I am using IES VE to model hotel type rooms that each have a separate bathroom. The bathrooms do not have any heating equipment, cooling equipment or thermostats in them. But they have exhaust system which exhausts at about 8 ACH with the make up air coming from the conditioned adjoining apartment. This makes the bathrooms 'indirectly conditioned'.

The set point for the conditioned apartment is 24 Celsius, so obviously the make up air into the bathroom is at around this temperature. Given that there are some heat loads from lights etc in the bathrooms, the space will obviously end up at a temperature above 24 C.

My question is - in terms of calculating the 'unmet hours', these bathrooms will often fall outside the temperature setpoint for the main rooms. Increasing size/flow rates of the air conditioning equipment in the main rooms will not assist in achieving this, as the main rooms are maintaining temperature already.

Do I need to:
1. Exclude these bathrooms etc from the 'unmet hours' calculation as they are not directly conditioned to maintain a setpoint temperature.
2. Model these bathrooms with baseline air-conditioning equipment in both the proposed and the baseline model so that they are able to maintain temperature even though this does not represent what will be really implemented. (There is something in the reference guide about using a baseline system if no heating or cooling plant is proposed for a space, but I have currently presumed this refers to a whole building or a whole area rather than an individual room within a building.)
3. Change the model thermal zoning to include the apartment and the bathroom as a single thermal zone so that the model mixes the air completely across both the apartment and the bathroom and thus maintains temperature in both spaces. The problem with this is that the proposed equipment sizing may not cover all of the load in this now larger space, in which case the whole space may struggle to maintain temperature.

In Australia, we would use option 1 for our modelling, but I can't find anything in the ASHRAE 90.1 that describes this. Your help is much appreciated.