Building intelligently

What makes a building intelligent? Alison Luke reports on the need for an holistic approach and the importance of facade engineering to the MEP services design.

ANALYSIS, MEP

What is an intelligent building? Ask many people today and the question is likely to invoke talk of electronic devices and so-called 'smart' technologies that enable central control of various parameters such as lighting and temperature. But is this really the answer?

The term smart building is now frequently used to describe properties that contain these technologies, but a true intelligent building involves much more. "Intelligent buildings is one of those terms that has been misunderstood for many years," stresses Pantelis Kouzis, overseas business development manager for EKA Group. "There are a number of definitions for an intelligent building...it's not black and white."

The building envelope has a major impact on the energy consumption of any building.

The European Intelligent Building Group (EIBG) defines an intelligent building as: 'one that provides a productive and cost-effective environment through the optimisation of its four basic components - structure, systems, services and management - and the inter-relationships between them...focussing on creating the desired indoor environment to maximise the efficiency of its occupants and allow effective management of resources within minimum life costs.'

The EIBG goes on to say that such buildings should incorporate the best available concepts, materials, systems and technologies, integrated to maximise the performance of the occupants and building operation throughout the entire life cycle. In other words, an holistic approach must be taken throughout the design and construction of a building in order that it will continuously provide optimum performance.

"An intelligent building is one that is always fully leased," adds Kouzis. "The key word is flexibility...intelligence is about long-term investment and an intelligent building is a collection of technologies that are able to respond to organisational change over time."

The overall aim of "intelligent" designing is to reduce the operating costs of a building while maintaining indoor air quality and providing a suitable working environment. To ensure the successful integration of all a building's features, the entire design team must be involved throughout the project.

Surface design

One of the biggest factors in the optimisation of a building's operation is the external facade. As well as being integral to the overall aesthetics, the facade contributes greatly to the technical performance of a building and has a significant effect on the overall energy use.

"The building envelope has a major impact on both the indoor environment and the energy consumption of any modern building," reports Mikkel Kragh, environmental engineer with consultancy Arup. Whether a full glass facade or a mix of cladding materials is used will have a huge effect on the capacity of the MEP services required within a building.

An intelligent building design manages thermal transmissions gained through windows and walls as part of the overall energy balance. By designing the structure effectively, the amount of mechanical and electrical plant needed to maintain indoor air conditions can be reduced, as by lowering the thermal gains through the facade less cooling will be needed to maintain set point temperatures.

In addition, by maximising the amount of daylight entering, less electrical energy will be needed to provide artificial lighting; plus, the heat gains from lighting will also lower, further reducing the cooling load. "In hot climates you want light but not heat gain - you want to get better daylight into the space to reduce the artificial lighting needed, but you don't want the thermal gains [associated with sunlight]," stresses George Berbari, ceo of DC Pro Engineering.

Many of the latest buildings incorporate facade engineering as an integral part of the design process. On the Atkins-designed Iris Bay development for example, glazing has been minimised on the east and west elevations where potential solar gains are highest, to reduce solar gain and glare, the fully glazed facade faces almost north. And with the increased emphasis on sustainability in the region, facade engineering is becoming even more important: "This is one of the most important parts of a building to get right to achieve a green building," states Stuart Clarke, associate, Arup. "It's [glazing] that emits heat into the building," stresses Arthur Millwood, technical manager, Emirates Glass.


Glazing options

So what are the options for facades? Numerous products exist, including various metal cladding systems and different types of glass. Both the individual materials and the combination of these will affect the thermal resistance. "The frame is the weak point of a facade system in terms of weathering and thermal transmittance," adds Clarke.

There are two main groups of glass: reflective and coated 'clear' versions. To date the reflective versions have proved more popular in the region. "[In the Middle East] a reflective glass has a lot of benefits; it's cheap and reflects sunlight [out of the building]," states Clarke. The changing use of buildings in the region though will play a part in the future of glazing: "It's easier to use reflective glass on an office than residential properties and now there are more mixed-use towers being built we must start to look at this," Clarke adds.

