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Case Study Summary
Belgium - BE1
PROBE Renovated Building, Limelette
Building Description
The PROBE-building is a renovated
office building located on the test site of
the Belgian Building Research Institute
(BBRI) at Limelette in a rural and very
quiet environment. The main façades of
this two-story building are west and east
oriented. About 30% of the façade surface
is glazed. The exterior walls are noninsulated brickwork cavity walls and the
building has a flat roof. The interior space
is subdivided into cellular offices on the
west and east sides of the building. Each
office has exposed plastered ceilings and
internal walls consisting of heavy
brickwork. Illustrations of the building
and floor plan are presented in Figures 1
and 2 respectively.
Figure 1: The PROBE Building
PROBE stands for Pragmatic Renovation
of Office buildings for a Better
Environment. The main objectives of the
renovation were the reduction of energy
demand and the improvement of indoor
thermal comfort in both summer and
wintertime. The most important
renovation measures were the:
• installation of a new fuel boiler,
thermostatic radiator valves and
improvement of the regulation
system;
• replacement of the old roofing
combined with additional roof
insulation;
• installation of a mechanical
ventilation system with infrared
presence detection;
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10
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•
replacement of the single glazing
with low-e gas filled double glazing.
(central U-value = 1,1W/m²K);
• installation of external solar shading
with automatic control;
• installation of large grilles for night
ventilation;
• replacement of the existing artificial
lighting by low energy lighting
incorporating luminance control and
electronic ballast.
These renovation activities were
undertaken on a step by step basis thus
minimising office disruption. All these
measures were regarded as relatively
small-scale improvements and of the type
that can be applied to many similar office
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16
4
3
2
17
14 m
8
7
N
6
5
40 m
Figure 2: Floor Plan Showing Offices Monitored
Architect:
Ventilation design:
Research team:
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buildings without complex or detailed
planning studies. For this reasom the word
‘pragmatic’ appears in the acronym
‘PROBE’.
The Walloon Region and several
industrial partners have funded the
refurbishment of the PROBE-building.
Ventilation Philosophy and Aims
The building has two ventilation systems
with totally different objectives covering
air quality ventilation and summer cooling
(see Figure 3).
Air Quality Ventilation: Air quality is
maintained using an infrared controlled
mechanical ventilation system. Fresh air
is mechanically supplied into each office
at 25 m³ per hour and per person. and is
extracted from the toilets. Every office has
its own infrared presence sensor which
restricts supply ventilation to periods in
which the office is occupied. This leads
to a reduction of ventilation losses of
35%. Airtight ductwork and a well-regulated fan are important conditions for the
proper operation of this system.
Intensive Night Ventilation: For night
cooling in summer, high rates of natural
ventilation is developed by means of
large grilles located on both sides of the
Y. Wauthy, Brussels (Renovation)
BBRI, Brussels
BBRI, Brussels
NatVent
Case Study Summary
Ventilation of the PROBE-building
SUMMER
Daytime:
infrared
controlled
mechanical
ventilation
Nighttime:
intensive
natural
ventilation
WINTER
Daytime:
infrared
controlled
mechanical
ventilation
Nighttime:
no
ventilation
Figure 3: Schematic of Ventilation Strategy
building. The objective of this intensive
ventilation is to cool down the internal
mass of the building with cold external
air. By cooling the mass, improved daytime thermal comfort can be achieved.
Ventilation Technology
The major problem of the existing
building was overheating in summer for
which a possible solution is the
installation of active cooling. However,
as low energy use was one of the starting
points of the renovation project, an overall
strategy of several passive measures was
chosen to tackle the problem of
overheating.
The reduction of direct solar gains
through glazed surfaces was regarded as
one of the most important steps toward
accomplishing a comfortable indoor
summer climate. To achieve this, vertical
external screens, through which only 15%
of solar radiation passes were installed on
Figure 4: Solar Protection/Grilles
(East)
the west side of the building Figure 6).
Despite their efficiency, they are
transparent from the inside. On the east
side of the building, inclined screens were
installed to reduce the solar gains (Figure
4). A small meteorological station on each
façade controls the shading devices
according to prevailing solar radiation,
wind, rain and temperature conditions.
Besides reducing direct solar gains the
screens also eliminate glare. Heat gain
through solar radiation was reduced by
63% by insulating the roof with 10 cm of
glass wool.
