windows_low_energy

E N E R G Y

C O M F O R T 2 0 0 0 European Commission Thermie Project to reduce energy and improve comfort and environment

What is EC2000?

A Thermie Target Demonstration Project including 7 new nondomestic buildings;

> with linking activities between sites; > demonstrating the latest low energy techniques;

Windows – the Key to Low Energy Design

> covering design, construction and monitoring;

> promoting the concepts and stimulating replication.

I N F O R M AT I O N D O S S I E R

NUMBER

5

MARCH 1998

The EC2000 principles

> reducing energy consumption by 50% compared with traditional Contents buildings;

Introduction

> reducing Principles CO2 emissions used by in EC2000 up to 70%;

Case studies

> avoiding air-conditioning, or tools Design minimising its energy use; Conclusions

> providing good internalReferences visual and thermal conditions;

> allowing individual control of lighting, heating and cooling where possible;

> stimulating environmentally friendly design and construction.

Building uses Offices; Lecture rooms; Learning Resources Centre; Municipal facilities; Sports arena; Exhibition and conference facilities.

This information bulletin is one of a series reporting on the experience of the design, construction and monitoring of EC 2000 buildings

1

Fire Safety in Atria

2

Natural ventilation and cooling strategies in new office designs

3

Energy efficient buildings – the Client’s view

4

Control strategies for passive buildings

6

Design standards for energy efficient buildings

7

Environmental assessment of seven new buildings

8

Energy efficient building technologies explained

Energy Comfort 2000 Information Dossier

Windows - the Key to Low Energy Design

This information dossier is one of a series reporting on the experiences gained during the design, construction and monitoring of EC2000 buildings. The dossiers have also been enhanced by the inclusion of experiences and case studies from other buildings outside the EC2000 project.

Authors: Esbensen Consulting Engineers

Energy Comfort 2000 Information Dossier

Windows - The Key to Low Energy Design Introduction The use of windows in building design has changed through history. For many centuries windows were primarily considered only as a way of letting daylight into buildings, thus daylight was the dominant interior illuminant during daytime.

This changed as a result of the oil embargo in 1973 when there were believed to be significant benefits in designing deep plan commercial and institutional buildings with small unopenable window apertures.

These kind of buildings were only inhabitable when equipped with large mechanical ventilation and cooling systems and usually the artificial lighting would be on throughout the day. The philosophy of these sealed buildings was that the main function of the building envelope was to act as a climate protector. The result was that occupants were deprived of sunlight, daylight and contact with the outside world. Many buildings with sick building syndrome have the above characteristics.

In the low energy bio-climatic buildings of the 1990's, design is focussed again on the window and its associated components. The building envelope is now seen as a climate modifier, mediating the effects of daylight, solar gains and wind into the energy system of the building.

In this dossier, different design techniques and associated problems related to sidelight windows will be briefly described. Finally the actual sidelight window design in five EC2000 building projects and one building not related to EC2000 will be presented.

General description of sidelight window design The function of the window Basically a window consists of a window frame and a window pane (usually called the glazing).

Windows are multi-functional elements which have to: • Provide sufficient daylight into the building, (without causing glare).

• Keep out excessive solar heat.

• Allow visual contact with the surroundings 2

• • • • •

(preferably uncoloured).

Keep out excessive noise.

Ensure good weather protection.

Provide good insulation.

Ensure safety.

Allow controllable ventilation air into the building.

A successful window design needs to find the optimum balance between these demands. This can be difficult because many of the demands are directly in contravention with each other. For example: • A large window area will in general be of benefit in terms of daylight penetration and passive solar, but a problem in terms of heat loss, solar overheating and glare.

• A high insulation value of the glazing will reduce the heat loss in winter, but can increase overheating in summer (depending on the outdoor temperature).

• Non clear glazing keeps out daylight and solar gain thus reducing overheating. At the same time the artificial lighting has to be on for a longer period during the day thereby increasing overheating.

• Poorly designed glazed areas will cause glare forcing the occupants to use the solar shading.

This can lead to an increase use of artificial lighting and consequent overheating.

Glazing The characteristics of the glazing depends on the type of glass in the pane, the thickness of the glass, the number of glass sheets used, the thickness of the cavity between the glass sheets and the type of gasfilling in the cavity.

Three key values are used to characterise the glazing type: • The transmission coefficient also called the Uvalue, expressing the heat loss per square metre glazing per temperature difference between inside and outside (W/m²K).

• The light transmittance τlight expressing the fraction of visible sunlight transmitted through the glazing (%) at normal incidence.

• The solar heat transmittance τsolar expressing the fraction of solar heat transmitted through the glazing (%) at normal incidence.

EC2000: Windows - the Key to Low Energy Design

Energy Comfort 2000 Information Dossier

Windows - The Key to Low Energy Design Comparative values for some of the main pane types can be found in Figure 1. It should be emphasised that Figure 1 only shows a few of the almost unlimited number of pane combinations on the market today. By combining the type of glazing it is possible to create a pane with a variety of characteristics appropriate for a given situation.

