LEED v5 Daylight Compliance Assessment Report

Case study : Hochiminh office building

Executive Summary

This report presents the daylight assessment and glazing selection for the proposed an Office Tower in Hochiminh city in accordance with the LEED v5 Daylight credit. Following a comparative evaluation of multiple glazing configurations, a double Low-E insulating glazing unit (VLT 46%, U-value 1.65 W/m²K, SHGC 0.24) was selected as the preferred façade solution, providing the best balance between daylight availability and visual comfort. The selected configuration achieved an average sDA of 92% and ASE of 20%, enabling the project to achieve the maximum 4 points under the LEED v5 Daylight credit. High-performance internal roller blinds are recommended as an optional enhancement to further improve glare control and support the achievement of the additional LEED daylight performance point.

1. Project Configuration

Overall Building

Location: Ho Chi Minh City, Vietnam
Building type: Office tower
Building height: 12 above-ground storeys and 4 basement levels
Gross floor area (GFA): 7,182 m²
Typical floor area: Approximately 658 m²

Façade Configuration

Façade system: Unitized curtain wall, Typical panel size: 3.4 m × 1.4 m, Window-to-Wall Ratio (WWR): 73%
Glazing type: Double Low-E insulating glass unit (IGU), Visible Light Transmittance (VLT): 46%, U-value: 1.65 W/m²K, Solar Heat Gain Coefficient (SHGC): 0.24, Aluminium frame reflectance: 20%

Interior Configuration

Interior wall reflectance: 50%, Ceiling reflectance: 70%, Floor reflectance: 20%

Simulation Settings

Simulation software: ClimateStudio (Radiance engine)
Weather file: Ho Chi Minh City EPW
Analysis grid: 0.60 m × 0.60 m
Analysis height: 0.76 m above finished floor level
Assessment methodology: ANSI/IES LM-83 and LEED v5 BD+C Daylight

2. Design Considerations

Ho Chi Minh City has abundant daylight availability throughout the year, with peak global horizontal illuminance exceeding 104,000 lux. Consequently, the primary design challenge is not achieving sufficient daylight, but balancing daylight availability with visual comfort while limiting excessive direct sunlight. Although passive strategies such as external shading and window-to-wall ratio optimisation are generally preferred, the project is currently at the Construction Design stage, where major façade modifications are no longer practical. Therefore, this study focuses on optimising the glazing specification, particularly the visible light transmittance (VLT), to achieve the most balanced daylight performance.

3. Glazing Configuration Selection

To determine the final glazing specification, several glazing configurations with different Visible Light Transmittance (VLT) values were evaluated and compared based on annual daylight performance. Increasing VLT improves Spatial Daylight Autonomy (sDA); however, the improvement becomes marginal beyond 46% VLT, while Annual Sunlight Exposure (ASE), mean illuminance and excessive daylight continue to increase. Considering the overall balance between daylight availability and visual comfort, a glazing configuration with 46% VLT was selected for the final assessment.

VLT(%) sDA(%) ASE(%) Illu(lux) MeanUDI

38% 89.2% 19.7% 1,279 68.5%

46% 94.4% 20.1% 1,540 71.0%

57% 96.9% 20.3% 1,928 71.1%

68% 98.2% 20.9% 2,297 69.2%

74% 98.7% 21.2% 2,480 68.1%

The selected SHGC(g_value) and U-value are based on standard commercially available glazing specifications. Further thermal, energy and façade performance analyses are recommended to validate these parameters before finalising the glazing selection.

4. Final LEED v5 Daylight Assessment

The final glazing configuration fully complies with the LEED v5 Daylight credit requirements. The project achieved an average sDA of 92% and ASE of 20%, earning the maximum 4 points under the LEED v5 Daylight credit. The lower floors exhibit slightly reduced daylight autonomy due to obstruction from surrounding buildings. In contrast, the upper floors achieve almost complete daylight coverage but experience higher direct solar exposure because of reduced external shading.

5. Optional Visual Comfort Enhancement

Although the project complies with the LEED v5 daylight requirements, perimeter areas on the upper floors remain more susceptible to direct sunlight. While external shading devices remain the preferred passive strategy, they are impractical at the current construction stage. As an optional enhancement, high-performance internal roller blinds may be installed to further improve visual comfort and glare control. Suggestion of blind configuration is:

Openness factor: 3%
Visible Light Transmittance (Tv): ≤5%
Visible Light Reflectance (front face): approximately 70%
Colour: Light grey or white
Fire classification: EN 13501-1 or equivalent

References

U.S. Green Building Council. (2025). LEED v5 for Building Design and Construction: Rating System. Washington, DC: USGBC.

Illuminating Engineering Society. (2012). IES LM-83-12: Approved Method – IES Spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE). New York: IES.

Solemma LLC. (2024). ClimateStudio Documentation.

EnergyPlus. (2024). EnergyPlus Weather Data (EPW) Documentation. U.S. Department of Energy.

Software

Rhinoceros 8, Grasshopper, Ladybug Tools, Climate Studio (Radiance)

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