An important effort was made to reduce
internal heat gains. This involved
reducing the installed lighting power of
the offices from 22W/m² to 9.5W/m² . In
addition integrated luminance sensors
were used to dim the lighting near the
windows according to the luminance level
on the desks. These new energy efficient
luminaires also improved the visual
comfort the offices.
In addition to reducing heat gains,
intensive night ventilation, to cool down
the internal mass of the building, is
applied to improve summer comfort.
Night cooling was possible because the
internal mass of the building is accessible
to the flows of cold external air.
Especially exposed in the PROBEbuilding, is the internal mass of the
concrete floors and ceilings. In addition
the internal walls are made from heavy
brickwork. Hence the building has an
especially large quantity of accessible
thermal mass.
The intensive night ventilation concept is
based on the principle of natural cross
ventilatio (Figure 5). To achieve this, large
ventilation grilles were installed on both
sides of the building. On the east façade
of the building, the existing wooden
window frames were kept and large
ventilation grilles were placed in front of
the openable part of the windows. These
ventilation grilles can be removed outside
the summer season. For the sake of visual
Figure 5: Cross-Ventilation Principle
effect, the ventilation grilles were light in
colour.
On the west side of the building, new
aluminium window frames were installed.
These contain two openable parts with a
fixed ventilation grille. The openable
parts are opaque and well insulated.
Although this was a more expensive
solution it had the advantage of having
ventilation grilles on both sides of the
window. The impact on the visual comfort
in the office is limited.
Figure 6: Solar Protection and Large Grilles (West)
These ventilation grilles contain an insectgauze and meet high performances on rain
tightness. They are also burglarproof. As
intensive ventilation only takes place at
night, there are no special requirements
concerning to noise and draught. For
correct operation the grilles have to be
opened manually and internal doors must
be left open during the night to allow
cross-ventilation. In this office building
there are no privacy or security problems.
30.0
3000
25.0
2500
20.0
2000
15.0
At the beginning of the monitoring
campaign, the renovation works had not
been completed. On the west of the
building there was still no solar protection
and only office 3 and 6 were ventilated
intensively at night by opening the
windows. As there were no windows open
on the west of the building, night
ventilation during the monitoring
campaign was based on natural singlesided ventilation instead of crossventilation.
Summer Monitoring Results
Figure 7 illustrates some of the monitoring
results. Office 3 and 4 are located at the
east (see Figure 2) and have very similar
internal gains; namely two people and two
computers. Office 3 was intensively
NIGHT VENTILATION in
OFFICE 3
10.0
1000
5.0
500
Monitoring Programme
During the summer of 1997 a monitoring
campaign was held in the building to
evaluate the effect of the different
renovation measures on thermal comfort
in summer. Monitoring was focused on
the offices on the east side of the first floor
(office 3-7, see Figure 2). Internal
temperatures, surface temperatures, air
flows, etc. were measured.
1500
NO NIGHT VENTILATION in
OFFICES
0.0
global horizontal solar radiation (W/m²)
Case Study Summary
temperature (°C)
NatVent
0
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Off.3
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Off.4
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Off.16
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Text
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Glob. horiz. solar rad.
Figure 7: Summer Monitoring Results (1997)
ventilated at night starting from 18th July.
Office 16 is located on the west of the
building. This office had no shading
device and has quite low internal gains
(one person and one computer).
A comparison of the temperatures of the
offices on the east (office 3 & 4) and the
west (office 16) side of the building
proves the importance of solar protection.
Direct solar gains caused peak
temperatures that were up to 3°C higher.
The night ventilation of office 3 had a
clear effect on the thermal comfort. The
internal temperatures were found to be
lower and more dynamic when night
ventilation was applied. The ventilation
flows at night were monitored by means
of tracer gas measurements. Although, at
this stage, ventilation was largely singlesided, the driving forces developed
mainly the stack effect resulted in
measured air changes of between 0.5 and
2.5 ach. Detailed measurements show a
clear relationship between the air change
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rate and the indoor-outdoor temperature
difference.
To understand the working of the thermal
mass a heat flux meter was installed on
the ceiling surface of office 3. The
measured fluxes are given in Figure 8a.
