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Premier’s Visy Industries Environmental Education
Scholarship
Natural Ventilation in Buildings Case
Studies and Design Guide
Annette Henriksen
TAFE NSW - Hunter Institute
Sponsored by
Introduction
Globally there has been a growing awareness that a re-think on how energy is used is
needed. This has been generated by increasing energy prices, primarily oil, and the
acknowledgment that the increase of carbon dioxide in the atmosphere is contributing to
a global warming. Increasing pressure has been placed onto energy consumers, designers
and governments to acknowledge the effect of energy use on the environment and to
present energy efficient designs and products. Concepts such as sustainability, depletion
of non-renewable resources, product life cycle analysis, recycling and energy efficiency
must be considered.
One area where significant energy is used is in the lighting, heating and cooling of
buildings. Australia is comparable with Europe with approximately 40 per cent of energy
use being by the commercial building sector. A report commissioned for the Australian
Greenhouse Office in 1999 found that heating accounted for 33 per cent of Australian
commercial building energy use, lighting 15 per cent, cooling 21 per cent and ventilation
16 per cent, a total energy use of 85 per cent 1. Further it is projected that the
greenhouse gas emissions from the building sector will approximately double between
1990 and 2010 1.
Natural and hybrid ventilation, use of shading devices, building materials and window
placement all have significant impact on the building energy use. This report considers
some case studies showing the incorporation of these strategies into building design.
An Overview of Natural Ventilation
Natural ventilation uses no mechanical assistance, but relies on temperature and air
pressure differences in and around the building to develop air flow within the building.
It has been found that once the air temperature reaches 35C, natural ventilation is
ineffective for internal building cooling. Hybrid ventilation uses mechanical equipment,
predominantly fans, to assist in natural ventilation when required. Natural ventilation in
buildings has three uses during the daytime hours. These are to cool the indoor air
temperature, cool the structure (thermal mass) of the building and to cool the human
body. Air moving over the body allows cooling through evaporation, and reduces the
perceived temperature. At night natural ventilation is used to cool the structure (thermal
mass) of the building.
Archaeological Museum of Delphi, Greece
The original museum was built in 1903, and has since undergone four modifications,
with the last retrofit in 2003. The latest retrofit and modification aimed to improve the
internal air quality and temperature, light and acoustics. The Greek architect,
A N Tomabazis’ design philosophy was to use natural light and ventilation with artificial
lighting and mechanical ventilation systems as a backup. In summer, temperatures up to
32C had been recorded within the building and the heating and ventilation systems were
unable to cope with the fluctuations in peak visitor numbers. While the museum had
been designed for natural ventilation and good daylighting in previous additions and
modifications, poor window placement and shading had resulted in unwanted internal
heat gain and direct solar glare5. This shows that optimal design is often complex and
requires good comprehensive design from the initial design stage.
The principal bioclimatic modifications made to the museum in the 2003 retrofit were:
 Provision of 5 cm thick extruded polystyrene foam boards to the walls
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All windows were replaced with new double glazed windows, controlled by a central
BMS. Approximately 50 per cent of the windows are able to be opened.
New external shading was provided to the windows.
Light diffusing ceiling over the Siphnians Treasury hall
Daylight lantern and light slots over the Charioteer room.
Addition of ceiling fans and light reflecting ceilings
Siphnians Treasury and Hall of the Charioteer
A light diffusion ceiling is used in the Siphnians Treasury. An upper level roof allows
indirect daylight to enter, through carefully placed louvres. The light is then transmitted
down through the waffle gridlike structure to the room below. A light lantern was
designed for roof of the Hall of the Charioteer, which would allow indirect natural light
to enter through reflection onto a central prism. The arrows in the diagram below left
show how the light enters through the roof skylight and is reflected onto the central
prism. No direct natural light is able to enter the room, reducing glare and heat in the
room.
Far left and left:
Diagram and
photograph showing
the transmittance of
light into the
Charioteer room.
The arrows show the
light path through the
roof skylight and
reflection onto the
central prism.
