Hello,
I am trying to model and events space and connecting offices. I have two separate systems for these areas. The events space (zone 1) is being cooled using the AHU supply air via the ventilation system purely and the offices will be conditioned by a VRF Systems with the terminal units being FCU's.
As the events space will suffer from Solar gain there is a chance that we will have to naturally ventilate the area as well as use the ventilation system for cooling. How would I specify the individual systems in the Part L section on Heavacomp? Would I tick the mixed mode box in the cooling system tab?
Thanks
Hi Matt,
I would firstly advise caution if you are intending to use Part L to determine if natural ventilation is required, as SBEM is not a design tool indicative of real-world conditions. (To see if natural ventilation is required you would need to use design tools such as CIBSE Gain, or if a more in-depth analysis of openable-windows is required then you would need to use Hevacomp Simulator).
In Part L, the mixed mode option would indeed be selected in the event of natural ventilation, however the final say on the HVAC type would need to come from your Assessor Scheme provider. The below info from the iSBEM manual may be of assistance with your selection:
HVAC system uses a mixed-mode cooling operation.NB: “Mixed-mode” refers to a hybrid approach to space conditioning that uses a combination ofnatural ventilation from operable windows, and mechanical systems that include air distributionequipment and refrigeration equipment for cooling. A mixed-mode building integrates the use ofair-conditioning when and where it is necessary, with the use of natural ventilation whenever it isfeasible or desirable, to maximize comfort while reducing the energy use (compared to yearroundair conditioning).
I hope the above helps to clarify, if you need anything else please let us know.
Shane Regan | Principle Building Performance Support Engineer