Handbook on Functional Requirements of Buildings (Other than Industrial Buildings)
1987 Edition

For spaces under 30 m² targeting a daylight factor of around 2.5% at the furthest point, the recommended window area as a percentage of floor area is about 22.5% for windows placed on the shorter wall with metallic frames, and approximately 16.1% when located on the longer wall. Adjustments include multiplying by 1.15 for floor areas below 30 m² and by 0.85 for areas exceeding 50 m². External obstructions necessitate increasing window size depending on the obstruction height to distance ratio. The window area can be calculated by: Window Area = (Fenestration % × Floor Area)/100. For rooms deeper than 10 m, windows on opposite sides are advised to ensure bilateral daylighting. Using light-colored interior finishes like white or off-white can enhance daylight penetration by around 7%.

The standard emphasizes passive design strategies for non-air-conditioned buildings, focusing on optimizing building orientation, shading, window placement, insulation, and choice of materials to reduce solar heat gain and moderate surface temperatures. It sets thermal performance limits for building elements based on climatic zones. Adequate natural ventilation is critical, specifying minimum wind speeds necessary for occupant comfort or acceptable warm conditions depending on temperature and relative humidity. When passive means are insufficient, mechanical cooling may be necessary. This balanced approach aims to maintain occupant comfort through design rather than solely relying on air-conditioning.

The code distinguishes between three ventilation categories: Health Ventilation, which maintains air quality by ensuring appropriate CO₂ and oxygen levels and is mandatory across climates; Comfort Ventilation, which enhances thermal comfort by promoting heat loss when indoor temperatures exceed outdoors; and Systems of Ventilation including Natural (utilizing windows, louvers, and wind), Mechanical (fan and duct systems), or a combination of both, depending on building function. Residential and public buildings typically use natural or mechanical systems to provide health and comfort ventilation, while kitchens require enhanced ventilation to remove combustion products. Louvers of various designs facilitate natural airflow while preventing rain ingress.

For artificial lighting, the standard advocates the Lumen Method for general illumination, calculating total required lumens based on room dimensions and surface reflectance, and the Point-by-Point Method for localized task lighting, considering fixture placement and light distribution. Offices benefit from semi-direct luminaires to efficiently illuminate work areas and surroundings, with supplementary lighting designed per power density guidelines during low daylight. Residential spaces typically use bare fluorescent tubes or incandescent lamps equipped with white enameled conical reflectors inclined at approximately 45° to optimize light spread. Combining daylighting design with supplementary artificial lighting enhances energy efficiency and visual comfort.

The Thermal Performance Index (TPI) quantifies the thermal efficiency of building elements and is calculated differently for non-air-conditioned and air-conditioned components. For non-AC elements: TPI = ((T_is - 30) × 100) / 8, where T_is is the peak inside surface temperature in °C; for AC elements: TPI = (q_is - 46) × 2.5, where q_is is the peak heat gain factor in W/m². The TPI is expressed as a percentage, with higher values indicating poorer thermal performance, categorized from A (best) to E (worst). It aids in comparing materials and designs suited for specific climates. Peak surface temperature and heat gain can also be derived from TPI using provided formulas, with correction factors available for real-world conditions.