Has anyone had any experience with hybrid ventilation units such as breathing buildings or monodraught?
If so how have you gone about your ventilation rates and inputting them as you can't guarantee a fixed supply air temperature as they have no heat recovery and are purely mixing (a glorified window essentially).
The only option for steady state calculations in Design Database would be to input the fixed rates as you mention, so perhaps you may need to do some hand calc's and use an appropriate average.
For more complex airflow analysis Hevacomp Simulator would be required, in which you can model Flowpaths (grilles, vents, etc) and Openable Windows. (Note you would need a Hevacomp Simulator license to use this). If you require further details on this I would have a look at the relevant section of the manual, some of which can be found below.
Shane Regan | Senior Building Performance Support Engineer