Environment: Facade Solar Shading

Introduction - Facade Its Role In Buildings:Facade is the external wall or fabric-covering which wraps the building. It is of primary importance in skyscrapers where it acts as an enclosing filter between the building's interior and exterior.The role of a facade is a complex one and the following objectives need to be considered in its design:

• Energy efficiency (i.e. the building should contribute to the reduction in energy consumption)
• Provision of central daylight to reduce direct and reflected glare
• Minimisation of water penetration and condensation.
• Provision of a choice of colours, textures and finishes
• Compatibility with automated window cleaning equipment
• Ability to accommodate building movement
• Minimisation of loading on the structural frame
• Minimisation of maintenance requirements

Depending on the climatic zone, the design considerations for these components in the bioclimatic skyscraper include solar-insulation and reduction, rainwater collection or discharge, wind and natural ventilation, orientation and buffering, view and relationship with the ground plane at different heights.Passive solar architecture is a consequence of applying passive solar design principles. These include the effective management of solar radiation at the facade and natural heating/ cooling sources which influence the building facade to minimise internal heating,cooling and daylight energy requirements for the occupants' comfort. This is possible through strategies such as appropriate orientation; managing direct heat gain and daylighting ( window and shading0 ; managing indirect gains (thermal control in opaque systems; ventilation; thermal mass as heat sink or source; and other more novel techniques for manipulating indoor comfort.A tall building might be regarded as material led.

The designer has to be careful in the choice and placement of materials from the window and shadings to thermal mass, insulation and openings for ventilation. The fifth facade- or roof- should also have thermal controls for thermal comfort as well as prevention of unnecessary heat gain and loss.'[1]Solar Shading Of Tall Buildings:Ken Yeang in his The Skyscraper-Bio climatically considered discusses about the importance and types of shading required in tall buildings due to their height, skyscrapers are exposed more directly than other buildings to the full impact of external temperatures and direct sunlight. Therefore, their overall orientation has an important bearing on energy conservation.The greatest source of heat gain can be entering through the window.

The direct radiation transmitted varies markedly with the time of the day and the angle of incidence.In the hot and humid tropics, for instance, this remains fairly steady at about 50^ο and drops sharply at 60^ο. Main Openings facing south and north minimise solar radiation and thus the building's air-conditioning load. If the site does not align with sun's geometry on its east-west path, other built components of the site-scraper such as the service core can follow the geometry of the site to optimise column grids in relation to the basement and/or upper-floor car-park layouts, etc.Unless important views elsewhere, the sky-scraper's windows shuld face the directions of the least direct solar insolation in conjunction with the curtain-walling, if this is deemed aesthetically desirable.Some floor plate shaping adjustments or the incorporation of shading devices (eg.

Sunshades, recesses or balconies, etc) may be needed for those site locations which lie further north or south of the equatorial belt.For aesthetic reasons, the fully glazed curtain wall may be used on the non-solar facing facades but on the hot east and west sides some form of solar shading is required, making due allowances for glare and the quality of light entering the spaces. For instance west wall in the tropics (and south-west in higher latitudes) has the highest intensity at the hottest time of the day.'[1]The External Wall as An Environmental Filter or Sieve:The external wall of a skyscraper should be regarded as a 'sieve' than a sealed skin. These should function as a permeable membrane with adjustable openings.

Ideally, the skyscraper's external walls should act like a filter that has variable parts to control good croos ventilation, provide solar protection, regulate windswept rain, and discharge heavy rain.The thermal forces acting on the outside of the skyscraper include a combination of radiation and convection impacts. The radiation component consists of incident solar radiation and of radiant heat exchange with the surroundings. The convective heat impact is a function of exchange with the internal air and may be accelerated by air movement.

The exchange effect may be increased by diluting the radiation over a large area by the use of curved surfaces such as vaults, domes, atria and louvred or irregular surfaced roofs which will, at the same time, increase the rate of convection transfer.Wall surfaces which have direct solar insolation must be shaded. Their cladding material's insulation and 'time-lag' characteristics should be taken into consideration. External material used might be those that are effective heat-sinks (eg. aluminium composites) or be designed to have a double layered ventilation space.Another very effective protection against radiation-impact especially in external wall design, is the selective absorptivity and emissivity characteristics of a material, especially under hot conditions.

Materials which reflect rather than absorb radiation, and which release the absorbed heat as thermal radiation more readily, bring about lower temepartures within the building.[1]Solar Shading Options:Sunshading can be in the form of rectilinear design (in early buildings) - such as vertical fins - and horizontal projections, or a combination of the two, known as 'egg-crate' Le Corbusier invented the 'brise-soliel' to make the principle of 'free facade' tenable in hot climates.These devices are used for the purpose of reducing the heat load of the building through its enclosing envelope.These louvers can be fixed or movable. If fixed, the salient angle depends on the latitude of the site and the aspect of the window. The louvers can exclude summer sun and admit winter sun. They can be designed to exclude the sun all round the year (eg. in the tropics).