(Diagram source: [2])
Modelling and BMS Monitoring
In order to confirm the architectural design concept for the 2003 retrofit, extensive
thermal and daylighting studies were performed by the Department of Physics at the
University of Athens using computer analysis programs and 1:20 scale models under an
artificial sky and heliodon. The BMS monitoring has shown significant energy and cost
savings and that good thermal performance and lighting is being achieved. An energy
audit has shown that energy use has decreased from 302 kWh/m2 to 117 kWh/m2 after
the retrofit.
Papageorgiou Foundation General Teaching Hospital,
Thessaloniki
Designed using bioclimatic principles and constructed during the 1990’s, the General
Teaching Hospital is sited on an open unvegetated hill slope overlooking the motorway
outside the city of Thessaloniki. The Hospital has seven floors of medical departments,
diagnostic, therapy and nursing units with a central three storey atrium entrance area. It is
expected that the Hospital will have a yearly energy consumption of 156 kWh/m2,
compared with the mean value in Greece of 407 kWh/m2 4.
Left: Model of the
hospital showing the
triple “L” nursing wings
to the top right hand
side. The Medical
departments and
courtyards are to the
bottom left hand side.
The entrance atrium is
located to the centre,
front covered entry to
the bottom centre and
auditorium to the bottom
right hand corner
(Source: [4])
Entrance Atrium and Medical Department Courtyards
The three storey main entrance atrium is daylight with linear roof skylights with okalux
glazing on both vertical sides and high level glazing. Courtyards have been used to divide
the depth of the building in the Medical Department rooms to allow for good daylighting
and ventilation of the rooms. The courtyards are shaded using pergolas and deciduous
creepers and re-entrant windows within the walls are used to control daylight and solar
heat.
Daylighting and Thermal Studies
Daylighting studies of the nursing wards and main entrance atrium were carried out at
the Martin Centre, University of Cambridge using scale models under an artificial sky
simulator and heliodon. Mathematical and computer modelling was also undertaken4.
During construction one of the nursing rooms was fitted with the shading devices and
monitored and results compared to the model and mathematical studies.
Mechanical Ventilation
In the areas that do not require air conditioning, such as offices and patient rooms, a preconditioned fresh air supply system is used to maintain a temperature of less than 30C.
The comfort temperature has been extended up to 30C by the use of ceiling fans. Air
handling units pre-condition the external air and exhaust fans are used to discharge the
air. During the night, when the external temperature and humidity are lower than the
internal, external air is used to pre-cool the hospital4.
Meletitiki Office Building, Polydroso (Athens)
This three storey 8 m wide by 35 m long office building has been purposely built for and
architecturally designed by Meletitiki A N Tombazis and Associates, Architects with
bioclimatic design philosophy. High thermal mass in walls and floors has been used to
control heat gain. The floors are of reinforced concrete, supported by open steel web
trusses and are placed so that they are offset, allowing for full movement of air
throughout the building space. The blonde brick faced walls have an inner and outer
brick skin, with 10 cm thick insulation between the ventilated brick cavity.
Above: Cross section and longitudinal section through the building (Source: [3])
Natural Ventilation and BMS
The office building has been designed to use natural ventilation whenever possible.
There are two chimney stacks, with high light windows and exhaust fans. When internal
temperatures reach 25C ceiling fans are automatically switched on by the BMS.
Occupants are able to manually override the fans. Once the internal temperature exceeds
29C the BMS switches on a zoned air heat pump A/C system. Different area zones can
be programmed for different temperatures. Night purging is mechanically assisted at 25
air changes per hour. The night purging has been found to reduce the internal air
temperature by 3-4C from the previous day. The night purging and energy use is
recorded by the BMS. During winter, when the internal temperature drops below 19C
the BMS switches on the A/C system for heating. Overall building energy consumption
is monitored by the BMS and during 1996-7 was 90.1 kWh/m2 per year, with 36.7
kWh/m2 for heating, 4.7 kWh/m2 for cooling, 3.1 kWh/m2 for lighting, 3.0 kWh/m2 for
night ventilation, 1.3 kWh/m2 for day ventilation, 24.7 kWh/m2 for computers, the
remaining 16.2 kWh/m2 is for miscellaneous uses such as lifts, faxes and printers 3.