One of the downsides of using reflective glass on residential properties is the mirror effect that can be created indoors in certain conditions. "With low light transmission glass you end up with 40% indoor reflectivity," explains Jean Lelievre, general manager for Al Abbar Architectural Glass. "If you go below a certain level you end up with a mirror indoors and this is unacceptable in this market, where properties have been sold on the basis of their view."

An increase in the use of clear glass is already taking place, with architectural fashions playing as big a part as advances in the technology of thermal coatings. "There is a trend in the market towards the use of a more transparent glass with less reflectivity," confirms Millwood. "It's been changing for around three years now throughout the Middle East."

The masterplan for the Dubai International Financial Centre (DIFC) development cites the use of clear glass virtually throughout, reports Lelievre. Architectural design guidelines for the project state that glazing used should be non-reflective and coloured glass should be avoided. In addition, all south-facing planes of glass must be a minimum of 500mm from the face of the building 'to give an appropriate environmental response and reduced heat load'. A maximum external reflectance of 20% and relative heat gain of 350W/m2K are also specified.

The ability to use such a product while maintaining low internal heat gains is down to the coatings. "With coatings [applied to the glass] you can bounce out infrared light and allow as much visible light as possible through. If you can drop the amount of infrared [entering a building] significantly you get huge benefits in terms of less heat and plenty of natural light, so you need less energy to light the space," explains Clarke.

"Light is energy and the more light you let in, the more energy will come in. It's down to the coatings [to control this gain]," adds Lelievre. "The dream of coatings now is to get light in with the best shading co-efficients."

There are now numerous products available that produce low levels of thermal gain. Al Abbar Architectural Glass offers a number of such low-emissivity glass products. CoolRay and e-Cool are designed to maximise energy efficiency and provide high light transmittance with a neutral colour; both feature double or single silver coatings. "We have developed a double silver layer glass coating which has a high light transmission and a good solar factor. This is for residential use, so it's highly transparent from the outside but lets a lot of light," explains Lelievre.

V-Kool also offers a clear glass coating aimed at architecture that requires high visibility and minimum heat gains. The product is claimed to remove 94% of infrared radiation and 98% of ultraviolet radiation, while allowing over 70% of visible light into a space.

From Emirates Glass, the EmiCoolSun NN Series range of low-emissivity coatings have a neutral silver appearance when applied onto clear glass. Four coatings are offered in this range, all providing solar resistance and thermal insulation, high light and a low internal reflection to give the appearance of clear or tinted glass when viewed from inside.

But as well as the choice of facade, the orientation of the building and any additional devices used will also play a part in the thermal gains. "The building must be orientated to deal with the local climatic conditions and sunshades used only where they are actually needed," stresses Clarke. East and west-facing glazing is subject to particularly high solar heat gains and potential glare. North-facing planes are generally favoured for glazing as the sun is at a 45'° angle to the plane; on the south facade the midday sun is at virtually 90'° to the building.

"[In this region] using external shading works very well...by playing with shade you can reduce the energy directly hitting areas and reduce the reflective temperature," explains Clarke. "The orientation is a huge issue and as long as there is space on a site and it fits into the masterplan it's easy to make a difference [with the building orientation]."


Standards

Guidance on the design of facades is available and Dubai Municipality has set standards, which are also being referred to in other parts of the region. "The DM66 regulation was introduced after [the UAE] signed the Kyoto agreement," explains Lelievre. "This was good, as for the first time we had a benchmark to work from...it imposes for both glass and aluminium sections of facades, the minimum requirement for thermal penetration," he adds.

Various developments around the region are, like DIFC, imposing their own additional specifications on which products can be used for facades. In addition, the US Green Building Council's Leadership in Energy and Environmental Design (LEED) and ASHRAE's Advanced Energy Design Guide provide information on design strategies suitable for the use of glass in warm climates.

Further updates on standards are expected within the foreseeable future. "We're expecting Dubai Municipality to make the codes stricter and personally I believe that these codes will change in the near future," concludes Millwood.