Type of Pane

U-Value W/m2K

τlight %

τsolar %

Clear glass Single glass, 4 mm

6.0

88

83

Double glass with air (4-12-4)

3.0

80

76

Double glass with low E coating & Argon (4-12-4)

1.5

77

65

Triple glass with air (4-12-4-12-4)

2.0

72

67

Triple glass with low E coating & Argon

1.2

70

60

Vacuum pane with low E coating (4-12-4)

0.5

77

65

Double medium reflective glass with low E coating (612-6)

1.6

29

39

Double glass, Bronze + low E coating with Argon (6-12-6)

1.6

9

13

have a much lower U-value than the same type of pane with gas. This is because the convective and conductive heat loss will be almost completely eliminated. Such a pane called a vacuum pane is still under development although prototypes already have been produced.

In addition to the above ‘normal’ window panes there are also a large number of panes with special functions like sound insulating panes, fire protective panes and safety panes.

Sound insulating panes (acoustic panes) are often used in buildings situated in noisy areas e.g. in city centres or near railway tracks. In such situations acoustic panes often represent the only technical, economic and practical solution to reduce uncomfortable noise for the building occupants. The sound insulating quality of a window depends on characteristics of the pane, the frame and the connection between these.

Smart windows

Reflective glass

Figure 1 Example of key values for different pane types [1], [2].

Low energy coating on the glass (low E glass) can be used to re-reflect long wave radiation into the building, thereby decreasing the radiation heat loss and so the total heat loss through the pane. Gases like argon, xenon and krypton can be used instead of air in the pane cavity to decrease the convective heat loss of the pane (because of the high density and low heat capacity of these gases).

Following the above methodology it can be seen that a pane without any air or gas in the cavity, will EC2000: Windows - the Key to Low Energy Design

Another new window pane development which probably will become a design option in the near future is the use of ‘smart windows’. Such a pane can alter its transparency in response to outside or inside conditions, such as temperature or solar gains on the surface. This is accomplished by a variety of methods, including coatings on the glass surface, or the use of a gel polymer between two panes.

Designing a building with ‘smart’ windows will make it possible to take full advantage of the benefits of daylight and passive solar whilst avoiding the negative consequences arising from glare and overheating. Still, it is important to understand that such a design component needs careful consideration, if the potential is to be fully exploited.

Overheating One of the most serious problems related to glazed areas is overheating of the room behind the window.

It is therefore essential to design the window in conjunction with different techniques that can keep overheating within certain limits. Air-conditioning could be used, but it is very energy consuming, has high capital and running costs and is frequently not

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Energy Comfort 2000 Information Dossier

Windows - The Key to Low Energy Design particularly favoured by occupants. Passive techniques include applying effective solar shading to the windows (see below), use of exposed thermal mass to absorb heat, ventilation of the building during the night to cool down constructions and to some extent, use of reflective glazing. The last mentioned should be carefully considered due to the problem with artificial lighting (see above).

Venetian blinds are often used as glare shading intended to be used during heating periods where solar gains are usable.

Some comparative solar shading factors (Fsolar) for different shading systems can be found in Figure 2.

The factor is defined as the relation between the total solar gains passing a window with solar shading (Ishaded) and without solar shading (Iunshaded):

Solar Shading Fsolar = Ishaded/Iunshaded When considering the type of solar shading necessary, it should be noticed that there is a difference between solar shading designed to prevent overheating and glare. During winter glare is often a problem due to low angle sun, but solar gains can still be utilised for reducing heating loads.

It may be optimal to apply more than one solar shading system to a window.

There are two main types of solar shading; fixed and movable shading devices. Fixed devices include overhangs, louvres, fins and a combination of these e.g. egg crate. Most fixed devices are placed outside the glazing.

Examples of movable devices are awnings, Venetian blinds and roller blinds. Awnings are normally placed outside the glazing while the blinds either can be placed outside, inside or between the glazing layers.

Which shading devices are chosen for a given building depends on the geographical position of the building, the climatic environment of the site and the orientation of the window. Movable solar shading devices are in general preferable because they respond better to the dynamic nature of weather than fixed devices, but a fixed device such as an overhang can be an effective supplement to movable solar shadings in Southern climates and on South elevations in general (cutting of high sun angles during summer while still admitting low angle usable solar gains into the building during winter).

Internal solar shading is less effective than an external device in terms of preventing overheating because the solar gains have already passed the glazing and affected the climate in the building.

This is the reason why internal roller blinds or

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The smaller solar shading factor, the more effective the solar shading. Fsolar is usually defined for a normal double pane. The value for Fsolar should therefore be multiplied with a correction factor K if other kinds of panes are used.

K= Ď„solar (actual pane)/ Ď„solar(double pane) If the shading factor should be calculated in terms of daylight then Ď„light should be used.

Type and position of Solar shading

Colour of shading Light

Medium Dark

Internal Venetian blind

0.6

Roller blind (non transparent)

0.3

Curtain (medium transparent)

0.5

0.7

0.8

Venetian blind

0.35

0.45

0.5

Curtain (medium transparent)

0.3

0.4

0.5

0.75

0.85 0.7

Between glass sheets

External Venetian blind

0.1-0.2

Curtain

0.1-0.25

Awning

0.25-0.5

Overhang

0.2-0.8

Figure 2 Typical solar shading factors for different shading systems [2]. Based on a normal double pane.

