Do I need to model unheated spaces?

In general, you do not need to model unheated spaces. All rooms included will be added to the total heat loss calculation and therefore the heat pump will be sized against this. Therefore, including unheated spaces could lead to oversizing the heat pump. Its therefore, better to exclude unheated spaces in most cases, for example garages and conservatories. Instead, you should specify the parting wall between the heated and unheated space. 

However, some unheated spaces should be included for practicality, for example internal store rooms. Rather than leaving a gap in the floor plan, rooms like this should be included. In line with MCS, Heatpunk includes a room type for this scenario (Store).