In the southern hemisphere, horizontal louvers with the diagonal section are suitable for the northern aspect as the sun angles are high, and vertical louvers are suitable for the windows with a southern aspect due to low sun angles to the east or west. Thus the diagonal louvers combine vertical and horizontal shading for the complete exclusion of the sun. The tilt of the louvers may be adjusted to admit sun during prescribed periods as desired, such as winter of the temperate climate.'[1]Importance Of Non-Glazed facades in Ken Shuttleworth's words:Influenced by Mies van der Rohe and the International Style, architects have been fascinated by fully glazed tall buildings for decades.

Today these high-energy, gas-guzzling, glazed office blocks can be found in virtually every large city in the world, regardless of climate, orientation or site characteristics.The problems with the fully glazed building skin are well documented; spaces can overheat from excess solar gain in the summer, yet suffer massive heat loss in the winter which if compensated for solely by mechanical conditioning, leads to excessively high building energy consumption. Typically, the architect's solution to these issues - incorporating elaborate shading devices to reduce solar gain, adding ventilated cavities with opening slots and then protecting the shading from dirt and increased wind speeds at height with a further layer of glass - result in a faade design that is both complicated and expensive.

In comparison, a well insulated building skin with increased levels of opacity and punctured windows where daylight is required would offer an improved energy performance at a greatly reduced cost.Furthermore, this style of construction would arguably result in a significantly reduced embodied energy of the building envelope. New regulatory requirements - responding to climate change issues - will also impact on the design of the high-rise building skin. In the UK, the latest edition of the Building Regulations part L [3] makes strict demands governing the energy performance of new buildings.

This makes the design of completely glazed tall building skins more difficult than ever to achieve.Instead of finding a way around these regulatory hurdles, we as designers need to be using our vision and creativity to generate building skins that not only comply, but go above and beyond these requirements. The key to this challenge is the incorporation of increased quantities of opacity within the tall building facade.'[2]A new approach with non- Glazed facade in tall buildingsKen Shuttleworth says [2] , If our aim is to design low-energy, sustainable tall buildings, the starting point should not be a building skin that is entirely transparent. Tall buildings need greater quantities of mass and solidity within their skin, backed by liberal amounts of insulation. In light of this, the starting point for most high-rise projects should be around 50% solid, with windows located and sized appropriately for daylighting and views out.

Obviously natural light penetration is important - reducing artificial lighting loads and improving occupant comfort - but we need to strike a balance between this transparency and thermal performance.At Make the arcjitects are exploring new ways of integrating reduced levels of transparency in tall buildings without creating repetitive, unimaginative faades. For example, the envelope of the Spiracle Tower (see Figure 1) consists of flat, rectangular anodised aluminium panels applied in undulating horizontal bands which emphasise the stacking of the floors. The result is a rippling effect, with solid cladding extending downwards to create thin glazed slots for bedrooms and opening up to enable views out from generous balconies that lead into living spaces.

The facade of the 28-storey Kite Tower in Leeds (see Figures 2 & 3) will consist of approximately 50 percent glazing to give the best balance between view, daylight and heat loss and gain, whilst still maintaining a high degree of interest and excitement within the building envelope. A further strategy employed by Make has been to utilise the building form to influence its faade performance. The Stellar Tower - a 255m high proposal for Abu Dhabi - uses a sculptural form as an integral part of its environmental strategy.

The building shape expands outwards towards its top, offering the largest floorplates for the upper storeys where demand and rent is greatest (see Figures 4 & 5). This in turn creates a faade that is inclined away from the sun, minimising solar gain whilst still ensuring that all floors enjoy optimum natural light and views.Case Study - The Menera Mesiniaga:The Menara Mesiniaga is the headquarters for IBM in Subang Jaya near Kuala Lumpur. It was first conceived of in989 and finally completed in 1992. IBM asked the office of T.R. Hamzah & Yeang for a building which was a high-tech corporate showcase for their highly visible site and high-technology industry.

Also, Ken Yeang designed this building as an example of his bioclimatic skyscraper practices and principles.The building is an environmental filter, an analogy for synthesis and analysis.The Menara Mesiniaga is a built work that utilizes a basis of traditional Malaysian building models and their transition or evolution into modern principles. It is Yeang's vision of the tropical garden city and it uncovers the relationship of buildings, landscape and climate... transforming the impact of highrise development in the ecosystem of a city.Function and UseThe building is equipped with 6- classrooms, a demo center, a 130-seat auditorium, lounge, cafeteria, and prayer rooms. The building boasts an excellent audiovisual system, complete lighting equipment, administrative and catering services and a large entry foyer for product display and demonstration. It is wired for communications within itself and with its technology partners.

They boast a commitment to creating a facility that would be sensitive to and in harmony with the local environment, as well as one that reflected the company's aspirations to be an industry leader.Technical DataHeight - 63 metersFloors (over ground) - 14Floors (under ground) - 1Year started - 1989Year completed - 1992Gross Floor Area - 6503 m sqSite and Climate:Subang Jaya is near Kuala Lumpur in Malaysia. The climate is considered tropical. The year round temperature, heat and humidity are fairly similar throughout the year.