EC2000: Windows - the Key to Low Energy Design

Energy Comfort 2000 Information Dossier

Windows - The Key to Low Energy Design Daylighting systems Solar shading devices can sometimes be combined with elements intended to increase the daylight level in a building. Figure 3 shows a qualitative light distribution in a room without and with such a system [3].

In general the main advantage of light shelves is that daylight is distributed into the building in a more even way than without the light shelf.

Depending on the angle of the sun an external light shelf can increase the amount of daylight entering a building. An internal light shelf cannot increase the amount of daylight entering the building, only redistribute it.

Artificial lighting and daylight

300 - 500 lx

illuminance

300 - 500 lx

illuminance

Figure 3 Qualitative light distribution in a room without (above) and with (below) a light guiding system. [3] Examples of such systems are: a) Passive systems - Light shelves - Angle selective glazing: lamella, reflective structures, prisms, patterned glass, laser cut panels. b) Tracked systems - holograms - heliostats The most common systems are light shelves and reflective blinds. The intention of both systems is basically to reflect light into the ceiling and into the back of the room.

To protect the reflective surface against smudges, reflective blinds will commonly be situated between the glass sheets.

It is very important to design the artificial lighting system in a way that takes the daylight level in the building into account. This can be done by installing light sensors in the offices and in this way controlling the artificial lighting in response to the daylight level. Also high efficiency lamps and systems controlled after occupancy (presence detectors) and working periods are important elements of reducing overheating and saving energy.

Window shape The recommended shape of the windows in an office building depends equally on the depth of the room, the panoramic view out of the window and the orientation of the window. If an office room is deep, it is necessary to use high windows to ensure an effective daylight penetration into the back of the space. In terms of views, a distant panoramic view calls for a wide window while a near view with a high skyline calls for a high window. Again the preferable solution is a balance between several demands. A solution often chosen is to divide the window into a lower part (the vision window) intended for views and a higher part (the daylight window) intended to allow daylight deep into the building. Another advantage is that the two kinds of windows can be shaded differently in line with their different uses.

Light shelves can either be placed outside the window and thereby at the same time act as an overhang or inside the window thereby shading the perimeter of the building from glare coming from the window above the light shelf (the daylight window, see below).

EC2000: Windows - the Key to Low Energy Design

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Energy Comfort 2000 Information Dossier

Windows - The Key to Low Energy Design Case studies The EC2000 buildings will be monitored after

Introduction To exemplify different window design six building projects are described below. Of these, five are involved in the EC2000 project (case 1-5) while one is not (case 6): Case 1: Case 2: Case 3: Case 4: Case 5: Case 6:

Anglia Polytechnic University Learning Resource Centre, UK. The Leeds City Office Park, UK. The Tax Office in Enschede, Holland.

The AVAX Office Building in Athens, Greece.

Lisbon Expo’98 Multipurpose Pavilion, Portugal.

Bang & Olufsen Headquarters, Denmark.

All the EC2000 buildings are designed with the aim of minimising energy consumption at the same time as providing a comfortable internal environment all year round. The techniques used to obtain this goal are principally the same in the different projects.

This means maximising the use of daylight and passive solar, using high levels of insulation in the structures, using the thermal mass in the building structure for passive cooling and finally utilising stack driven natural ventilation.

completion during a occupancy period as a part of the EC2000 Thermie programme.

Case 1: Anglia Polytechnic University Learning Resource Centre Anglia Polytechnic University Learning Resource Centre (LRC) in Chelmsford UK, combines the functions of library, student study areas and recreational areas under the same roof.

The LRC is rectangular in plan, increasing in elevation at the point where the two centrally located atria occur (see Figure 4). The building is constructed around a North-East, South-West axis with staff offices, canteen and study desks in the perimeter of the building. A T.V. studio and secondary rooms like lavatories and plant room (all mechanical ventilated) are situated in the centre of the building.

The design phase started in March 1993 and the building was completed in September 1994.

The following description corresponds to the sidelight window design in the open plan study desk area.

The atria implemented in case studies 1-3 and the large space in the Expo’98 Pavilion are an essential part of this strategy allowing both daylight and passive solar into the core of the buildings and at the same time creating the buoyancy for the natural ventilation.

The windows are multi functional in all the case study buildings providing daylight, passive solar and ventilation to the building and at the same time ensuring good acoustic and visual contact with the surroundings.

To optimise these potentially conflicting demands, a number of state of the art computer simulation software programs have been utilised in the design process, including software for thermal simulations and daylight simulations.

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Figure 4 Elevation of the APU Learning Resource Centre.

The window design The net room height is 3.0 m in the LRC. This relatively large room height allows for a design with high windows resulting in effective daylight penetration deep into the building. The window area

EC2000: Windows - the Key to Low Energy Design

Energy Comfort 2000 Information Dossier

Windows - The Key to Low Energy Design accounts for approximately 30% of total area of the facade adjacent to the study area (30% glazing ratio). The floor to window height is 1.0m. Figure 5 shows the window design.

situated above the vision window reflecting daylight deep into the adjacent room, while cutting out direct sunlight near the perimeter thereby minimising glare problems. The reason for using two light shelves is that the shaded area is much larger than if only a single light shelf was used.

