IS 5281 (Israeli Standard)
In Israel, pedestrian wind comfort and safety analyses are mandated for new — and in certain cases, existing — developments. The IS 5281 guidelines assess outdoor wind conditions for both comfort and safety. The 6 m/s and 9 m/s thresholds are explicitly defined as uncomfortable wind speeds; exceedance beyond the limits below is not suitable and requires mitigation.
IS 5281 Comfort Categories (V_eq)
| Wind Comfort Category | Exceedance Frequency (V_eq > 6 m/s) | Exceedance Frequency (V_eq > 9 m/s) | Typical Areas | Color |
|---|---|---|---|---|
| Sitting / Prolonged Stay | ≤ 20% | ≤ 5% | Outdoor seating, cafés, playgrounds, public seating, waiting areas | |
| Walking / Brief Stay | ≤ 25% | ≤ 10% | Pedestrian areas, entrances, access paths | |
| Short-duration Activity | ≤ 35% | ≤ 15% | Streets, plazas, sidewalks, balconies, short stops | |
| Not Suitable (Exceeds Comfort Limits) | > 35% | > 15% | Not suitable for any activity; mitigation required |
IS 5281 Safety Criteria (V_eq)
| Wind Safety Rating | Threshold (V_eq) | Max Exceedance | Applies To | Color |
|---|---|---|---|---|
| Pass | 20 m/s | ≤ 0.1% (~8 hours/year) | Sitting / prolonged-stay areas | |
| Limited Risk | 20 m/s | > 0.1% and ≤ 0.2% (~16 hours/year) | Walking / short-duration areas only | |
| Exceeded (Hazardous) | 20 m/s | > 0.2% | Unacceptable for all scenarios |
Wind Speed Metric (V_eq)
IS 5281 uses Equivalent wind speed (V_eq), which incorporates turbulence using a fixed coefficient α = 3:
$$ V_{eq} = V_{mean}(1 + \alpha I) $$
where:
V_mean= mean horizontal wind speedI= turbulence intensityα= 3 (mandatory for Israeli studies)
Meteorological Data Source
All IS 5281 studies must use the Israel Meteorological Service Wind Energy Potential Atlas, processed via the recommended WEIBULLEXTRA tool, for long‑term wind statistics. Alternative local datasets are only acceptable if they meet the guideline’s strict equivalence requirements.
This source is selectable on the simulation launch page under Wind data source.
