[Bldg-sim] Unsual Auxiliary Energy Consumption for LEED baseline model.

[Ioannis Rizos]

Dear community,

I’ve just finished some LEED Energy Modelling for a building in Sao Paulo and I came across some results that made me a bit sceptical. I would greatly appreciate your thoughts on the matter.

Description of the model:

Our proposed building has 30% less Energy Demand than the Baseline building.
The proposed building uses a fan coil system with minimum fresh air provision. The baseline model utilises a PFP VAV system (no.8 according to ASHRAE classification).
Fresh air flow rates between Baseline and Proposed buildings are the same – i.e. around 7.5l/s/p.
Both Buildings have heat recovery and similar SFPs.
The proposed building uses a rather mediocre Air Cooled chiller – COP of 2.8 -  whilst the baseline building uses a highly efficient Water Cooled Chiller – COP of 5.5.

The problem:

The proposed building’s auxiliary energy Consumption is around 80kWh/m2, whilst the Baseline’s  auxiliary  energy consumption is  around 400kWh/m2 – i.e. 500% more. Does this sound normal? What kind of auxiliary energy consumption (kWh/m2) is reasonable for a VAV system with PFPs doing 7.5l/s/p fresh air? Of course there will be some recirculation from the economiser, but can this justify 5 times more energy spend on auxiliary?

Regards
Ioannis



Ioannis Rizos
Environmental Consultant

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