DM Decree 66/2003 in brief

On 1 April 2003, the Dubai Municipality-issued Resolution 66 came into effect. DM Decree 66/2003 provides technical specifications for the thermal insulation and rationalisation of power consumption in air conditioned buildings in Dubai. Article 7 of DM Decree 66/2003 relates to the selection of glazing for facades and is aimed at minimising solar thermal heat gains.

Walls and external roofs

Heat resistance and thermal insulation materials must be used so that the overall transmission coefficient does not exceed a U-value of 0.44W/m2K for the roof and 0.57W/m2K for the walls.

Glass openings

If the glass space such as openings or permanent glass with no back-insulated wall ranges between 10-40% of the external wall space double-glazing or equivalent must be used to ensure a maximum U-value of 3.28W/m2K and shading co-efficient of 0.4.

If the glass space is over 40% of the external wall space or in the case of skylights, the maximum U-value permitted is 2.10W/m2K and the maximum shading co-efficient is 0.35.

If the glass is designated for showrooms the maximum U-value allowed is 2.50W/m2K, and maximum shading co-efficient is 0.76.

Aluminium strips should be insulated by using a thermal break system when the opening space is over 40% of the external wall area.

• Specifications for buildings issued before 1 April 2003 but still under study are encouraged to adapt to the regulations where possible. Any specifications issued after this date that do not comply are subject to penalties.

 

Taking active measures

With the emphasis on facades as an integral part of a building's MEP services, the design of the system is as important in reducing heat gain as the type of material used. Arup is currently engaged in a project with several international firms to develop an integrated facade system, with particular emphasis on the frame material.

Another firm is taking this level of integration a step further. Abu Dhabi-based Reem Emirates Aluminium is currently constructing a mock-up of an active facade system that will directly integrate the building envelope with the operation of the MEP services. "An active facade consists of two glass units separated by an air cavity, between which there is an adjustable shading device. This creates a cavity into which air can be drawn from the room and exhausted at the top," explains Imthias Mohamed, r&d engineer with Reem Emirates Aluminium (REA). "This is intelligently connected to a mechanical exhaust."

Active facades are used extensively in Europe, but have yet to be utilised in the Middle East. In REA's system several building components will be integrated, a ventilated double facade forming part of an overall system.

"Most facades today try to eliminate solar heat gain by using various forms of reflective glass, low-emissivity coatings, argon filling or external shading devices," states Mohamed, "Our system will allow light to enter via solar-controlled blinds and clear double-silver, double-glazing on the exterior surface. It will trap the solar radiation in the central cavity using a perforated blind and exhaust hot air via a specially designed ducting system attached to the top of each curtain wall panel," he explains. "The addition of these fixtures to a facade will decrease the U-value from 1.9W/m2 K to 1.04W/m2 K and allow approximately 40% less solar heat gain to enter the room. By incorporating other technologies such as chilled flooring, chilled ceilings, light emitting diodes and building management systems, further energy savings are possible."

The intention is to create a full-size mock-up that incorporates all the technologies to gain actual test results. REA will be working with other research firms and manufacturers of intelligent building components to create an integrated building solution. To co-ordinate the different disciplines and provide a on-stop-shop for clients, it is setting up a company called IBSM - Intelligent Building Systems Management.

In addition to the active facade, the system will comprise various components. A floor cooling system will support the transfer of heat through radiation. A chilled beam air conditioning system will also be included, and an intelligent mechanical ventilation system will be adopted, in which air flows at 40m3/h, entering through the bottom of the facade and exhausting via a chimney-shaped outlet. The entire ventilation system is designed to maintain a laminar airflow with a Reynolds number of less than 2000.

Light emitting diodes will be used for the lighting, reducing the heat build-up from artificial lighting and providing energy savings of up to 75% compared to the use of incandescent lamps. Finally, the entire system will be controlled and monitored by a bms in order to ensure the efficient control of operations.

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