Cooling without air conditioners:

Study on alternatives

Noé21 Geneva, june 2012

Interior comfort depends on the control of temperature. Active cooling using refrigerant-based devices can be replaced by passive cooling methods using surrounding natural resources. Savings are not only obtained by avoiding refrigerant gases (these gases are 1000 to 10,000 times more harmful to the climate than CO2), but also by reducing energy demand.This study explains known hybrid technologies, mechanically powered, using natural resources. The different natural cooling systems presented in this study are all existing and have been used for years although often overshadowed by the arrival of air conditioners.

PURPOSE

TABLE OF CONTENTS

p.1 PURPOSE

p.2 SITUATION - TECHNICAL POSSIBILITIES

p.3 GEOTHERMAL WELL

p.4 SOLAR CHIMNEY

p.5 DOUBLE SKIN FACADE - ACTIVE FACADE

p.6 ADIABATIC EXCHANGER

p.7 THERMAL MASS - GREEN ROOF

p.8 GREEN WALL

p.9 BIOCLIMATIC ARCHITECTURE - SINGLE AND DOUBLE MECANIC VENTILATION

p.10 WMO - WORLD METEOROLOGICAL ORGANIzATION

p.11 BRE - BUILDING RESEARCH ESTABLISHMENT

p.12 OFS TOWER - FEDERAL STATISTICAL OFFICE

p.13 SCHOOL «TANGA»

p.14 CODHA - RESIDENTIAL BUILDING

p.15 ELITHIS TOWER - DIJON

1

Current technologies are mature enough to control indoor temperatures according to a standard demand while keeping a good ratio of energy consumption. Switzerland for example sets the average interior tempe-rature of comfort at approximately 21°C.If this temperature was the average standard everywhere, it is understandable that in countries with much warmer climate like South-east Asia, the work on the building, installation and technical energy consumption (total embodied energy) would be much more complicated.In most tropical climate countries, buildings are equipped with air conditioners. Construction standards are relatively poor and non-insulated, leading to large energy losses. External heat enters buildings too easily and in return, cold air provided by the cooling device seeps out too easily.We see these situations in rich countries too (USA, Japan, South Korea, etc ...).

Reflecting on the relation between building and local climate is too rarely taken into account. And when it is, research on the characteristics of materials available to improve the thermal insulation of the building is too often overlooked as the contractor and the architect quickly focus toward decisions of devices that allow full control of indoor climate whatever the external situation.

SiTUATiON

lifecycle

waste

landscape lake,river

plants,animals

water

cloudwindsun

ENERGY

air

Several techniques are available and applicable in new construction and renovation. The approach can be done on several levels.Class A - AirflowThe first source of heat perception within an indoor space is related to the stagnation of ambient air.One of the earliest forms of natural ventilation is simply opening the windows to renew the volume of air in the room. The first category presented in this report includes techniques providing natural air without mechanical aid.Category B - ExchangeThis other category, related to the outdoor climate, works on the thermodynamic properties of the buil-ding. The heat exchange that occurs between the exterior and the interior leading to fresh air for inside ventilation but also supplying warmth for cold months.Category C - ProtectionIn extension to this chapter, another approach suggesting taking the problem from an other angle by considering that it’s not bringing in cold air that cools a house, but preventing hot air from entering. Here we see various proven techniques and material properties in addition to the standard construction rules .Category D - ControlFinally, we will overview current technologies in controlled ventilation devices, electrically fed, which offer great advantages in heavy demand of air renewal.

Realization 11. WMO, Geneva - Switzerland 12. BRE, Watford - England 13. OFS Tower, Neuchâtel - Switzerland 14. «Tanga» School, Falkenberg - Sweden 15. CODHA, Geneva - Switzerland 16. Elithis, Dijon - France

List of techniques studied hereafter:CATEGORY A - AIR FLOW 1. Geothermal well 2. Solar chimneyCATEGORY B - EXCHANGE 3. Double skin facade 4. Active Wall / Trombe Wall 5. Adiabatic coolingCATEGORIE C - PROTECTION 6. Thermal mass 7. Green roof 8. Green Wall 9. Bioclimatic architectureCATEGORY D - CONTROL 10. Single and double mechanical ventilation

TECHNOLOGiCAL POSSiBiLiTiES

2

1. Geothermal wellNatural air conditioning system based on the simple fact that the soil temperature at 1.60 m depthis higher than room temperature in winter and lower in the summer.The well takes advantage of the capacity of the ground to resist changes of air temperature (Thermal mass).The outside air is sent in the building passing through a tube of a certain length buried at least 1.5 meters into the ground. The air enters one extremity of the tube coming out of the ground a few meters away from the building. The soil type also influences the performance of air cooling (see table).

