Page 116 - Tussen binnenstad en spoor - Leuven 2003

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RENEWABLE ENERGY SOURCES The suitability of
the site for seasonal thermal storage in the ground
was analysed thoroughly. This technique consists of
withdrawing heat from the subsoil during the
winter (or in other words: storing cold in the sub-
soil), and using this cold to cool the building
during the summer.
Two elements made this option fail:
- the soil conditions required a large number of
relatively shallow boreholes and consequently,
financially unsound, high investment costs;
- the energy measures for the building envelope
created an energy demand profile for which the
balance between winter heat extraction and
summer cold extraction was insufficiently balanced.
Rectifying this imbalance undermined the energy
return.
__ COMFORT
Striving for low energy consumption cannot be at
the expense of user comfort. The design team con-
sequently placed a strong emphasis on passive
climate techniques to combine user comfort with
minimal energy consumption:
- use of daylighting;
- (increased) hygienic ventilation rate for optimal
indoor air quality;
- use of the construction’s thermal capacity;
- possibilities to influence comfort parameters
locally.
DAYLIGHTING Daylighting entry in offices gives a
pleasant feeling of contact with outside, a lively
atmosphere, a reduction in energy consumption
for artificial lighting. However, blinding when oper- was designed to allow better use of the thermal
ating VDU’s must be prevented under all circum-
stances. Optimal utilisation of daylighting assumes
maximal dimming of artificial light in the façade
areas: on overcast days with open or raised solar
blinds, on sunny days also with closed blinds. By
including atria the length of façades with glazing is atrium;
considerably increased despite the large building
depth.
The design team implemented a ’multiple skin’
façade with broad possibilities for adjusting day-
light and sun availability. This flexibility must allow Until recently the assessment of the thermal quality
the user to act actively on changing external
weather conditions, on variable requirements for
daylighting and temporary requirements for the
visual inside-outside and outside-inside relation.
Wooden sliding frames that slide behind one
another are placed on the exterior office façades.
These panels are closed automatically, but users of
the building can reopen the solar blinds if desired.
A rising wooden solar blind with adjustable hori-
zontal lamellae is placed on the atrium side of the
long atrium office façades. This blind is manually
operated. There is an automatic mobile external
sunscreen on the atrium façades and roofs.
INDOOR AIR QUALITY In order to be able to guar-
antee optimal indoor air quality, the office floors
are provided with fresh airflows of 60 m3/h per
person for an occupancy level of 10 m2/person.
These provisions correspond with the highest
indoor air quality classification IDA 1 (pr EN 13779).
Two design measures make it possible to limit the
energy consumption linked to
this comfort choice:
- the air from the office towers is used as
secondary air in the atria via overflow;
- heat recovery from the ventilation air is realised
through high return regenerative accumulators.
USE OF THE THERMAL CAPACITY OF THE
CONSTRUCTION The thermal capacity of the con-
crete construction has a considerable effect on mit-
igating the rise of the inside temperature during
the peak summer periods. An open lowered ceiling
capacity of the concrete construction.
LOCAL CONTROL OPTIONS To increase user satis-
faction local climate control options are provided:
- opening windows in the interior façades onto the
- individual operation of daylight control blinds on
the interior façades onto the atrium;
- limited size of control areas of climate ceilings.
__ ENERGY PERFORMANCE
of a building was only based on the thermal insula-
tion quality of the building envelope. A consensus
has developed both at a European and interna-
tional level concerning the energy performance
approach to buildings. The thermal insulation
quality of the building envelope still remains
important in this, but attention is also paid to the
energy consequences of ventilating, cooling, solar
gains and lighting. The approach is already well
integrated into the energy legislation in our neigh-
bouring countries and will also be included in
Flemish legislation.
The energy performance approach takes the inter-
action of the different energy flows in a building into
account in an integral way. This makes this method
the tool par excellence for assessing the impact of
very diverse design measures on the primary energy
use of a building and to weigh them up.
We will discuss a few crucial aspects:
- functional zoning and buffer zones;
- thermal quality of the building envelope;
- controlling solar gains;
- thermal aspects of the HVAC equipment;
- process-linked energy consumption.
FUNCTIONAL ZONING AND BUFFER ZONES
An essential assumption with rational energy use
for lighting and climate control (heating, cooling
and ventilating), is the limitation of the operation of
building systems to places and times during which
this is required. Functionally the aboveground parts
of the building consist of flexible office floors,
conference rooms for internal or mixed use and a
restaurant. The functionality for these functions is
very different in time and space.
The offices and conference rooms for internal use
are characterized by a fixed timetable. The spatial
organisation of individual offices, open-plan offices,
concentration workstations, meeting areas,
conference rooms… is variable however and the
partial functions are relatively interchangeable.