We have a LEED v4 project (office building) were the project team want to use the CEN option for IEQp1 (using EN 15251 instead of ASHRAE 62.1).

Also, for the energy modeling, the Proposed building has DCV based on CO2 concentration. In LEED 2009, when modeling DCV in the Proposed case, the Baseline should be modeled with ASHRAE 62.1 outdoor rate. Is this the same for LEED v4-projects? In 90.1-2010 it i stated that Baseline and Proposed shall have the same ventilation rate unless DCV is modeled, however it does not say what the Baseline ventilation rate shall be for this exception.

We believe, that if we follow EN15251 in IEQp1, maybe the Baseline building should use the min rate of EN15251 when DCV is modeled in the Proposed building.

For example (somewhat simplified): EN15251 states that outdoor air rate should be 10 l/s, person. The Proposed building will be designed with 13 l/s, person. As far as we understand, the Baseline model should then have an outdoor air of 10 l/s, person since the Proposed building exceeds required ventilation. This is probably OK as long as we don´t have DCV?

What is the case with DCV? Do we really have to go all the way down to 62.1 rates?