Hi all,

I've been searching around the LEED V2009, V4 and V4.1 EAp2 / c2 versions trying to find an answer to this problem, but I've encountered little information on how to model natural / mixed mode ventilation.

I'm currently modelling a mix mode ventilation building that works in the following way:

1) Automatic operable windows opening per CO2 sensor levels or temperature sensor (opens if temperature rises above cooling setpoint and outdoor temperature is below room temperature (with 16ºC minimum to avoid thermal discomfort));

2) Mechanical design: Monozone Mechanical Ventilation Heat Recovery (MVHR) for ventilation and FCU (ccoling or heating) or radiant heat floors (heating only) to maintain comfort conditions;

Proposed Design:

Thermal comfort: FCU and/or radiant floor cycle ON and OFF to maintain thermal comfort conditions as per the design setpoints;

Ventilation: Automatic windows open and close as per the above mentioned criteria. When windows are open, MVHR is OFF, when windows are closed and room occupied, MVHR ON;

Comfort analysis - demonstrate thermal comfort levels as per ASHRAE 55 - 2017 on a full year (PPD and/or PMV);

To account for any savings, 2 sets of Proposed Design simulations are made: (1) no natural ventilation (mechanical ventilation only) and (2) with mixed mode ventilation as described above. This enables the project to demonstrate energy savings in ventilation and cooling by an ECM and also demonstrating that comfort levels are maintained on a full year as per ASHRAE 55 - 2017 (PMV / PPD). This strategy is decribed in the Advanced LEED Modelling Guide, Appendix D.1, but it is only binding to LEED V2009.

Baseline: System sizing per ASHRAE 90.1 - 2016 Appendix G and mechanically ventilated and themally treated only (no windows are operable and no natural ventilation).

Would this be a good approach to account for energy savings in ventilated mixed mode buildings for LEED V4.1?

Thank you all in advance!