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IS 3362:1977 is the Indian Standard (BIS) for natural ventilation of public buildings. This standard provides design guidelines for natural ventilation in public buildings. It outlines methodologies for calculating airflow based on wind action and stack effect, and provides recommended air change rates for various types of public occupancies to maintain indoor air quality and comfort.
Provides recommendations for achieving adequate natural ventilation in various types of public buildings.
CIBSE Guide A: 2015CIBSE (Chartered Institution of Building Services Engineers), UK
HighCurrent
Guide A: Environmental Design
Provides comprehensive design guidance for natural ventilation in non-domestic buildings, covering principles, calculations, and system design.
ASHRAE Standard 62.1-2022ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers), USA
MediumCurrent
Ventilation and Acceptable Indoor Air Quality
Offers a prescriptive and performance-based path for natural ventilation to meet minimum outdoor air requirements in commercial and institutional buildings.
EN 16798-7:2017CEN (European Committee for Standardization), Europe
MediumCurrent
Energy performance of buildings - Ventilation for buildings - Part 7: Calculation methods for the determination of air flow rates in buildings including infiltration (Module M5-5)
Focuses on the detailed calculation methods for airflow rates, which are essential for designing and verifying natural ventilation systems.
BS 5925:1991BSI (British Standards Institution), UK
HighWithdrawn
Code of practice for ventilation principles and designing for natural ventilation
Provided a prescriptive code of practice similar in philosophy and approach to IS 3362, focusing on fundamental principles and design rules of thumb.
Key Differences
≠IS 3362 is a prescriptive code based on empirical formulas and recommended air change rates, whereas modern standards like ASHRAE 62.1 and CIBSE Guide A heavily incorporate performance-based design using dynamic thermal simulation and airflow network models.
≠International standards explicitly address hybrid or mixed-mode ventilation (integrating natural and mechanical systems) and automated controls (e.g., window actuators linked to CO2/temperature sensors), topics not covered in the 1977 Indian standard.
≠Modern standards like ASHRAE 62.1 and EN 16798 place a strong emphasis on maintaining indoor air quality (IAQ) by setting limits for specific pollutants like CO2, whereas IS 3362's primary metric is volumetric airflow (air changes per hour).
≠IS 3362 relies on simplified assumptions for environmental factors (e.g., assuming a fraction of mean wind speed), while CIBSE and ASHRAE mandate the use of detailed, location-specific hourly weather data files for analysis.
Key Similarities
≈All standards are founded on the same two fundamental physical principles for driving natural airflow: the pressure differences created by wind (cross-ventilation) and temperature differences creating a buoyancy or stack effect.
≈Both IS 3362 and its international counterparts emphasize that the effectiveness of natural ventilation is critically dependent on the sizing, placement, and orientation of ventilation openings (inlets and outlets).
≈All codes link the required ventilation rate to the building's use and occupancy density, recommending higher airflow rates for spaces with more people or higher activity levels, such as auditoria and classrooms versus offices.
≈They all provide qualitative architectural guidance, such as orienting the building to prevailing winds and strategically locating openings to promote effective air distribution throughout the occupied zones.
Parameter Comparison
Parameter
IS Value
International
Source
Primary Ventilation Metric
Air Changes per Hour (ACH)
Litres per second per person (L/s/p) and/or Litres per second per square meter (L/s/m²), often with target indoor CO₂ concentration.
ASHRAE 62.1 / CIBSE Guide A
Minimum Ventilation Rate (Office)
6 ACH
Typically 8-10 L/s per person. ASHRAE 62.1 specifies 2.5 L/s/p + 3 L/s/m².
CIBSE Guide A / ASHRAE 62.1-2022
Minimum Ventilation Rate (Classroom)
8 ACH
Typically 8-10 L/s per person, with ASHRAE 62.1 specifying 5 L/s/p + 3 L/s/m².
CIBSE Guide A / ASHRAE 62.1-2022
Prescriptive Opening Area (General)
Recommends area based on achieving required ACH; often interpreted as 5-10% of floor area.
Requires total openable area to be at least 4% of the net occupiable floor area.
ASHRAE 62.1-2022
Wind Speed Assumption for Design
Recommends using 1/3rd to 1/2 of the mean wind speed for the locality.
Requires use of hourly meteorological weather data (e.g., TMY/AMY files) for simulation-based performance analysis.
CIBSE Guide A
Control Requirement for Natural Ventilation
Assumes manual operation; no specific control requirements are mentioned.
Requires natural ventilation systems to have manual or automatic controls. ASHRAE 62.1 requires readiness to open and labeling for manual controls.
ASHRAE 62.1-2022
Vertical Separation for Stack Effect Openings
No specific minimum distance prescribed, but effectiveness is noted to increase with height.
Requires low and high openings to have a vertical separation (Δh) of at least 1.5 m (5 ft) for the natural ventilation procedure.
ASHRAE 62.1-2022
⚠ Verify details from original standards before use
Key Values6
Quick Reference Values
Coefficient (K) for wind perpendicular to opening0.6
Coefficient (K) for wind at 45 degrees to opening0.3
Recommended ACH for assembly rooms/auditoriums4 to 6
Recommended ACH for hospital wards6 to 8
Recommended ACH for offices3 to 6
Recommended ACH for libraries3 to 5
Key Formulas
Q = K * A * V — Rate of air flow due to wind action
Q = 7.0 * A * sqrt(h * dt) — Rate of air flow due to stack effect (temperature difference)
Tables & Referenced Sections
Key Tables
Table 1 - Recommended Rates of Air Change for Public Buildings
Key Clauses
Clause 4 - Principles of Natural Ventilation
Clause 5 - Rate of Ventilation
Clause 6 - Ventilation by Wind Action
Clause 7 - Ventilation by Stack Effect
Clause 8 - Guidelines for Design of Natural Ventilation