Poorly tempered trams

In winter you freeze in the trams, in summer you sweat. Supposedly because the VBZ want to save energy. I just don't understand how you can save energy when the fan is fully switched on in order to cool down the trams when the outside temperatures are cold. Actually, the VBZ should put the well-being of the passengers in the foreground. Instead, ideological projects are increasingly being implemented. I would like to see a rethink at VBZ - or another operating company.