This system is often mixed with mechanical ventilation for maximum efficiency and good air renewal. A house constantly ventilated by this system sees its inner temperature considerably reduced compared to the same house that ventilates 0.5 volume / hour day not using buried tubes. 2

1. http://fr.ekopedia.org/Puits_canadien 2. http://www.fiabitat.com/puits-canadien.php

Several materials are available for tubes used to deliver air flow in the building. The choice must go toward a material offering rigidity to compression (by the earth), being moisture-proof and well insulated from bacteria and radon.Radon is a radioactive gas that occurs naturally in soils, if it passes through the pipes and is distributed throughout the house, it can be very harmful and can cause lung cancer.The amount of Radon contained in soils can differ greatly from one region to another. Maps of Radon risks are established in many countries. 2

Inside the building, the air passes through a fan with a recovery system for eventual humidity createdby the change of temperature of the air between the outside and the inside. 2

Distribution of fresh air inside the building is provided by PE tubes (different than those for air extraction) integrated in the walls or slabs. Air distribution fans are usually located on top parts of walls or slab. 2

CATEGORY A - AiR FLOW

Air IntakeAir intake about 1.00 m in height attached to a concrete slab

Air Intake

Fan

used air

condensate

2%

natural ground

Tube buried undergroundBuried at least 150cm in the ground and very well insula-ted and angled about 2%. The length ofburied tubes is determined by the desired amount of air re-newal. On average, you need 50m of tube with 200mm in diameter to have an interesting impact.

Fan + condensateThe fresh air passes through a fan installed in the basement (several systems with pos-sible regulator, probe, or mono Double VMC, etc. ..) with a re-covery condensate.

Delivery pipe + MouthinsufflationAir passes through PE tubes attached or incorporated in the walls and slabs. It is important to correctly seal the tube to pre-vent air leak.Fans are generally placed at the top of walls in each room of a building (except damp rooms : kitchens and shower rooms)

Principles of operation

1.2

m

3

2. Solar chimneyThe solar chimney is a natural ventilation system composed of a vertical duct, often painted black, exposed to sunlight. During the day, the sun heats the duct creating a suction effect drawing air up the chimney (convec-tion) to ventilate and cool the building.The solar chimney is probably one of the oldest ventilation devices. Other names can be attributed like «wind tower» or «badgir», which is a traditional Persian architecture element. 1

This same type of architectural element exists in many other countries in the Middle and Near East.

Different types of chimneys exist, but their composition remains the same. A surface to capture the heat lo-cated at the top of the chimney is crucial to ensure good solar gain, insulation and thermal properties of the chimney are also crucial; The position, height and the section of the chimney will be crucial, as will the design of the inlet and exhaust vents to adjust the desired ventilation rate.

To optimize the effect of cooling, it is possible to mix a solar chimney system with a Geothermal Well to supply with fresh air without additional mechanical ventilation. Another device for improving the whole system would be to integrate it in a wall with high thermal mass built behind a glass panel exposed to the sun (Trombe wall). The heat absorption is greatly increased through the glass creating a greater suction effect while heating the wall at the rear which accumulates heat that can be returned at night to heat indoor spaces in cold winter nights.Another variation of the solar chimney is the Solar Attic. Often, these attics are overheated in summer due to their exposure to direct sunlight. With the installation of a solar chimney, the ubiquitous hot air can improve the chimney convection, as well as the performance of the ventilation. 2

In Japan, a prototype of solar chimney mixed with a Phase Change Material revealed several difficulties. The device operates like any ‘natural’ device, it must comply with external constraints. For example, the chimney can not function as a natural ventilation overnight or during a very clouded day. In some cases, the solar chimney is considered an unstable system.3

