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IS 12818:1990 is the Indian Standard (BIS) for guidelines for design of solar passive buildings. This standard provides guidelines for designing energy-efficient buildings by utilizing passive solar techniques. It covers key principles such as building orientation, form, envelope design, shading, and natural ventilation for thermal comfort. The code aims to reduce reliance on active heating and cooling systems by optimizing the building's interaction with the local climate.
Provides principles and guidelines for designing buildings that harness natural solar energy for heating, cooling, and lighting, reducing conventional energy demand.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! This code is a foundational guideline; for detailed energy performance calculations and compliance, refer to the Energy Conservation Building Code (ECBC).
! The principles are highly climate-zone dependent. Strategies must be adapted for hot-dry, warm-humid, or composite climates as defined in SP 41 or the NBC.
! Effective passive design requires an integrated approach, considering architectural form, material selection, and site planning from the initial concept stage.
ISO 17772-1:2017ISO (International Organization for Standardization)
HighCurrent
Energy performance of buildings — Indoor environmental quality — Part 1: Indoor environmental input parameters for design and assessment of energy performance of buildings
Matches on defining the indoor environmental criteria (thermal, visual, acoustic) that passive design aims to satisfy.
ASHRAE 55-2020ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers), USA
HighCurrent
Thermal Environmental Conditions for Human Occupancy
Matches on the core goal of defining and achieving human thermal comfort, a primary driver for passive solar design.
CIBSE Guide A: 2015CIBSE (Chartered Institution of Building Services Engineers), UK
HighCurrent
Environmental Design
Matches by providing comprehensive design guidance on achieving thermal comfort and good daylighting through passive means.
EN 16798-1:2019CEN (European Committee for Standardization), Europe
HighCurrent
Energy performance of buildings - Ventilation for buildings - Part 1: Indoor environmental input parameters for design and assessment of energy performance of buildings addressing indoor air quality, thermal environment, lighting and acoustics
European equivalent of ISO 17772-1, focusing on the target environmental parameters for building design.
Key Differences
≠IS 12818 is primarily a prescriptive guideline with rule-of-thumb recommendations, whereas modern international standards like ASHRAE 55 and ISO 17772 are more performance-based, setting criteria and allowing various methods to achieve them.
≠IS 12818 is specific to Indian climatic zones and provides data for Indian cities. International standards are globally applicable, providing methodologies that require local climate data as an input.
≠Modern standards like ASHRAE 55 incorporate the Adaptive Comfort Model, which relates acceptable indoor temperatures to outdoor conditions, highly relevant for naturally ventilated passive buildings. IS 12818 uses a simpler, static comfort temperature range.
≠IS 12818 focuses almost exclusively on passive measures. In contrast, modern frameworks like those from ASHRAE and CIBSE are designed to holistically integrate passive design with active (mechanical) systems for overall building performance.
Key Similarities
≈All standards are founded on the same core principles of passive solar design: optimizing orientation, controlling solar gain with shading, utilizing thermal mass, promoting natural ventilation, and maximizing useful daylight.
≈The fundamental goal across all standards is to achieve a comfortable and healthy indoor environment for occupants while minimizing reliance on non-renewable energy.
≈Both IS 12818 and its international counterparts emphasize the critical importance of fenestration design, including size, placement, orientation, glazing properties, and shading, as a key driver of building performance.
≈All documents recognize site planning and building orientation as the most crucial first steps in effective passive design, influencing the building's energy balance throughout its life.
Parameter Comparison
Parameter
IS Value
International
Source
Thermal Comfort Temperature (Warm-Humid Climate)
25°C to 30°C with significant air movement.
Adaptive model allows an operative temperature range of ~25-31°C for a mean monthly outdoor temperature of 30°C.
ASHRAE 55-2020
Natural Ventilation Opening Area (Rule of Thumb)
Minimum 10% (1/10th) of the floor area.
Suggests a minimum operable area of 5% of the gross floor area as a baseline for simple natural ventilation strategies.
CIBSE Guide A: 2015
Average Daylight Factor for Offices
2% for general office spaces.
2% for general offices (where tasks are predominantly screen-based).
CIBSE Guide A: 2015
Shading for South Facade (Summer)
Recommends horizontal overhangs with a Projection Factor (Projection/Window Height) of ~0.4-0.5 for 28°N latitude.
Provides detailed graphical (sun-path diagrams) and calculation methods to design shading to block high-angle summer sun while admitting low-angle winter sun.
CIBSE Guide A: 2015
Window Wall Ratio (WWR) Guideline
Recommends limiting glass area on east and west facades, without a strict maximum WWR.
Prescribes maximum WWR of 40% (for the whole building) and provides trade-off options if exceeded, with specific limits for different climate zones.
ASHRAE 90.1-2019 (Related Energy Standard)
Indoor Air Velocity for Comfort in Warm Climates
Recommends air speed of 0.8 to 1.4 m/s for comfort at 30°C.
Specifies that elevated air speed (up to 1.2 m/s) can be used to offset an increase in temperature, with specific criteria for occupant control.
ASHRAE 55-2020
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Recommended Building OrientationLong axis oriented East-West
Recommended Window Opening for Cross-Ventilation15% to 20% of floor area
Thermal Mass Wall Thickness for Hot-Dry Climate200 mm to 300 mm
Roof Insulation U-Value for Hot-Dry Climate< 0.4 W/m²K
Recommended Reflectivity for External Walls (Hot Climate)> 0.70
What is the ideal building orientation according to this code?+
The long axis should be oriented East-West to minimize heat gain on the larger wall surfaces and maximize controllable southern exposure (Clause 4.3).
What are the main passive heating concepts mentioned?+
Direct Gain (sunlight through windows), Indirect Gain (using a thermal mass like a Trombe wall), and Isolated Gain (collecting heat in a separate space like a sunroom) (Clause 6).
What is a Trombe wall?+
It's an indirect gain passive heating system comprising a dark-colored masonry wall with an air gap and exterior glazing to trap and slowly release solar heat (Clause 6.3).
How can passive cooling be achieved in buildings?+
Through strategies like shading of windows and walls, promoting natural ventilation (cross-ventilation and stack effect), and using evaporative cooling (Clause 7).