psychrometer, DT-172 temperature and humidity data logger, digital thermometers, and thermocouples with a measurement accuracy of ±0.1°C (Fig. 3). Continuous monitoring was conducted during the coldest and hottest periods of the year to evaluate the thermal performance of the investigated building systems.