Principle of operation of a wind tower - Badgir

Principle of operation mixedwith a geothermal well

picture of prototype of solar chimneymixed with a Phase Change Material

1. http://fr.wikipedia.org/wiki/Badgir 2. http://fr.wikipedia.org/wiki/Cheminée_solaire 3. http://intraweb.stockton.edu/eyos/energy_studies/content/docs/FINAL_PAPERS/4B-7.pdf

4

In the category of devices using thermodynamic principles, we find the large chapter of «double skin fa-cades.» It applies in several areas other than where natural ventilation is used. A double façade can be built to reduce heat losses, to create a sound insulation and even to create a greenhouse effect to heat interior parts.The double skin facade works as a protection envelope for the building against weather constraints that can lead to overheating in summer, cold in winter, etc. ...Here, we shall speak only of «natural» ventilation possibilities in this system, very similar to principles explai-ned above. 1

3. Double skin facade:The double skin facades also called «double ventilated facade» consist gene-rally of two glass facades separated by a cavity of a few centimetres to several meters in some cases.The natural ventilation effect created by the double skin is obtained by the air circulation within the wall, thanks to the phenomenon of thermal draft.The greenhouse effect in the front creates a temperature difference between the outside and the cavity or between the building and the cavity. It is possible to create this movement artificially through air extractors if the natural ventilation is not sufficient.The air circulation within the cavity will determine the ventilation and thermal behaviour of the double skin facade and therefore its influence on the building.As can be seen in the diagram below, the interior and exterior air curtains res-pectively allow to warm indoor air in winter and regulating the temperature in the cavity in summer to avoid overheating. 1

4. Active facade:The Active wall is a facade composed of a high-emis-sivity glass wall in front of a wall with strong thermal mass. Solar radiations heat an air space between the glass and the wall then the heat is redistributed inside with a certain phase shift. For example, with a 40cm concrete wall, the phase shift will be 11 hours allowing a passive heat gain deferred in time.The Trombe Wall is based on the same physical phe-nomenon as the Active Wall but incorporated with openings located at the top and bottom of the wall enabling air circulation to avoid overheating in sum-mer. A vent placed at the top of the glass in open position allows air produced in the heated cavity to escape.Moreover, the greenhouse or bioclimatic conserva-tory is identical to the Trombe Wall’s though consi-dering the air gap as a living space.

CATEGORY B - EXCHANGE

inner air wall

int. int. int. int.ext. ext. ext. ext.

exterior air wall used air evacuation fresh air feed

detail of a glassdouble skin facade

1. http://fr.ekopedia.org/Façade_double_peau

5

trombe wall principle diagram

solar ray

inner vent closed during the nightto avoid inner thermocirculation

thermal radiation

cold air

hot air

doulbe glass

brick wall painted black

5. Adiabatic exchanger :Adiabatic cooling is an air cooling method based on the evaporation of water.Also referred as air cooling by evaporation or natural air conditioning. The process is simple: hot dry air passes through a moisturized exchanger then cools down naturally.The energy required for the evaporation of water is removed from the air, which consequently cools down. The system gains in efficiency with elevated outdoor temperatures. Beyond 30°C, air can cool down more than 10°C which results in a very effective cooling performance.With this system, a pump feeds filters with water. A fan draws warm air from the outside through the wet fil-ters. The air is then cooled down by evaporation.This system works properly if the buildings is well ventilated in order to rapidly remove the moisture generated by it. The device is usually installed outside.A vent system allows to channel air into the needed area before being discharged through natural openings or through extraction systems. This type of cooling is particularly suitable for large volumes and any building where thermal contributions are important.

FIXEDHEAT

you feel36° & 30% H

you feel26° & 70% H

FIXEDHEAT

SENSIBLEHEAT

stif heat situationevaporative

device

comfortable situation

SENSIBLEHEAT

This system has many advantages due to the constant renewal of air that improves the well-being of occu-pants and allows effective removal of fumes and odours. Incoming air is filtered and evaporative air cooling does not dry room air, which A/Cs usually do. In addition, it can be used as «free cooling» during midseason.

This system uses no refrigerant gases, it only requires drinking water to operate and presents low investment costs.Therefore, it is important to have good control of ventilation. Humidity provided in the rooms can cause dis-comfort if it is extracted too slowly.In addition, this system can’t well when the weather outside is hot and humid. The air already loaded with humidity reduce the ability to evaporate water, and thus lower the air temperature.The air temperature brought inside is related to the outside keeping a room at 15°c all year impossible.

