Commissioning-orientated building loads calculations. Application to the CA-MET building in Namur (Belgium).

The parallel use of whole building simulation and monitoring of building energy
consumptions (heating, cooling, lighting and other electricity consumptions) represents a
potential “high-level” commissioning tool in order to verify, either as a one shot campaign or
as a continuous process, the correct operation of a building. The most advanced approaches
use on-line building simulation to continuously compare the real performance of the building
to a base line provided by simulation.
In that context, different levels of building loads calculation can be used, ranging from rough
methods like eg degree day methods to detailed multizone building simulation. The former
methods use aggregated information about the buildings (“global” parameters like the heat
loss coefficient for instance) and provide as outputs average quantities (energy consumption
for a given average controlled temperature) while the latter require a high number of
parameters and deliver very detailed results (hourly evolution of demands in each zone of the
building). A major question concerns the suitability of the different approaches in a
commissioning context.
This papers illustrates the use of different calculation methods (heating and cooling loads) for
the particular case of an office building located in Namur (Belgium), which is the object of an
intensive re-commissioning activity for several years. Very global methods are used as well as
detailed computer simulations using TRNSYS Multizone building types 46 and 56. In the
latter case, the model is calibrated using reference periods and can serve as a baseline
indicator of the energy consumption in the building. The complexity of the building (300 m
long, modular architecture, presence of an atrium-like internal street) required some
simplifications in the modelling associated to a specific methodology to extrapolate the results
got from the simulation of a relatively small part of the building to the whole picture.
The paper will explain the advantages and disadvantages of each approach, the required
information and the limits of the results. The potential use of the different calculation levels
for the implementation in a continuous commissioning process will be examinated as
conclusion of the work.