The day and night temperature vary little.Artificial landscape was created to shelter and insulate the lowest three levels from the morning sun. Parking is located below the building and berm.Menara Mesiniaga is located on a major highway from the airport to Kuala Lumpur. It is in a highly visible location with few buildings within the surrounding context. Main Ideas and ConceptsSky gardens that serve as villagesSpiraling vertical landscapeRecessed and shaded windows on the East and WestCurtain wall glazing on the North and SouthSingle core service on hot side - EastNaturally ventilated and sunlit toilets, stair ways and lift lobbiesSpiral balconies on the exterior walls with full height sliding doors to interior officesThe building is 15 stories tall and circular in plan.

Yeang designed this building to include three items: a sloping landscape base to connect the land with the verticality of the building; a circular spiralling body with landscaped sky courts that allow visual relief for office workers as well as providing continuity of spaces connecting the land through the building; the upper floor provides a swimming pool and gym.Shading DevicesThe facade is a sieve-like filter (instead of a sealed skin). The louvers and shades relate to the orientation of the building. They allow or reduce solar gain. The deep garden insets allow full height curtain walls on the north and south sides- as a response to the tropical overhead sun path. The core functions are located on the hot side, the east.

Sun Shaders Garden InsetsIn Rethinking the Skyscraper [4], by Robert Powell, critic Charles Jencks discusses a new synthesis for contemporary architecture that is responsive to the climate of a particular place and finds inspiration for a new architecture language from forces that are ultimately cosmic.(48)The Fifth Facade- The RoofThe roof is inhabitable. As part of Yeang's fundamental idea of connecting the building back to land - the roof holds a pool and a gym. The roof acts as the capping social space of the building as well as an additional buffer between interior and exterior spaces. The sun screen structure is made of steel and holds aluminium panels.

The structure is capable of holding solar panels (if ever installed). The screen shades the pool as well as the roof of the building. The rain water collection system is also on the roof. The roof is not problem free. Because of the high-humidity, the insulation has deteriorated and there has been some leakage.

Elsewhere in the building some rusting has occurred. Yeang has since stressed an importance on material life-cycle costing.ConclusionYeang says 'An ecological building should not be a weapon in a retreating battle. On the contary, it can contribute postively to the environmnet. A green area is a productive area.

So the building can geerate energy instead of consume it.Tall buildings are exposed to the full extent of heat, weather and temperatures. The overall building orientation has an important bearing on energy conservation. In the tropics, North and South faced opening reduce the need for insulation. Deep recesses may provide shade on the building's hot sides.

Large multistory transitional spaces serve as in-between zones and allow air flow. External walls should be permeable with adjustable openings, filter- like. Walls can provide solar and weather protection, as well as provide for cross ventilation.

Yeang explains that the plan should reflect the patterns of life an culture of the place. Plantings should travel vertically to generate oxygen and help cool the building. Passive solar shading is generally located on the east and west sides in the tropics. Cross ventilation should let fresh air into the buildings even in air conditioned spaces.The design of the tall building facade is at the forefront of a change.

The fully glazed, totally transparent office block is dead, a thing from the past when regulations were more lenient and our attitude to the environment more naive. The design of the tall building faade needs to incorporate more opacity, more solidity and more insulation, with windows strategically located where natural light penetration is actually required, as opposed to simply wrapping every inch of the building skin in glazing. In conjunction with this, emerging technologies such as vacuum cladding and nanogel will offer increased faade performance that will assist in reducing the energy consumption of tall buildings.The challenge then, to the architect, is to explore the possibilities of increased levels of opacity in the high-rise skin, designing exciting tall buildings without simply reducing them to dull, monotonous boxes with repetitive square punctured windows.

In turn, the challenge to the glass industry is to respond to a reduction in the specification of glazing by giving us a massive improvement in its performance.In conclusion, it is important to emphasise that energy efficiency in architecture should not beapproached programmatically, with the application of a fixed series of design solutions. Rather, it calls for a considered and wide-reaching questioning process which permeates every level of the design process and which takes into account the unique qualities and characteristics of each individual site.'[2] References:[1] Ken Yeang, 1996. The skyscraper Bio climatically considered - a design primer, Great Britain, Academy Editions[2] Ken Shuttleworth, RIBA, 2008 Form and Skin: Antidotes to Transparency in High Rise Buildings, Ctbuh 8th World Congress 2008[3] ODPM. (2006).

The Building Regulations 2000. Approved Document L2A. Conservation of Fuel and Power in New Buildings Other than Dwellings: 2006 edition. NBS, London.[4] Powell, Robert. 1999 Rethinking the Skyscraper: The Complete Architecture of Ken Yeang. New York: Whitney Library of Design[5] Arcidi, Philip. Menara Mesiniaga Tower.

Progressive Archtitecture. v. 74, March 1993: 108-110.[6] Richards, Ivor. Tropic Tower. Architectural Review. v. 192, February 1993: 26-31.Websites:www.skyscrapers.com (Menara Mesiniaga)www.mesiniaga.comwww.smartarch.nl (Ken Yeang / Menara Mesiniaga)www.ellipsis.com (projects-Menara Mesiniaga)www.archnet.org