1. http://fr.ekopedia.org/Rafraichissement_adiabatique

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water feed

36° & 30% H treated air used airevacuation

LOCAL26°C & 70% H

hygroscopicwall

evaporativedevice

6. Thermal mass:The thermal mass of a material is its ability to store and to redistribute energy whatever the season. It defines the speed at which the building cools down or warms up and allows to avoid unwanted variations from out-side temperature.The heavier the Thermal mass the more it’s possible to protect from the temperature and minimize the effects of heat waves.Phase shifts also appear, which allows to delay the overheat in the summer accumulated during the day.

In hot and humid climates, thermal mass must be rejected totally. It is important in this type of climate to use solutions with very low inertia and with a strong ventilation. There is no reason for a building , store heat during the day to restore it during nights since nights are almost as hot as days.The use of heavy materials with high thermal mass exposed to the sun would create even more uncomfor-table nights. Thus air circulation and renewal appears to be essential to decrease the discomfort resulting from the climate.In constant research to reduce energy waist, «intelligent» materials appeared in the construction market: phase-change materials or PCM.These materials are based on the physical principle that when a body passes from solid to liquid, it absorbs a certain amount of heat and when it passes from liquid to solid state, it gives away heat.

PCMs are usually composed of microcapsules of a special paraffin whose melting point is between 21°C and 26°C.Then, in summer, on hot days the walls containing PCM accumulate heat due to liquefaction of the paraffin contained in the microcapsules, resulting in heat prevented from being transmitted to the room. Avoided temperature shift can reach 5°c without energy use. At night when temperature drops, the fresh air in the microcapsules paraffin solidifies, restoring the accumulated heat . 1

Putting forward the use of Thermal mass means using dense materials such as concrete or thick masonry brick and having the insulation outside the structure. It is important that the inner mass of the wall is not subject to variations of the outside tem-perature.Thermal insulation and thermal inertia are different things.In the first case, it’s the thermos technique; an insu-lating barrier is placed between two different tempe-ratures. This barrier will limit heat exchange.

CATEGORY C - PROTECTiON

1.http://fr.wikipedia.org/wiki/Inertie_thermique 2. http://fr.ekopedia.org/Toit_vert

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7. Green roof:The vegetated (vérifier terme vegetated stp) roof is a concept using earth and plants in replacement for slates and tiles. The construction of green roofs is traditional in many European countries, including Scandinavia. The mixture of earth and rooted plants on roofs generates sound insulation, water, wind and fire resistance using easily available materials. Green roofs are particularly interesting in summer. They reduce the absorp-tion of solar energy thereby maintaining a cooler and more stable indoor temperature.By absorbing heat, green roofs reduce electricity load from cooling devices. Used widely on a city level, they can reduce «urban island heat» effect significantly by reducing the tempera-ture of the city in summer.The temperature inside a building can be reduced to about 2°C. Economically, we can consider that a 1°C of temperature removes about 5% of electricity demand for air conditioning.Furthermore, the roof would have a real influence on the urban microclimate through evapotranspiration and plant respiration (1m2 of foliage evaporate over 0.5 litres of water per day and 1m2 of grass may evaporate to 2.5 litters of water per day).Regarding the selvage membrane, the temperature difference between a conventional roof and a green roof is up to 30°C. In summer, vegetation acts as a natural cooling and avoids sudden alternations of temperature, prolonging the life of the selvage. This type of roof also has the advantage of being more sustainable on the long run. 2

Protected from ultraviolet and solar radiation, waterproofed-material lasts longer. Tar or selvage exposed to the sun can reach a surface temperature of 65°C covered by plants remains at a temperature of 15°C to 20°C.The main disadvantages of this type of roof is the added structure (and investment cost) needed to support the weight of earth and vegetation.1