Lighting
The width of the building was limited to 8m to allow for good light entry. Daylighting
studies were undertaken for Meletitiki’s building to determine optimal window size and
placement for good natural daylight. All of the windows are double glazed and are
manually opening, hinged both at the base and side. The windows were limited in size to
allow for adequate natural light, but to prevent a large amount of heat entering and
leaving the building. Internal blinds and individual task lighting is used by each employee
at their workstation to control the level of lighting. External roller fabric blinds,
automatically controlled by the BMS with manual over-ride, are used to control the
amount of heat entering the building.
iGuzzini Luminazione Building, Recanati, Italy
Constructed in 1997-8 the iGuzzini building was designed by Mario Cucinella Architects
(MCA), with environmental input by Ove Arup and Partners. The four storey office
building is constructed around a central atrium and is connected to an existing building
constructed in the 1970’s of high thermal mass. The north and south elevations maximise
the entrance of daylight through a double glazed façade (low emissivity glass, clear float
glass unventilated cavity and clear float glass) with openable low and high level hinged
louvre windows. Solar heat and daylight entering the southern glass façade is controlled
by an external awning with fixed aluminium louvres. The east and west elevations have a
double blockwall skin with insulated cavity.
Ventilation, Heating and Cooling
The building was initially designed to have a fully automatically controlled ventilation
system, allowing for natural ventilation 55 per cent of the time. When natural ventilation
is not in operation, heating and cooling is mechanically managed by fan coil units. The
system operates in two modes, daytime and night time. Initially the BMS was
automatically set but following post occupancy surveys each floor has been separated
into zones, with each zone being able to be manually controlled. A thermostat at each
work station can be manually set by the occupants to change the preference for
mechanical or natural ventilation within the comfort zone of 20-23C  3C. An
occupant survey found that the occupants were happier to have more control over
changing their environment. During night time cooling the BMS automatically opens the
higher level louvres 25 cm and exhausts the air to the 12 vents at the top of the atrium.
Internal Lighting
The BMS uses sensors to monitor the light level within the offices and to ensure that
there is sufficient natural daylighting. When there is too little natural light the BMS
automatically switches on artificial fluorescent lights.
Central Atrium
The central atrium is used to provide good daylight and stack ventilation. There are 12
skylights over the atrium with vents that can be opened or closed to control air flow
through the building. The vent openable area is half that of the total openable office
window area. When the building is operating in natural ventilation mode the warmer air
rises through the atrium and is exhausted through the skylight vents.
Monitoring of Building Performance
During 2000-2001 monitoring of the building was undertaken by the University of
Ancona. The internal and external air velocity, internal and external temperature, solar
radiation and humidity were all monitored6. It was found that mechanical cooling and
heating were predominant in summer and winter, with natural ventilation predominantly
used in autumn and spring. It was found that there was little temperature variation over
the building height (less than 2C) resulting in little stack ventilation6. Smoke studies
showed that the internal air flow is predominantly horizontal, with very little vertical
stack air flow. Monitoring of the building since construction has highlighted the
difficulty in optimally designing for efficient daylight and ventilation. Occupant use,
preference and complex building geometry and material use all contribute to the success
of the energy efficiency strategies adopted.
Department of Physics, University of Athens
The Department of Physics at the University of Athens has extensive involvement in the
design of bioclimatic buildings, in design, research and education.
The Department has specifically built five laboratories for research and experimental
work.
 Laboratory One has two specific equipment pieces used to measure the reflection,
absorption and transmission of light and solar heat through different materials such
as glass and paints. A database of different materials is being developed for designers
to have access to a list that they can use for comparison in specification.
 Laboratory Two has been specifically built with openable double glazed windows and
external rotatable metal louvres. Sensors have been placed within the lab to measure
the internal room temperature, solar radiation entering and the wind flow through
the lab.
 Laboratory Three has a GCMS machine to measure the air quality of a sample taken
from within a building or other area. The GCMS measures VOC, CO2 and other
specific trace gas levels within the sample
 Laboratory Four was initially set up to measure the solar radiance entering through a
double glazed window. Sensors had been placed through the room to determine the
diffusion of light throughout the room. The lab is now being transformed for the
measurement of air ventilation measurements in a building.
 Laboratory Five has an artificial sky and heliodon to model the movement of the sun
throughout the sky. Sensors, linked to a computer, are placed within a 1:20 scale
model to determine daylight distribution levels within the building at various times.
