# UTCI explained
The UTCI tab allows users to analyze outdoor thermal comfort for a combination of different meteorological conditions based on the presence or absence of sun and wind.
Clima leverages the several models implemented in [Pythermalcomfort](https://pythermalcomfort.readthedocs.io/en/latest/).
* The "[Solar gain on people](https://pythermalcomfort.readthedocs.io/en/latest/reference/pythermalcomfort.html#solar-gain-on-people)" calculates the solar gain to the human body, so the mean radiant temperature. To simulate a sunless situation, Clima considers the person surrounded by surfaces that shade him, all of which tend toward dry bulb temperature;
* Wind data is obtained directly from the weather file. The windless situation sets the value at 0.5 m/s, which is the minimum value allowed by the UTCI model.
The UTCI can then be visualized for the entire year for the scenario chosen.
UTCI perceived temperature annual heatmap in the four conditions for Rome, ITA
The values are then converted into a scale assessing thermal stress, either because of cold or heat. Therefore, a second chart maps if people will experience thermal stress for all the hours of the year for corresponding UTCI temperatures.
UTCI heat stress index heatmap in the four conditions for Rome, ITA
The UTCI is a useful tool to design the outdoor space, to maximize the number of comfortable hours. The designer can influence two factors out of the four driving outdoor comfort: radiant temperature (i.e. exposure to the sun) and wind speed (i.e. exposure to the wind).
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