8. Green Wall:The green wall is a vertical ecosystem conceived as an ecological core. A wall parallel to the protected buil-ding walls.Depending on its orientation and its composition, the wall will be used to protect against winds, weather, noise, light and air pollution.This wall consists of a vertical solid structure, serving as a support, built parallel to the building facade. The structure creates a cushion of air between the building facade and the green wall, well separated to prevent from humidity parts.Water and nutrients are supplied by a network located in the upper part of the structure. The nutritive solution drips along the wall by gravity and seeps by capillary this way the roots take only what they need and are not drowned. Rainwater may be used for this purpose by counting about 200 litres/m2 year.The plants become a thermal insulation, allowing better temperature control for the building especially in sum-mer, since sunlight is reduced. Evapotranspiration of plants contributes to air cooling and humidity control.Maintenance costs can be very important and complicated if the wall area is big. Moreover, maintenance is the same as for any planted surface. Plants should be pruned to contain the most invasive plants, drips should be checked, dead plants should be taken away or buried in pockets of earth in order to maintain the level of organic material, etc.2

Usual detail and compositionof a green roof 3

vegetation

soil

filter cover

draining cover

base sheet

selvage

insulation

humidiry cover

concrete slab

garden roof

light garden roof green roof

1. http://fr.wikipedia.org/wiki/Toiture_vegetale 2. http://fr.ekopedia.org/Façade_double_peau

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Standard detail for green wall

fresh air from outside

green walldouble facade

FANLIGHT SCREEN

1. http://fr.wikipedia.org/wiki/Architecture_bioclimatique 2. http://fr.wikipedia.org/wiki/Ventilation_mécanique_controlée

9. Bioclimatic architecture:Bioclimatic architectures aims at making the best of the natural conditions of a given location and its en-vironment to supply a natural comfort using a mini-mum of additional energy.This approach is not an invention of 20th century, but a traditional architecture, almost forgotten with the arrival of machines allowing to ignore climate and environmental constraints. An example presented earlier is the solar chimney developed in the Middle East.Bioclimatic architecture is a logical architecture that has been revisited by the current trend of green buil-ding constructions.1

Protect

Disperse

Minimize

9

This last chapter presents the possibilities for using less electricity to reduce inside temperatures. This type of installation is currently the most common and can present a very good indoor air control even in situations requiring high air renewal.

10. Single and double mechanical ventilation:This type of installation covers a range of mechanical devices designed to ensure the renewal of air inside rooms, especially for humid rooms (kitchens, bathrooms).With single-flow ventilation system, currently the most common, the system is depressurized by an air extrac-tor. A fan placed in the attic or roof draws air through ducts placed in wet rooms. The air-flow is unidirectional, from inside to outside and the air volume control renewed per hour is done manually by the users.

The double flow system allows to bring-in fresh air in dry rooms (living room, rooms) while the extraction is done in the same way as single-flow system through wet rooms. During winter months, this system can limit heat loss related to the renewal of air. Cold air from the outside is brought into the house by a duct system. Filtered, fresh air passes through a heat exchanger and recovers about 90% of heat from the used air before being distributed in living rooms.

A heat exchanger or ventilation installed in the roof or in room in the basement is connected to extractions placed in the kitchen, bathrooms, toilets and hydrants inductions placed in bedrooms and the living room. This system cap-tures the calories from the used air to temper fresh air brought in.Mechanical ventilation consumes power there-fore contributing to the emission of greenhouse gases. Hybrid ventilation, combining the advan-tages of both modes of ventilation, natural and mechanical, could reduce energy used in buil-ding.

The system is controlled in response to variations in climatic conditions and automatically switches between natural mode and mechanical assistance. 2

CATEGORY D - CONTROL

used air fresh air

living roombathroomkitchen

WMO - World Meteorological OrganizationIntroduction by Brodbeck SA-Roulet:Headquarters of the World Meteorological Organization located in Geneva. The eight-story office building includes : natural cooling, double skin facades facing south, offices, congress hall, conference rooms, library. The restaurant and terrace located in the attic is protected from wind by the double skin facade. 1

ConceptPresentation by Erte SA:- Instead of artificial power hungry cooling devices, a clever and revolutionary natural ventilation system: dynamic facades, comfort ventilation, geothermal well, natural ventilation at night, etc.. Heating, cooling and humidification are efficiently managed.Ventilation is almost completely integrated into the building structure, cancelling space taken on ceilings and raised flooring to recover the equivalent of a floor.With over 1,200 motorized vents, 10 million m3 of air (in other words, more than 100 times the volume of the building) passes through the entire building every night evacuating 3-4°C of heat accumulated during the day. The building is equipped with the largest geothermal well in Switzerland installed in the thick foundations of the parking to preheat and pre-cool the entire building with a capacity of about 250 to 350 kW. Fire escapes also contribute to cooling the building’s temperature management. Three stairways 40m high equipped with motorized dampers become huge natural air chimneys overnight. Air entering from 36 openings located on each floor and escaping from the roof can reach a speed of 50 km/h on the 8th floor.

