Hotel ventilation should be regarded as an integral part of a hotel’s energy solution. The requirements of individual rooms must be carefully examined – reception, kitchen, dining room, swimming pool and hotel rooms – and the ventilation, heating and cooling requirements of each space precisely dimensioned. The key factor: the hotel energy system should not be over-dimensioned, as this can unnecessarily generate a (very) high investment and monthly costs for the hotel manager. It is also important not to under-dimension the energy system, as this can reduce room comfort. This can cause room conditions to become either too hot during summer or too cold during winter, or failure to supply fresh air into the rooms… All these affect the satisfaction of guests and impact their hotel evaluation, as well as their decision whether to return to the hotel or choose a different one.