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Beräkna IREQ och WCT

On this page you can calculate the following:

  • Required clothing insulation (IREQ) and Duration limited exposure (Dlim)
  • Required recovery time (RT)
  • Wind chill temperature (twc) 

For interpretation of the results, read the standard, ISO 11079.

Required clothing insulation (IREQ) and Duration limited exposure (Dlim)

M (W/m2), Metabolic energy production (58 to 400 W/m2)
W (W/m2), Rate of mechanical work, (normally 0)
Ta (C), Ambient air temperature (< +10 C)
Tr (C), Mean radiant temperature (often close to ambient air temperature)
p (l/m2s), Air permeability (low < 5, medium 50, high > 100 l/m2s)
w (m/s), Walking speed (or calculated work created air movements)
v (m/s), Relative air velocity (0.4 to 18 m/s)
rh (%), Relative humidity
Icl (clo), AVAILABLE basic clothing insulation (1 clo = 0.155 W/m2K)

IREQ & Dlim results (minimal to neutral)

Insulation Required, IREQ to (clo)

Required basic clothing insulation (ISO 9920), Icl to (clo)

Duration limited exposure, Dlim to (hours)

Calculation of Required Recovery Time, RT

M (W/m2), Metabolic energy production, (normally lower!)
W (W/m2), Rate of mechanical work, (normally 0)
Ta (C), Ambient air temperature, (normally warmer!)
Tr (C), Mean radiant temperature, (normally warmer!)
p (l/m2s), Air permeability
w (m/s), Walking speed (normally lower)
v (m/s), Relative air velocity (normally lower!)
rh (%), Relative humidity
Icl (clo), Available basic clothing insulation, (normally lower!)

RT Results (neutral)

Required recovery time (hours)

Calculation of Winchill Temperature, twc

v (km/h), Meteorological wind speed (at 10 m)
Ta (C), Ambient air temperature


Wind chill temperature, twc (C)


ISO 11079, 2007-12-15, Ergonomics of the thermal environment - Determination and interpretation of cold stress when using required clothing insulation (IREQ) and local cooling effects. 

Contact: Chuansi Gao, chuansi.gao@design.lth.se 


The authors disclaim all obligations and liabilities for damages arising from the use or attempted use of the information, including, but not limited to, direct, indirect, special and consequential damages, and attorneys' and experts' fees and court costs.
Any use of the information will be at the risk of the user.

Sidansvarig: info@design.lth.se | 2022-05-30