A joint production of both thermal and electrical energy of 300kW supplies the building from within.In order to maximize natural light, the building is fully glazed. This type of construction required a special en-ergy design based on the «thermos» effect with several outer insulating layers (double-skin or double facade).To reduce infiltration of the cold winter wind well-known in Geneva, a closed window above the north side forms a shield. To protect against the summer heat without using air conditioning, the south facade is com-posed of mobile sunscreens. In winter, they close and cover the building creating a cloak for protection, both north and south. In summer, they are opened. 2

REALiZATiON

1. http://www.brodbeck-roulet.com/realisation.php?pid=SigedelOMMWMO11 2. http://www.erte.ch/fr/refs/refs_omm.htm

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BRE - Building Research EstablishmentArchitects: Feilden Clegg ArchitectsSpecial technical engineers: Max Fordham and Partners

Located in Watford, north of London and built in 1997, the building is rectangular, oriented north-south, with a surface of approximately 2000 m² on three levels for approximately 100 people. The building is divided into two parts around a glazed entrance hall. The largest part has individual offices and open space offices from north to south. The western part, shorter, brings together the meeting rooms and bathrooms. A seminar room is on the ground floor.

ConceptVentilation is completely natural and works with three components; the ceilings of the first two levels have a particular shape, small upper windows controlled by computer and ventilation chimneys on the south facade. Warm air entering the chimney, heated by internal recycling, rises naturally to be evacuated above the chim-neys.The movement of air at the top end of the chimney also promotes the necessary draw.The outer walls of chimneys facing south are made of glass blocks to increase air temperature in the solar chimneys, thus improving circulation. As observed on site the solar gain is not immediate. Glass blocks and other walls of the chimney with their thermal mass supplies warm air during evenings, which is very useful for night ventilation.The fans (80 W each) are used at the top of the chimneys for ventilation when natural ventilation is insufficient (not enough pressure difference between the two facades for ventilation; not enough wind or air temperature in the chimney too low for ventilation). However, these fans have never been used.

The comfort criteria design were:- Not more than 25 ° C over 5% of the time- Not more than 28 ° C over 1% of the time.The building has fulfilled those criteria without the use of mechanical cooling.For example, in 1998, the 25°C limit was exceeded du-ring 40 hours (2% of the time). For a typical summer day 1998, there were 23°C in the first two levels and 25°C on the third level for an outside temperature of 27°C.These values are compared with a temperature of 31°C in a former building site as a reference.

Expected consumption was 83 kWh/m² per year, of which 36 kWh / m² for electricity and 47 kWh / m² for heating. Consumption measured is 135 kWh / m² per year (46 kWh / m² electricity / 89 kWh / m² heating).This difference is attributed to the increase of the com-puting equipment from the initial scheme and wasteful behaviour.The technical elements required for natural ventilation have a cost that probably compensates the economy made by avoiding mechanic ventilation equipment. Elements such as chimneys and sinusoidal floors contri-bute, in addition to their technical role, to the architectu-ral form of the building.

Respect of the investment the size of the system is also important (je cpmprend pas cite phrase). On this point, the comparison with an air conditioned building is diffi-cult to make since the building does not include vertical duct for ventilation, and horizontal ducts are limited.

1. http://www.energieplus-lesite.be/energieplus/page_10876.htm?reload#05 2. http://projects.bre.co.uk/envbuild/

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OFS Tower - Federal Statistical OfficeArchitects: Bauart Architectes SAEnergy Engineers: Sorane SA

Sustainable development and limited budget. Based in Neuchâtel, the first building of the Federal Office Statistical Office (OFS) is distinguished by its slen-der geometry that highlights the railways on a narrow strip of land next to the train station.Its architecture and design displays a modern image reflecting the nature of the activities in which the building is dedicated to.Today, a second slender volume 50m high, fifteen levels, completes the construction of this decentralized federal administration in Neuchâtel. The building marks the head of the OFS complex, the first element of the planned development of this area called to be a model urban development including options for more constructions. The program, entirely dedicated to administrative activities is defined around the theme of sustainable deve-lopment. The building addresses many technical constraints to be carried out within a very limited budget.

