Natural Ventilation - airflow rates

The standard would be ASHRAE 62.1-2007. The ventilation rate must be identical in both models. In order to claim any savings for natural ventilation see the example in the Advanced Energy Modeling Guide for LEED Technical Manual.

Hello, I am modelling a hotel. Rooms are naturally ventilated. For bedrooms according to Table 6.1 of ASHRAE 62.1-2007 outdoor air rate has to be the sum of 2.5 l/(s*person) and 0.3 l/(s*m^2). Therefore in a room having floor surface of 16m^2 and height of 2.5m and in which two persons are present natural ventilation should be 0.9 ACH. I think that during winter nights a constant ventilation of 0.9ACH would be excessive and unrealistic. Do you agree? In particular during the coldest nights, for the heating system maintaining the setpoint temperature would be difficult. I am not interested in claiming any savings relative to natural ventilation but I would avoid to waste energy because of excessive ventilation.

Yes. You should model the operable windows as they would be used. Do not assume that they are open all winter.