Additional external solar shading in the form of a fixed overhang has been used on the South-West facade of the building because computer modelling carried out in the design phase predicted overheating problems on this elevation. The overhangs are situated above the vision window like the internal light shelf. In this way it shades the vision window from high sun angles without obstructing the daylight window.

Figure 5 Window design in APU Learning Resource Centre.

The windows are divided into a lower part (the vision window) and a upper part (the daylight window) each with the same width depending on where in the building the respective window is placed. The total height of the window is approximately 2.0m with the vision window counting for about 67% of this.

The vision window is a triple glazed window (openable for cleaning) containing a manually controlled integral blind for protection against glare and overheating. The blind is vented to the outside thereby making it more effective in terms of preventing overheating.

The transmission coefficient of the glazing, the U-value, is 1.6 W/m²K and the light and solar transmittance 0.72 and 0.67 respectively.

The daylight window is a triple glazed clerestory window which can be pivoted to allow for summer ventilation. The glazing U-value is 1.95 W/m²K. In the open plan areas the opening and closing of the windows are dictated by room temperature sensors and balanced with the opening of the roof vents in the atria by the BMS. In partitioned offices with single sided ventilation the windows are manually controlled.

Artificial lighting is provided in most areas by compact fluorescent down lighters which are controlled to respond to daylight levels during the day and automatically switched off at the end of the day. Manual override is provided by local wall switches. The study desks have their own task lighting under the direct control of the users.

As a consequence of the low energy design the annual energy consumption for heating, lighting, ventilation and control facilities are calculated to be around 90 kWh/m². It is important to notice that a better figure could have been accomplished if individual control of lighting, heating, window blinds etc. had not been in the design. On the other hand, these local control facilities are an essential part of the strategy of making the building user friendly.

Case 2: The Leeds City Office Park The 6366 m² Leeds City Office Park is a three storey building containing open plan office spaces on all floors and a car park in the basement. The building is situated along a North-South axis, with the main entrance in the South end leading directly to the centrally located atrium (see Figure 6).

The design phase started in the spring of 1993 and the building was completed in September 1995.

All windows have internal twin light shelves EC2000: Windows - the Key to Low Energy Design

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Energy Comfort 2000 Information Dossier

Windows - The Key to Low Energy Design

Figure 7 Window design at Leeds City Office Park.

Figure 6 Leeds City Office Park.

The window design From the beginning of the design phase of the Office Park, it was realised that an essential part of the daylight strategy of the building was to ensure a deep penetration of daylight into the building. As a consequence of this, it was decided to raise the structural soffit of the perimeter thereby allowing the windows to be higher than the normal office floor to window height.

The net height is 2.8 m in the office area increasing to 2.95 m at the window perimeter. The reason for not raising the ceiling height to 2.95 m in general, is that it is very expensive to raise the whole floor instead of only the perimeter.

All windows are divided into a lower vision window and an upper daylight window (see Figure 7). The total height is 2.25 m where the vision window accounts for 67% of this (1.5 m height). The floor to window height is 0.75 m. For each structural bay of 7.5 m there are 5 windows in the facade. Two of these are 1.0 m wide and openable, and three are 1.5 m wide where one is openable. This results in an average glazing ratio of 42%. All glazing facing the outside is clear double glazing with a U-value of 2.8 W/m²K and a light and solar transmittance of 0.72 and 0.67.

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The daylight windows (which are openable) are bottom hung tilting inwards and are manually operated by a pole. The openable vision windows are also bottom hung inward tilting, but can also be fully opened by side hinges through 90° inwards.

This facility is mainly for maintenance and cleaning because the large window swing interferes with the office use and because such an opening will cause draught problems.

Solar shading is provided by combined sun screens and maintenance walkways, positioned horizontally between the vision and daylight windows on each of the three storeys. The screens are intended to cut off high angle solar gains on East, West and South elevations, to provide a limited effect of a light shelf and finally to act as maintenance walkways all around the building. The sun screens extend 1.2 m from the external cladding. Provision has been made in the window design for additional manually operated internal blinds to be fitted to both the vision and daylight windows, if required by tenants.

Artificial lighting is provided by compact high efficiency fluorescent down lighters, the outer zones controlled by daylight sensors and all zones controlled by presence detectors. The users can manually override the automatic system using local hand held controllers.

Due in part to the low energy design methods utilised in the Leeds City Office Park the building achieved a rating of ‘excellent’ under the 1/93 BREEAM environmental assessment scheme. The total annual energy consumption for heating,

EC2000: Windows - the Key to Low Energy Design

Energy Comfort 2000 Information Dossier

Windows - The Key to Low Energy Design lighting, ventilation and control facilities is calculated to be 72 kWh/m².

3.6 m wide, 5.1 m deep and has a net height of 3.0 m high. A strip of sound insulating acoustic ceiling is suspended in the middle of the office room.

Figure 9 shows the window design.

Case 3: The Tax Office in Enschede The EC2000 project in Enschede created a new wing to an existing tax office building. The gross area of the new wing is 4300 m² divided between five floors and a half-open basement. The wing is orientated along an east west axis with the main facades facing south and north. The atrium, which runs almost through the whole building, is also orientated east west, thus dividing the building into two sections.

