Page 117 - Tussen binnenstad en spoor - Leuven 2003

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The climate control and lighting systems are
consequently divided into small control zones.
Heating and cooling are provided by hydronic
cooling ceilings with a maximum cooling capacity
of 60 W/m2. For areas with higher cooling loads
the cooling ceiling is supplemented by floor
ventilo-convectors.
The conference rooms for mixed use and the
restaurant are used very intermittently. They are
clearly spatially defined and cannot easily be
moved to another part of the building due to the
technical provisions. For these functions the con-
trols for the cooling, heating and ventilating equip- demanding functions. The passive comfort meas-
ment are designed so that the periods of use and
the number of users can be optimally anticipated.
The atria are conceived as buffer zones in which no
permanent workplaces are located. The climate in
the atria is only roughly conditioned:
- at low winter outside temperatures the atria are
heated up to 16°C by means of a floor heating
system. Draught along the vertical glazing is lim-
ited. On the railway side this is realised by pro-
viding glass balustrades on each level on the
gangways. A glass interior façade is provided on
the ring road side.
- during hot sunny periods the inside temperature
in the atria is limited through solar blinds on all
glazing panes and by means of intensive natural
ventilation with outside air. This means that both
the vertical windows on the ring road side (at the
atrium floor level) and the horizontal sliding win-
dows in the atrium roof are opened. A control
algorithm was developed to adjust the opening
angle of the vertical windows and the width of the
opening in the atrium roof so as to obtain the
optimal ventilation rate in function of the inside
and outside temperature. Opening the windows
does mean that noise pollution enters the atrium.
The natural ventilation is also accompanied by
uncomfortably high airflow speeds near the vertical
windows. To limit noise pollution and draughts
insofar as possible a glass interior façade is placed as high-temperature coolers for the climate ceilings
(also see winter situation) at the vertical windows.
Thanks to the natural ventilation, the solar blinds
and a limited floor cooling system, a climate is cre- Air treatment is limited to fresh airflows required to
ated in the atrium in which the comfort tempera-
ture in the occupancy zone during working hours
does not exceed 25°C over more than 150 working
hours per annum and 28°C over more than 35
working hours per annum. These design interven-
tions mean that the atria are unsuitable as a per-
manent workplace: they do not fulfil the thermal
and acoustic comfort requirements at all times.
The addition of the glass interior façade and the
natural ventilation possibilities are passive comfort
measures that ensure that the atria can be used
during the majority of the year for less formal or
ures and the surrendering of the office functionality (central and distributed network infrastructure,
on the coldest and hottest days do ensure that the
primary energy consumption of the building (in
energy performance terminology) is 17% lower
than would be the case with full air conditioning in
the atria.
BUILDING ENVELOPE The width/height-propor-
tions of the atria are a compromise between
increasing the daylight availability and limiting the design the target value for the EPC-figure was 1.5
heat-loss area of the atria. Despite the high per-
centage of glazing, and despite the increased loss
of heat through the floor over the bicycle parking
rack at external climate conditions, the building
achieves a K40 (NBN B62-301) general level of heat
insulation.
THERMAL ASPECTS OF THE HVAC EQUIPMENT
Heat generation is realised by two preferential
condenser gas boilers with a 900 kW capacity,
and a non-preferential high return 1750 kW low
temperature boiler. Cold generation is realised
through three refrigeration compressors (total
capacity 4 MW, including cooling equipment
for the IT-infrastructure) that supply ice water at
a higher temperature to the cooling ceilings,
and ice water at a lower temperature to the
ventilo-convectors. The cooling towers are used
during appropriate weather conditions to act
without the intervention of the refrigeration
compressors.
realise the requested indoor air quality. The energy
required for the distribution of heat, cold and fresh
air is limited in this way together with the optimisa-
tion of the SFP-value (specific fan power) and good
pump controls. High return regenerative accumula-
tors are used for heat recovery in the air handling
units for the office floors. The results of the analysis
are incorporated in the specifications for the instal-
lation components.
PROCESS-LINKED ENERGY CONSUMPTION The
building owner’s IT-team was supported in formu-
lating the energy aspects of the office equipment
servers, telecommunications equipment and PCs).
A correct estimate of the heat load from office
equipment taking the uncertainty of future devel-
opments in information technology into account, is
an important aspect for the functional sustainability
of the building.
ENERGY PERFORMANCE At the beginning of the
(NEN 2916). This corresponds with the maximum
value for new office buildings recently imposed in
the Netherlands. The EPC-figure for the prelimi-
nary design of the building is 1.7.
Three elements form the basis for this limited sur-
passing of the target value:
- the fresh airflow is 60 m3/(h. person), which is 50%
higher than normal in standard offices;
- the high glazing percentage of the façade;
- the application of seasonal thermal storage in the
ground was not financially and technically fea-
sible.
Our experience has shown that the EPC-figure in
Flemish building practice fluctuates between 1.8
and 2.2.