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.
In Jerusalem, the municipality applies a closely related framework derived from IS 5281 with local adaptations. The core methodology (V_eq definition, turbulence coefficient, exceedance-based evaluation) is the same, but Jerusalem introduces additional thresholds and stricter safety limits.
IS 5281 Comfort Categories (V_eq)
| Category | Exceedance frequency (V_eq > 6 m/s) | Exceedance frequency (V_eq > 9 m/s) | Typical areas |
|---|---|---|---|
| Sitting / Prolonged Stay | ≤ 20% | ≤ 5% | Outdoor seating, cafes, 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 |
Jerusalem Comfort Categories (V_eq)
The Jerusalem municipal guideline uses the same V_eq formulation with stricter comfort limits for the 6 m/s and 9 m/s thresholds.
| Category | Exceedance frequency (V_eq > 6 m/s) | Exceedance frequency (V_eq > 9 m/s) | Typical areas |
|---|---|---|---|
| Sitting | ≤ 10% | ≤ 5% | Open restaurants, city squares, open public spaces, courtyards of public institutions |
| Walking | ≤ 15% | ≤ 10% | Business and commercial areas, residential areas, entrances to buildings, passages defined as easement areas, passages between buildings |
| Very short stay | ≤ 20% | ≤ 10% | Sidewalks and parking lots |
| Not Suitable (Exceeds Comfort Limits) | > 20% | > 10% | Not suitable for any activity; mitigation required |
These limits apply at pedestrian height and at all occupied outdoor levels.
IS 5281 Safety Criteria (V_eq)
| Category | Exceedance frequency (V_eq > 20 m/s) | Typical areas |
|---|---|---|
| Sitting / Prolonged Stay | ≤ 0.1% (~9 hours/year) | Outdoor seating, cafes, playgrounds, public seating, waiting areas |
| Walking / Brief Stay | ≤ 0.2% (~18 hours/year) | Pedestrian areas, entrances, access paths |
| Short-duration Activity | ≤ 0.2% (~18 hours/year) | Streets, plazas, sidewalks, balconies, short stops |
| Hazardous (Exceeds Safety Limits) | > 0.2% | Unacceptable for all scenarios |
Jerusalem Safety Criteria (V_eq)
Jerusalem applies stricter safety requirements than IS 5281.
| Category | Exceedance frequency (V_eq > 15 m/s) | Exceedance frequency (V_eq > 20 m/s) | Typical areas |
|---|---|---|---|
| Pass | ≤ 1.50% (~130 hours/year) | ≤ 0.01% (~1 hour/year) | All regions |
| Hazardous (Exceeds Safety Limits) | > 1.50% | > 0.01% | 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)
This same formulation is used in the Jerusalem municipal guideline.
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.
Jerusalem municipal studies typically use local meteorological station data with correction factors, as required by the municipality.
This source is selectable on the simulation launch page under Wind data source.
IS 5281 Specific Methodology In ArchiWind
For IS 5281 studies in ArchiWind:
- 12 wind directions are simulated
- wind statistics are consumed in their native 12-direction form
.TABclimate files are supported directly- the simulation domain is set to 600 m to improve wind development and surrounding context