The South facing part of the building contains offices in the perimeter, a corridor in the middle and toilets, computer rooms etc. facing the atrium. The North facing part contains offices in the perimeter and a corridor facing the atrium. The design phase started in March 1994 and building was completed November 1996.

Figure 9 Window design in the Tax Office at Enschede.

There are two kinds of windows in all offices- a ribbon of low level vision windows and a ribbon of high level daylight windows. The window size is different in the North and the South facing offices, although the glazing ratio is 34% on both elevations.

In a North facing office there are four vision windows (0.8 x 1.2 m²) and two daylight windows (0.7 x 1.9 m²). There are manually controlled external Venetian blinds on the vision windows and no solar shading on the daylight windows. All glazing is clear low energy double glazing with an U-value of 1.6 W/m²K, a light transmittance of 0.77 and a solar transmittance of 0.65.

Figure 8 Elevation of the Tax Office in Enschede.

The window design On both the North and the South elevation of the new tax wing the main part of the offices are designed for two people. Such a standard office is EC2000: Windows - the Key to Low Energy Design

In a South facing office there are four vision windows (0.95 x 1.2 m²) and two daylight windows (0.7 x 1.5 m²). There are manually controlled external Venetian blinds on the vision windows and internal light shelves (0.9 m deep) situated between the vision windows and the daylight windows reflecting daylight to the ceiling and back into the room. The light shelf is placed a few centimetres from the wall. In this way daylight can pass between the wall and the shelf preventing glare caused by differences between the dark area under the shelf and bright surfaces illuminated by the sun or the artificial lighting system. The glazing is medium reflecting low energy glazing with a U-value of 1.3 W/m²K, a light transmittance of 0.66 and a solar 9

Energy Comfort 2000 Information Dossier

Windows - The Key to Low Energy Design transmittance of 0.33.

As a result of daylight simulations with the “Radiance” software the area of the daylight windows was increased in the final design, compared to the area first proposed. Figure 10 shows a visualisation of the daylight conditions in a room in the Tax Office.

Avax S.A. for its own use. The site is situated in downtown Athens in a location where it will be very exposed to the sun.

The building is orientated along a North South axis with the two main facades facing East and West.

The gross area of 2950 m² is divided between three basement levels, a ground floor, three identical office floors, and penthouses with roof gardens at the top. Most offices are situated along the highly glazed East facade separated from secondary rooms like kitchen, toilets and stairways by a central corridor dividing the building into two halves.

The design phase started in 1993 and the building will be completed in the spring of 1998.

Generated by Esbensen Consulting Engineers

Figure 10 "Radiance" visualisation of the daylight conditions in a room in the Tax Office in Enschede.

The vision windows can be manually opened, but because they are inwards swinging it can interfere with the office use. The floor to window height is 0.85 m in all offices.

Artificial lighting is provided by compact fluorescent down lighters situated under the light shelf (task lighting) and under the acoustic ceiling in the middle of the office room. Both are controlled to respond to daylight levels during the day and automatically switched off at the end of the day.

Manual override is provided by local wall switches.

Figure 11 Elevation of the Avax Office Building in Athens.

The window design In a standard office in the Avax building the floor to ceiling height is 2.7 m, the depth 3.0 m and the width 7.0 m. The following description corresponds primarily to the window design in such an East facing office. Figure 12 shows the window design.

Calculations show that the total annual energy consumption for heating, lighting, ventilation and control facilities will be around 60 kWh/m². This is less than half of the consumption of a traditional Dutch office building.

Case 4: The Avax Office Building in Athens This Headquarters office building is being constructed by the private contracting company

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EC2000: Windows - the Key to Low Energy Design

Energy Comfort 2000 Information Dossier

Windows - The Key to Low Energy Design shading devices applied to the windows on this elevation.

All glazing is clear double glazing with a U-value of 2.5 W/m²K, a light transmittance of 0.75 and a solar transmittance of 0.72.

Significant reductions are expected in the energy consumption for artificial lighting due to the use of light fittings with low voltage and high efficiency lamps. The general lighting is automatically turned on/off in response to daylight levels in the rooms. In addition presence detectors will ensure that the lighting is switched off after a given period when the occupants have left the room. Manual override is provided by infrared remote controls. The task lighting is under the direct control of the users.

Figure 12 Window design in the Avax Office Building in Athens.

Because of the hot climate in Greece and the exposed site, great effort has been put into the window design and the design of the solar shading system.

This has culminated in a design with windows divided into a lower vision window and an upper daylight window. The total height is 1.7 m with the vision window accounting for approximately 67%.

The glazing ratio is 45% on the East elevation and only 10% on the West elevation. The distance from floor to window is 0.9 m.

Special solar shading devices have been designed to shade the middle office floors on the East facade.

The devices are fixed white horizontal metal grate grills and movable vertical fritted glass panels rotated by the BMS in response to room temperature and solar radiation. Manual override is also provided via infra-red remote controls. The top and the first floor will be shaded by conventional Venetian blinds controlled in the same way as on the middle floors. In addition to that creepers will form a permanent shading on the penthouse windows on the top floor. All windows are manually openable.

The Avax Office Building is expected to consume around 90 kWh/m² energy per year for heating, ventilation, lighting, cooling and control facilities.

This is only the half of the consumption of a traditional office building in Greece.