The Department of Physics has links to the following research bodies:
 Air Infiltration and Ventilation Centre (AVIC) promotes the design of energy
efficient ventilation through publications, newsletters and conferences.
 SAVE 13 program to develop training modules on energy efficient building design
for building professionals and technicians.
 European Renewable Energy Centres Agency (EUREC Agency) an umbrella agency
representing scientists from European scientists to encourage cooperation between
research and development, public authorities, industry and the public through
training, research and information projects.
 Advances in Building Energy Research (ABER) an annual journal of reviews and
analyses of energy efficiency and environmental performance of buildings.
 Sustainable Housing in Europe (SHE) a demonstration project of sustainable
housing in Europe and development of qualitative guidelines for good design.
 MUSEUMS under the European Commission Directorate General Energy and
Transport an evaluation of museum projects to demonstrate that energy efficient
buildings can meet thermal comfort criteria.
 OFFICE under the European Commission Directorate General XII for Science,
Research and Development to develop a handbook for the theoretical and practical
application of retrofitting office buildings for energy efficiency.
 International Energy Agency Annex 35 Hyvent a research project 1998-2002 for the
review of existing buildings using hybrid ventilation and development of design tools
for hybrid ventilation.
Conclusion
The study tour has shown that it is possible to design a bioclimatic building that is more
energy efficient than a building that is designed with conventional mechanical lighting
and heating/cooling systems. Bioclimatic design needs to be incorporated into the
design at concept stage and be part of the overall design philosophy. When designing it
is important to consider natural lighting in conjunction with natural ventilation,
landscaping and air flow. To simply consider natural ventilation without considering
solar heat gain and daylighting is not sufficient. Provision of external shading to glass
may be required to control solar heat gains.
Bioclimatic design is complex, due to building geometry, orientation and individual site
features. There are a number of simple and complex mathematical and laboratory
modelling techniques that are available for use, but these may need to be validated
against full scale site prototypes to check design performance.
Education of the building occupants of the bioclimatic design system is paramount to the
success of the building operation. The more people are able to control their own
personal space the more likely they are to be happy with the building. The preferred
building solution for energy efficiency and occupant satisfaction is to incorporate a BMS
that has automatically controlled ‘zoned areas’ with workstation manual over-ride.
Comprehensive monitoring is needed by a BMS once the building is in operation.
Buildings often behave in a way that was not well understood in the design process.
Despite the higher initial cost of a bioclimatic building, monitoring has shown that
thermal comfort and reduced energy consumption can be successfully achieved.
References
1 EMET Consultants Pty Ltd & the Solarch Group 1999, Australian Commercial Building
Sector Greenhouse Gas Emissions 1990-2010 Executive Summary Report 1999, The
Australian Greenhouse Office, December 1999.
<http://www.greenhouse.gov.au/energyefficiency/building>
2 Meletitiki-A.N. Tombazis and Associates Ltd & Department of Applied Physics
University of Athens 2004, Museums – Energy efficiency and sustainability in retrofitted and
new museum buildings - Archaeological Museum of Delphi, Greece, European Commission
Directorate-General Energy and Transport, December 2004.
3 Meletitiki–Alexandros N. Tombazis and Associates Architects Ltd, ‘Office Building
Complex Offices for A.N. Tombazis and Associates Architects Polydroso, Athens’.
4 Meletitiki-Alexandros N. Tombazis and Associates Ltd, The Martin Centre for
Architectural and Urban Studies, University of Cambridge and Protechna Ltd,
Papageorgiou Foundation General Teaching Hospital Thessaloniki Greece, European Commission
Directorate General XII for Science Research and Development Contract JOU2-CT920024 September 1995
5 Meletitiki-A.N. Tombazis and Associates Ltd, Retrofitting of Museums for Antiquities in the
Mediterranean Countries Case Study: The Archaeological Museum of Delphi, European
Commission Directorate General XII for Science, Research and Development Joule
III Programme Contract JOR3-CT95-00013, September 1998.
6 Principi, P, Di Perna, C & Ruffini, E 2002, Pilot Study Report: iGuzzini Illuminazione,
Racanti (Macerata) Italy, International Energy Agency - Energy Conservation in
Buildings and Community Systems Annex 35 Hybvent, February 2002.