Dear All,

I am requesting help on the energy modeling protocol for a building both connected to a stand-alone plant and a district energy system.
I read a lot of posts on the forum before posting but I didn’t find an answer matching my project.

Description :
The project consists of building with a total area of around 500 000 sf, treated as a whole in Core and Shell v.2009.
The building includes two different activities : office Spaces (200 000 sf) and retail activities (around 300 000 sf).

Office spaces will be modelled as designed.
The HVAC systems are not known for retail spaces (but the heating and cooling source are), so the Baseline system will be also used for the proposed model (as mentioned in ashrae 90.1 Table G3.1).

Office spaces are supplied by a ground source heat pump, providing around 80% of the annual heating and cooling energy. The energy backup will be provided by purchased energy (heating and cooling DES).
Retail spaces are only provided by purchased energy (heating and cooling DES), as the GSHP could not supply the whole building.

Question :
I read the USGBC Guidance for District thermal energy, but it is assuming the project is only supplied by a DES. Whereas the DES is used as a backup source in my project (for Offices spaces that is).

So my questions are as follows :
- Should I model 2 different systems for Offices and retail space (for proposed and Baseline), as the energy plant strategy is different (purchased energy used as primary source for retail, but as a backup for office spaces)
- How should I model the heating and cooling source of the Baseline(s) ? As purchased heat as suggested in USGBC Guidance, or as Boiler + Chiller (ashrae 90.1-2007 G3.1.1B for hybrid systems)?

Also a “hybrid System” is only defined in Ashrae 90.1-2007 as a mix fossil/Electric. Could it be extended as purchased energy/Electric?

For information , purchased energy is here provided by CPCU and Climespace, which are huge DES providing energy for hundred or maybe thousands buildings in Paris. They use using many plants and energy sources (CPCU use a mix of fuel, gas, waste to energy,…). We obviously can’t have access to the plants characteristics of these DES, thus option 1 of LEED Guidance will be used, in case of modelling the DES.

I would try modelling follows :
Proposed – Office spaces : Model as designed, with GSHP and Purchased heating and cooling as a backup
Baseline – Office Spaces : Purchased energy (and not boilers and chiller as suggested in ashrae 90.1-2007 Table G3.1.1B)

Proposed – retail spaces: Same system as the Baseline (system 7), provided with Purchased energy
Baseline – retail space : Purchased energy.

Sounds It right to you?

Thank you for reading my long post, and I would really be grateful if someone could give me some advice.