Case 5: Lisbon Expo’98 Multipurpose Pavilion Lisbon Multipurpose Pavilion is a 20 000 m² building integrated in the Expo’98 area, located close to the Tagus river. The building will provide facilities for different kind of events like concerts, congresses and sport.

The building is egg shaped with a slightly curved roof supported by concrete columns. Toilets, shops and building management facilities are situated in the perimeter of the building behind the spectators stands. The building is shown in Figure 13.

The design phase of the pavilion started in early 1995 and construction will end in 1998.

As the West facade is situated quite close to the neighbouring buildings and has little glazing, it has slight exposure to the sun. Therefore there are no

EC2000: Windows - the Key to Low Energy Design

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Energy Comfort 2000 Information Dossier

Windows - The Key to Low Energy Design Case 6: Bang & Olufsen Headquarters, Denmark.

Figure 13 Elevation of Lisbon Multipurpose Pavilion.

The window design The purpose of the Expo’98 building is quite different from the other EC2000 buildings which all have office functions or the like. The window design is therefore also very different. In fact the openings that allow most daylight to the public area in the middle of the building are skylights rather than sidelights.

The skylights accounts for about 30% of the roof area covering the public area and are placed centrally in the roof, thereby securing a even distribution of daylight into the space. Between events natural daylight should therefore be sufficient during training, maintenance and general activities.

As a part of the ventilation strategy of the building some of the perimeter skylights can be opened by the BMS, allowing stack driven natural ventilation between the events. During events when the building is displacement ventilated, the skylights will still be open so polluted air can escape out of the roof.

To prevent overheating and glare during warm days the skylights are equipped with motorised external blinds activated by the BMS. All glazing is of medium reflective double glass with a U-value of 3.2 W/m²K. Artificial lighting is provided by low energy lamps on/off controlled in response to daylight levels in the pavilion and switched off when there are no activities in the building.

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The new Bang & Olufsen Headquarters (B&O) in Struer, Denmark is a 5000 m² building comprising offices, exhibition areas, auditorium and canteen.

The building is constructed next to the production facilities of the company in the Western part of Denmark. The project phase started in August 1996 and the building was completed in the spring of 1998.

The building complex is divided into three parts, arranged around a green area situated in the middle.

In the following most attention will be paid towards building 1.

Building 1 is a rectangular three storey office building. The building is raised from the ground standing on concrete columns and walls (see Figure 14 and Figure 15) thus no ground floor exists. The two main facades face South and North (towards the green area). The office area is basically an open plan area, which is divided into smaller sections by movable partition walls around two metres high.

The gross width of the building is 8.25 m of which 1.5 m is the corridor situated at the edge of the floor next to the North facade. The floor to ceiling height is 3.08 m.

Building 2 is situated perpendicular to building 1 with facades facing West and East (green area).

There are two office storeys and a basement. In addition an exhibition hall, two storeys high, is situated on the East side of the building. The facade of the hall is fully glazed.

Building 3 is situated opposite building 1 with the green area between (building 2 connects the two buildings). The main facades face South and North.

The building is divided into two storeys and a basement comprising the main entrance of the complex, a large auditorium, a large canteenkitchen area and several meeting rooms.

The window design The North facade of building 1 is fully glazed (see Figure 15) with low energy glazing which has a Uvalue of 1.0 W/m²K, a light transmittance of 0.77 and a solar transmittance of 0.65. The reason for EC2000: Windows - the Key to Low Energy Design

Energy Comfort 2000 Information Dossier

Windows - The Key to Low Energy Design choosing glazing with such a low transmission coefficient was that with the large glazed area and with normal low energy glazing, it would be impossible to satisfy the Danish building requirements concerning heat loss.

lamps which are automatically turned on/off in response to occupancy in each office section (presence detectors). Manual override is provided by local wall switches. All occupants have task lighting under their own direct control.

The low U-value is accomplished by combining a low energy coating with a krypton gas filling and a large cavity between the glass sheets.

The B&O Building will fulfill the energy requirements set by the national Danish building regulation BR-95.

The large North facing glazed area was chosen to allow plenty of glare free daylight into the building.

Due to the orientation the glazing will not result in overheating .

Ventilation

The South facade of building 1 has a much lower glazing area than the North facade (see Figure 14 and Figure 16). The glazing ratio is around 30% of the gross facade area. The window system is divided into a 0.96 m high ribbon of vision windows and a 0.22 m high ribbon of daylight windows situated just under the ceiling. The distance from floor to windows is 0.94 m and 2.84 m respectively. The vision windows are manually openable and the daylight windows are automatically controlled by the BEMS (see ‘ventilation strategy’).

The glazing is low energy glazing with an U-value of 1.4 W/m²K, a light transmittance of 0.77 and a solar transmittance of 0.65. The main difference between the glazing on the South facade and the glazing on the North facade is that argon is used as gas filling instead of krypton. This type of glazing is used on all other facades in the B&O complex except for the North facade of building 1.

No solar shading is provided on the North or the South facade of building 1, but the vision windows on the South facade are prepared for a BEMS controlled internal solar shading system.

The auditorium, the canteen, the kitchen, the meeting rooms and toilets are traditionally mechanically ventilated.

The office area in buildings 1 and 2 and the exhibition hall in building 2 are naturally ventilated.

