Dear All,

We are currently modelling a CI project. The base building is 10 stories high and is served by a central HVAC plant with 2 existing chillers (1 of them will be replaced by a new one) and new boilers. Ventilation is based on a floor by floor DOA unit.

  1. an underground floor with a restaurant, a bar, kitchens and technical areas (out of scope of work);
  2. a ground floor with the entrance (in the scope of work);
  3. 7 upper office floors (in the scope of work);
  4. a top floor with technical areas (out of scope of work)

The scope of work will include alterations in the lighting system, HVAC fan coils (for areas within the scope of work) and the replacement of 1 of the 2 existing chillers (that supply the entire building) and new boilers – other works are not relevant for simulation purposes.

After reading the Reference Guide for LEED v4: ID+C – Commercial Interiors I still have some doubts on how to accurately model both the Proposed and Baseline buildings. Please confirm if the following assumptions are correct:

  1. Since not all of the building is to be certified (only the ground floor and the 7 office floors are under certification), the areas out of the scope of work shall be modelled with adiabatic walls/pavements (those that are in contact with the spaces under certification) and without lighting, plug loads and HVAC systems;
  2. Envelope: the envelope will not be changed (existing conditions)
    1. Proposed: modelled as is;
    2. Baseline: modelled as per Appendix G of ASHRAE 90.1 – 2010 as New Construction
  3. Lighting: the lighting system within the scope of work is being improved and shall respect minimum requirements under section 9.4;
    1. Proposed: modelled based on the lighting plans;
    2. Baseline: modelled as per tables 9.5.1 (building area method) as New Construction
  4. HVAC: the HVAC terminal units and the DOAs are being replaced and shall comply with minimum requirements of ASHRAE 90.1 – 2010. New boilers and chiller shall also comply with minimum requirements (but not the existing chiller).
    1. Proposed:
      1. Air-side: Model based on HVAC plans;
      2. Water-side: Model based on the HVAC plans and existing equipments, but with adjusted parameters for Electric Power and Cooling / Heating capacities based on Method 2 of “Contribuition of Base Building HVAC and Service Water-Heating Systems” section of the Reference Guide.
    2. Baseline:
      1. Air-side: Model based on number of floors, energy type and predominant condition for the whole building (including areas that are out of the scope of work) as per Appendix G;
      2. Water-side: Number and type of chillers based on peak thermal load (areas under certification only) and boilers based on conditioned floor area. NOTE: the existing chiller in the Proposed design shall not enter into account for the baseline building, as the baseline shall be modelled entirely as New Construction for all systems (envelope, HVAC, Service Hot Water (SHW), lighting, etc..))

NOTE: I am aware of LEED Interpretation 10454 that allows the baseline building to be modelled with the existing envelope prior to any work being subject to revised percentage improvements thresholds for both credit and prerequisite. However the allowance to maintain the existing conditions applies only to the envelope and not any existing systems that weren’t replaced (lighting fixtures, HVAC equipment (central and local equipments), etc..)

Thanks for your attention.