mechanical ventilation problems

[georgenash]

I’ve encountered a problem I can’t explain. A building has split system cooling and underfloor heating. Some area are naturally ventilated and some mechanically ventilated with heat recovery.

I have selected split system as the UK NCM system, and added in the heat recovery efficiency of the MVHR to the system (for the mechanically ventilated spaces). I then apply mechanical supply at room level and set the SFP.

However, when you do this, it drastically reduced the heating energy demand of the Notional building, and has no effect on the Actual building.

This is down to the spaces notional building having there auxiliary ventilation rates and losses reduced.

Any insight would be appreciated, as this does not seem right to me

[VirtualEngineer]

Hi

Is this in VE Compliance ApSim?

Underfloor heating and comfort cooling does not easily fit into the available SBEM / NCM systems. Perhaps instead of trying a split system led type you could try a 'Constant Volume System' ventilation led type.

This way in ApSystems you can put in the boiler as heat source for the underfloor, the reverse cycle ASHP for comfort cooling and the SFP & HR for the MVHR. Not sure what effect this would have, but you could test it and see whether it produces results which are more realistic.

Thanks

VEng