Positive values indicate a heat flux from
the ceiling to the zone. The corresponding
internal and external temperatures are
given in Figure 8b. There is a clear link
between the application of night
ventilation and the heat flux through the
ceiling surface. Before the application of
night ventilation the thermal mass of the
ceiling is not activated. The variations of
the heat flux through the ceiling surface
are rather limited. Due to the night
ventilation the mass of the ceiling is used
as a thermal buffer. During a moderate
period (PHASE 1 – Figure 8a) the ceiling
released the heat that had accumulated in
the thermal mass, while during a warm
period (PHASE 2 – Figure 8a) the ceiling
absorbed some of the heat in the zone.
30.0
Off.3
Off.4
Text
15
PHASE 1
NO NIGHT VENTILATION in
OFFICES
25.0
temperature (°C)
heat flux (W/m²)
10
5
0
20.0
15.0
-5
PHASE 2
10.0
NO NIGHT VENTILATION in
OFFICES
-10
NIGHT VENTILATION in
OFFICE 3
-15
10/7/97
NIGHT VENTILATION in
OFFICE 3
5.0
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16/7/97
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time
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Figure 8a &8b: Relationship between Air Change Rate and Temperature Difference (1997)
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Case Study Summary
The measurements show that during the
monitoring period there is a maximum
heat flux of 10W/m² from the zone to the
ceiling. This value can be doubled, if the
thermal mass of the floor is also
accessible. This means a total peakcooling source of 480 W for a standard
office in the PROBE-building. This value
could be increased by higher rates of night
ventilation. Higher rates could probably
be realised by adopting cross-ventilation
instead of single-sided ventilation.
It is however clear that the buffer
capacities of the ceiling and the benefits
of night ventilation are limited. It is not
possible to achieve a good indoor summer
comfort without other measures like solar
protection and reduction of the internal
gains.
During warm periods the openings for
natural ventilation have to be opened
manually in the evening. During daytime
the large grilles have to stay closed,
especially when the outdoor temperature
rises above the internal temperature.
Therefore the concept depends strongly
on the behaviour of the occupants. Clear
information is a crucial element in the
success of the proposed ventilation
strategy.
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25
temperature (°C)
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15
T_ext
10
Off_16
Off_15
5
Off_13
0
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Figure 9: Monitoring Results of Completely Renovated Building (1998)
Conclusions
The first monitoring results show that
there is an important improvement in
thermal comfort due to the different
refurbishment measures. These results are
also confirmed by the positive reactions
of the occupants. Moreover one has to
bear in mind that during the monitoring
period not all the refurbishment works
were completed; shading devices were
only installed at the east side of the
building and only office 3 and 6 were
ventilated at night. One can expect better
results after the completion of the
renovation project.
Figure 9 show the first monitoring results
of the completely renovated building
(May 1998). During a warm period the
internal temperatures remained below
27°C while the outdoor temperature rose
to 31°C.
The PROBE-building demonstrates how
small-scale and rather simple
refurbishment actions can improve the
summer comfort of an existing office
building. Only the total effect of all the
different actions together results in an
acceptable indoor comfort.
NatVent NatVent NatVent NatVent NatVent NatVent NatVent NatVent NatVent NatVent
The NatVent Project
The NatVent Partners
European Joule Project
Natvent is aimed at reducing energy
consumption and carbon dioxide
emissions by developing and
demonstrating natural ventilation
solutions. This project is targeted at
climates in which overheating can be
avoided by good architectural design and
by minimising internal heat gains. By
introducing natural ventilation, the
complexities of mechanical systems and
associated energy demand is eliminated,
while the need for air conditioning is
minimised. These case study summaries
are intended to provide innovative
examples of the use of natural ventilation
and to demonstrate performance, pitfalls
and solutions.
Project Partners are:
Belgium: Belgium Building Research
Institute,
Denmark: Danish Building Research
Institute,
Netherlands: TNO Building
Construction and Research, Delft
University of Technology,
Norway: Norwegian Building Research
Institute,
Sweden: J&W Consulting Engineers
AB,
Switzerland: Sulzer Lab,
United Kingdom: Building Research
Establishment, Willan Building
Services.
NatVent is a Joule project undertaken
with part funding from the European
Commission in the framework of the Non
Nuclear Energy programme.
For further information contact:
Jan Demeester, Belgium Building Research Institute, Rue de la Violette 21-23, 1000 Brussels, Belgium
Tel: +32 2 655 7795
Fax: +32 2 653 0729
e-mail: [email protected]