ConceptThe approach in this project was to reduce the demand for heat at a much lower level than today’s by the systematic use of heat extraction (air transfer into the building using inner spaces as traffic vectors), and the use of a solar system with seasonal heat storage covering part of the remaining need for heat.The other important point is to reduce electricity demand by exploiting passive cooling for the computer centre, and natural ventilation for offices (using the chimney effect) and by taking maximum advantage of natural light.

The following measures are the main elements for reducing the demand for cool air: Natural ventila-tion eliminates the need for technical devices for office ventilation North and South (see figure be-low). Cooling of the computer centre is provided mostly by a heat exchange with outside air.The reduction in cooling requirements reduces use of pumps, reduces breakdowns and simplifies fa-cilities in general, all resulting in reduced electricity consumption.The initial demand for heat is reduced mainly by enhancing the release of used air from blind (blind ?? synonym stp, je voyaos pas ce que tu voulais dire, chambre borgnes ? sans fenetres ?) rooms and the recovery of heat from rooms equipped with machines (computers, photocopiers, etc).

This development is carried out by a central system managing the displacement of warm air using the Buil-ding’s corridors for circulation instead of a duct network. The demand for heat is covered in part by the solar installation. The rest is covered by a gas heater.

1. http://www.sorane.ch/ref_OFS.htm 2. http://www.architectes.ch/files/file_id=821

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SCHOOL «TANGA»Architects: CNA - Christer Nordström Architects in cooperation with EfemEnergy engineers: Ake Blomsterberg, WSP - SP Swedish Testing Institute

The school, located in a suburban area, consists of 4 buildings on 2 levels, for a total area of 9’350 m2 The building was built in 1968. Partly renovated in 1989 (new windows) and 1991 (improving thermal insula-tion).A new renovation took place in 2000. The B-wing, an area of 3’672 m2, equipped with a double-flow ventila-tion system, was replaced during the last renovation with a hybrid ventilation system: natural ventilation with solar chimney with an assistance fan when necessary.The payback period calculated on the total investment is around 17 years. But this calculation ignores the fact that a renewal was necessary anyway because of outdated equipment.

Classes are ventilated with air introduced by grids on facade (3 or 4 per class). During winter months incoming air is preheated in pipes above the hea-ters before being released in the room.The front grids are drawn and equipped to prevent the intrusion of rain, snow, insects, etc. They can be easily cleaned manually. The occupants can also open some windows. This ventilation with unfilte-red outside air is possible thanks to the suburban environment of the school, without significant noise or pollution.

The inflow and outflow of air in each class is ma-naged automatically by a CO probe. Valves begin to open when the concentration exceeds 1000 ppm of CO2 and are fully open beyond 1500 ppm.The teacher always has the option to switch to the automatic mode or manually close in the range 50 to 100%. To assist in this manual assistance a red lamp lights up in class if the CO level exceeds 1000 ppm.Extraction through the chimneys is also automa-tically controlled depending on the temperature difference between the base of the chimneystack and the outside. If the difference is insufficient, the fan automatically starts and the bypass register is closed.The price of investment and energy savings carried out by the heating system through hybrid venti-lation is similar to those resulting from the use of traditional double-flow ventilation system with heat recovery and simple time management. However, this system saves a consequent amount of elec-tricity.

Air is drawn naturally by of 6 meters high solar chimneys : glazing at the foot of the chimney heats the air extract which enhances the suction effect. When the external conditions are not favourable and the naturally extracted air flow is insufficient, a fan with variable frequency compensates the lack of ventilation.