In the exhibition hall low and high level automatic vents ensure adequate ventilation.

In building 1 a low ribbon of BEMS controlled openable windows are placed on the North facade (see Figure 15). When open, outdoor air is induced into a small floor plenum where the air is pre-heated by a ribbed pipe system. From this point the air flows to the office area where it is induced by the displacement principle. Driven by stack and wind generated low pressure the air is then extracted via roof vents through the centrally placed staircases.

Mechanical back up is provided by fans situated in the roof vents. The design air change is 1.5 h-1 during the day. During the night the system is closed except during night cooling in summer where extra windows are opened on the South facade. The design air change for this situation is 3.0 h-1.

The whole system of opening of windows and vents, speed of the back-up exhaust fans and temperature of inlet air, is controlled by the BEMS. The office area in building 2 is ventilated in the same way as building 1.

On the West facade of building 2 and parts of the South facade on building 3, fixed solar shading is provided by the outer block work (basalt) covering around 40% of the glazing area (see Figure 17 and Figure 18). Except for blackout curtains in the auditorium there is no extra solar shading on the windows of the complex.

General lighting is provided by high efficiency

EC2000: Windows - the Key to Low Energy Design

13

Energy Comfort 2000 Information Dossier

Windows - The Key to Low Energy Design

Figure 14 South facade of B&O building 1.

Figure 17 West facade of B&O building 2.

Figure 15 North Facade of B&O building 1.

Figure 18 View from inside of West facade of B&O building 2.

Figure 16 View from inside of South facade of B&O building 1.

14

EC2000: Windows - the Key to Low Energy Design

Energy Comfort 2000 Information Dossier

Windows - The Key to Low Energy Design Summary of principles used in the case study buildings APU

Leeds

Enschede

AVAX, Athens

Lisbon EXPO’98

B&O building

4

4

4

Triple glazing

4

External shading

4

4

4

Light shelves (internal)

4

4

4

Automatic window control

4

Manual window control

4

4

Atria for cross ventilation

4

4

Separate windows for vision and daylight Complex shading (controlled

by BEMS)

4

4

N/A 4

4

4

4 4

N/A 4

4

N/A

4

4

4

4

References 1 Pilkington Product Catalogue.

2 DANVAK Grundbog H.E. Hansen, P. Kjerulf-Jensen, Ole B. Stampe DANVAK ApS, 1987

3 Solar Technologies for Future Buildings J. Luther, K.Voss, V. Wittwer Fraunhofer Institute for Solar Energy Systems ISE Conference paper for 4th European Conference ‘Solar Energy in Architecture and Urban Planning’ Berlin 26-29 March 1996

Acknowledgements The authors would like to acknowledge the contribution of all those involved in the EC2000 projects mentioned as case studies in this dossier, and also: • Mr P Monby, Birch & Krogboe Consulting Engineers, for input concerning the Bang & Olufsen building.

• Mr Carl Axel Lorentzen, Pilkington Floatglass, Denmark, for commenting on this Dossier.

Legal Notice Neither the Commission of the European Communities nor any person acting on behalf of the Commission is responsible for the use which might be made of the information contained within.

EC2000: Windows - the Key to Low Energy Design

15

E N E R G Y

C O M F O R T

2 0 0 0

Project information will include

Cross project activities include

> >

>

> > >

Individual project profiles; Information Bulletins on a range of technical and operational subjects; Newsletters; Displays and models; Slide sets.

> > >

design workshops and information exchange; environmental assessment; cross climate thermal modelling; design and performance comparisons and reporting.

C O N T A C T S Project Coordinators

Technical Coordinator

Experts

Simon Burton ECD Energy and Environment Ltd Brussels Office Rue Abbe Cuypers 3 1040 Bruxelles Tel: 322 741 2442 Belgium Fax: 322 734 7910 Email: ecdebru@ibm.net

Henrik Sorensen Esbensen Consulting Engineers Teknikerbyen 38 DK 2830 Virum Denmark Tel: 45 45 834224 Fax: 45 45 836834

Chiel Boonstra W/E Consultants Crabethstraat 38j Postbus 733 NL-2800 AS Gouda The Netherlands Tel: 31 182 683434 Fax: 31 182 511296

Emilio Miguel Mitre EMMA Paseo Zorrilla 98, 7 E 47006 Valladolid Spain Tel: 34 83 221330 Fax: 34 83 220898

Architects G. Daher, F. Guy, R. Inglesakis ATELIER 9 Architectes Urbanistes Associes 54 Rue Sainte Victoire 13006 Marseille France Tel: 33 91 37 9900

Consultant Halcrow Gilbert Associates Ltd Burderop Park Swindon SN4 0QD Tel: 44 1793 814756 U.K Fax: 44 1793 815020