1. http://www.energieplus-lesite.be/energieplus/page_10874.htm?reload 2.http://www.new-learn.info/packages/euleb/fr/p10/index_s1.html

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CODHA - RESIDENTIAL BUILDINGArchitects: Ganz & MullerEnergy engineers: Dominique Hirt

The two buildings complete the «Pommier» district, where almost 20 buildings were built in ten years.Located in the Grand Saconnex area, between Geneva Airport and the international organizations area the building is built according to Minergie plus and Eco standards.Minergie Eco requires the use of natural materials and lists relative and absolute rules. All adhesives, all that contains formaldehyde is forbidden, as are foams used by carpenters.

At first look, the elements look similar to wooden venetian blinds put under glass. Solar glass lets in almost the total of solar energy within the device. The wood lamellaes, by their inclination, bring the heat produced by the light energy to the composition of the facade.The inclination of the lamellaes is calculated to have the best results, both in winter and summer. Lucido ®, the operating principle concept is similar to the Trombe wall.1

Sunlight reaches the absorbing plates, the facade stores the energy and transmits a part of the heat inside the house. The facade also fulfils an insulating role. In summer, when the sun is high, the sun’s rays are reflected by the structure of the solar glass. Because of the inclination of the lamellaes, the bulk of the absorber is shaded, so only the parts of the lamellaes are in contact with the light.The heat from the air layer is removed by convected heat. This process prevents the system from overheating. A conventional wall made of wood or concrete, existing or newly constructed, performs the structural function of the facade as the wooden lamellaes are fixed on it. A solar glass is installed on aluminium, wood or metal frames, these supports separates the glass from the wood and thus constitute an air gap.2

1. http://www.habitation.ch/images/sommaire1-2.11.pdf 2. http://www.lucido-solar.com/

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ELITHIS TOWER - DIJONArchitects: Jean-Marie Charpentier - Office Arte-Charpentier ParisEnergy engineers: Elithis

Finished in 2009, the building is the first positive energy (producing more energy than consumes) office buil-ding in the world built with standard costs. It is recognized as one of the most efficient buildings in the world.The Tower is an emblem of «new generation» of tertiary buildings.In detail, the estimated consumption of the building was 70 kWh/m²/year. Designers hope to reduce the consumption by 20 kWh/m²/year to a minimum through what they call «ecomanagement «, working with the employee awareness and empowering them to reduce consumption using power strips to cut all power com-puting devices, encouraging employees to use stairs instead of the elevator, and adapting lighting according to natural light. The remaining 50 kWh/m²/year will be generated by 342 photovoltaic solar panels integrated on the roof, that is 560 m2 of panels with an annual production expected to reach 82,000 kWh.

Building a «solar shield» was necessary to limit overheating problems and air conditioning in this 75% glass facade building. It is partially covered with a flat metal sheet. The angle created by the metal sheet allows part of the heat to be trapped inside in winter and mid-season while in summer it protects from direct solar radiation, but lets the light enter.For fresh air and to cool down the building where the windows cannot be opened, a trademarked triple flow ventilation system has also been integrated. The engineers developed a ventilation system to renew the air of the building while recovering the heat from the used air as in the usual double-flow ventilation.Integrated system components opens the exterior opaque allowing the intake of outside air to cool the interior temperature.More innovative, when the triple flow is insufficient, the adiabatic cooling takes place.Once cooled, used air is fed to a heat exchanger, thereby cooling the incoming air through a heat exchanger. Another technology trick to reduce the building’s energy consumption, a heat transfer group recovers energy generated by servers and sends the heat into the building thereby reducing heating requirements. Heating needs will thus be provided, completed by two wood pellet boilers requiring between 8 and 10m3 of wood per year.

1. http://www.elithis.fr/2012/01/30/tour-elithis/ 2. http://www.ddmagazine.com/1131-tour-a-energie-positive-Elithis-Dijon.html 3. http://fr.lombard.free.fr/

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Accredited to the UNFCCC, UN Framework Convention on Climate ChangeNoé21 - 19 Quai Ch. Page - 1205 Geneva - Switzerland - Tel. +41 22 329 51 36 info@noe21.org

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Tel : +41 22 329 51 36 - www.noe21.org - info@noe21.org

Noe21 is the french acronym for New Economic Orientation for the 21st CenturyIndependent NGO specialized in solutions to climate change

Member of the European Environmental Bureau and Climate Action Network-EuropeMember of Alliance pour le climat (Suisse)

Accredited to the UNFCCC, UN Framework Convention on Climate Change

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