I N D I V I D U A L

S I T E

A N D

Site Number 1 Lisbon Expo 98, Atlantico, Portugal Promoter Atlantico Marechal Gomez da Costa 37 1800 Lisboa Tel: 3511 831 9717 Portugal Fax: 3511 837 3952 Architect Skidmore Owings & Merrill 46 Berkeley Street London W1X 6NT Tel: 44 171 930 9711 U.K. Fax: 44 171 930 9108 Regino Cruz Arquitectos e Consultores, LDA Rua Prof. Ricardo Jorge, 3A Miraflores 1495 Lisboa Tel: 3511 410 3996 Portugal Fax:3511 410 7140 Services Engineers Louis Malheiro da Silva Estrada da Torre 79-85 1700 Lisboa Tel: 3511 757 7822 Portugal Fax: 3511 759 9564 Site Number 2 The Queen’s Building Anglia Polytechnic University, Chelmsford, UK Promoter Mel Barlex Anglia Polytechnic University Victoria Road South Chelmsford Essex CM1 1LL Tel: 44 1245 493131 U.K. Fax: 44 1245495943 Architect and Energy Consultants ECD Architects Ltd ECD Energy and Environment Ltd 11-15 Emerald Street London WC1N 3QL Tel: 44 171 405 3121 U.K. Fax: 44 171 405 1670

C O U N T R Y

C O N T A C T S

Services Engineers Ove Arup and Partners 13 Fitzroy Street London W1P 6BQ Tel: 44 171 636 1531 U.K. Fax: 44 171 465 3669 Site Number 3 Schiedam Public Building, The Netherlands Jan Deenik Municipality of Schiedam Postbus 61 NL 3100 AB Schiedam The Netherlands Tel: 3110 246 5555 Fax: 3110 473 7504 Architect Hans Ruijssenaars Archtectengroep b.v.

Prinsengracht 483 1016 HP, Amsterdam The Netherlands Tel: 3120 6221965 Consultants Peutz and Associes 6585 ZH Mook Postbus 66 Lindenlaan 41 Molenhoek Tel: 3180 58 5017 The Netherlands Fax: 3180 58 5150 Site Number 4 Universite d’Aix en Provence, France Owner Rectorat Aix en Provence Agent Serge Jaure GEST 120 Avenue des 2 Ponts Cazilhac 34190 GANGES Tel: 33 4 67 73 8907 France Fax: 33 4 67 73 8549

BUILDINGS COMPLETED

1993

• ANGLIA POLYTECHNIC UNIVERSITY LRC

1994

Architect Ruurd Roorda Rijksgebouwendienst Directie Ontwerp & Techniek Postbus 20952 2500 EZ The Hague Tel: 31 70 339 1882 The Netherlands Fax: 31 70 339 5030 Energy Consultants W/E Consultants Crabethstraat 38j Postbus 733 NL-2800 AS Gouda Tel: 31 182 683434 The Netherlands Fax: 31 182 511296 Site Number 6 Leeds City Office Park, UK Phil Kirby British Gas Properties Aviary Court Wade Road Basingstoke, Hants RG24 8GZ Tel: 44 1256 308803 U.K. Fax: 44 1256 308799 Architect, Engineers and Cost Consultants Mike Jeffery Foggo Associates 55 Charterhouse Street London EC1M 6HA Tel: 44 171 490 4040 U.K Fax: 44 171 490 2889

>

>

Site Number 5 Tax Office, Enschede, The Netherlands Promoter Etienne Schoenmaeckers Rijksgebouwendienst Directie Oost Postbus 9202 6800 HC Arnhem Tel: 31 26 3713800 The Netherlands Fax: 31 26 4458204

For information about Thermie Targeted Projects, you can contact Mr A Landabaso, Directorate-General for Energy (DGXVII), European Commission, 200 rue de la Loi, B-1049 Brussels, Fax: 32 2 2950577

EC 2000 STARTS JULY

Bioclimatic Consultants ArchiMEDES 120 Avenue des 2 Ponts Cazilhac 34190 GANGES Tel: 33 4 67 73 8907 France Fax: 33 4 67 73 8549

> • LEEDS OFFICE

1995

Site Number 7 Avax Office, Athens, Greece Promoter Mr. Constantine Kouvaras AVAX S.A. Skoufa 64 10680 Athens Tel: 301 364 4561 Greece Fax: 301 364 7265 Architect Alexandros Tombazis Meletitiki – Alexandros Tombazis and Assoc 27 Monemvasias GR-15125 Polydroso Str Amarousiou Tel: 301 6800 690 Greece Fax: 301 6801 005 Consultant Protechna Ltd Tositsa 17 106 83 Athens Greece

Engineers Team M-E Consulting Engineers 15-17 Sarantapihou St. GR-114 71 Athens Tel: 301 361 3641 Greece Fax: 301 364 3253 Design Project Inteco Building, Valladolid, Spain Promoter Gerardo Hernandez Garcia Edificios Inteco s.I. Arco Ladrillo s/n Edif. Centro Madrid – 3 – 1o 47008 Valladolid Tel: 34 83 47 5612 Spain Fax: 34 83 23 8008 Architect and Energy Consultants Emilio Miguel Mitre EMMA Paseo Zorrilla 98, 7 E 47006 Valladolid Tel: 34 83 221330 Spain Fax: 34 83 220898

>

> • RGD ENSCHEDE

1996

• SCHIEDAM PUBLIC BUILDING • MMSH AIX-EN PROVENCE

1997

Tel: 30 94 33 0069 and: 30 18 83 9174 Fax: 30 18 83 9653

EC 2000 FINISHES DECEMBER 1998 • LISBON EXPO 98 • AVAX SA OFFICE

1998