Ask anyone living in a high-rise apartment block what their home lacks and a large proportion will say a garden. But one scheme in the Dubai International Financial Centre is ensuring that residents don't miss out. Alison Luke reports.
With the price of land in most inner cities forcing a growth upwards, the number of people living in high-rise apartments is increasing at a phenomenal rate. To satisfy end-user demands these properties are being fitted with ever more diverse features, from rooftop swimming pools to smart home technology; and one project in Dubai is now planning to give the ultimate prize to apartment dwellers: a series of indoor gardens literally on their doorsteps.
Although many properties now have roof and ground level gardens, this is being taken one step further at the Sky Gardens development. Garden floors are being created at six levels within an otherwise ground-to-roof level central atrium in the 40-storey block.
Keeping the plants alive while ensuring comfortable conditions for residents has created several challenges for the MEP services. From acoustics to humidity levels, how do you provide enough light and water to maintain a flourishing garden while creating a comfortable living environment for humans?
Sky Gardens is one of three residential buildings planned for the Dubai International Financial Centre (DIFC), and is expected to be the first private development to complete in the DIFC scheme. Construction began on site in March 2005 under the management of Kuwait-based firm Al Mazaya.
WS Atkins & Partners Overseas is employed as MEP consultant on the project. The firm is providing the technical drawings and specifications, as well as being responsible for the supervision of the MEP installation. Kuwait-based Bader Al Mullah won the contract for the MEP works in competitive tender.
"We know and have worked with Bader Al Mullah in Kuwait and that was the reason that they were pre-qualified to bid for this job and compete with other local MEP contractors in Dubai," explains Tareq Dalloul.
The firm began work under a nominated subcontract with main contractor Arabtec Construction during November 2005. "We started our work immediately [after winning the contract] because there was a lot of preconstruction activities in terms of setting up drawing approvals," explains N Raheja, general manager of Bader Al Mullah's Dubai branch. MEP installation began in June 2006.
Access to the Sky Gardens apartments is via a corridor running around the rectangular central atrium. "There are 16-20 apartments per floor and will be six different elevated gardens at different levels through the atrium," explains Dalloul. "The tenants will have direct access to the gardens at all times and any floor which is above a garden level will have a direct view at all times; there is no raised or glass partition along the corridors concealing the gardens."
Special floors were created to hold the gardens after construction of the main building structure. Underpinned by giant steel trusses welded to the main structural frame, these will be at levels three, 10, 17, 24, 31 and 38.
The main MEP services plant is sited in plantrooms in the building's three basement levels. The use of district cooling to feed the 1,200TR air conditioning needs means that plantroom space is minimised. Javed Magray, senior resident engineer, Atkins Middle East, explains: "DIFC will have its own district cooling system, which is being installed by Empower. We're already in touch with [Empower] re the primary circuit; the secondary circuit will be completed by Bader Al Mullah.
"Additionally the equipment that has been specified for this project is state-of-the-art, so is smaller in size," adds Magray. Chilled water is pumped to plantrooms at the upper levels via 30.4cm diameter pipes in dedicated mechanical services risers around the building.
Electrically there is a substation at ground level feeding from the Dubai Electricity and Water Authority (DEWA) power supply. Here 11 transformers of 1,500kVA capacity feed seven busbars that run the full height of the building to distribute power to local level. The 3,200 and 2,500A busbars are tapped into at each floor as required.
The biggest challenge to the MEP services comes from the garden atrium areas. "This poses the challenge of finding the right equipment to maintain the temperatures and the pressures within that space," explains Raheja. The presence of water, plants and soil adds to the needs of the air conditioning system design and equipment that could be used to maintain comfort conditions of 25-28Ãƒâ€šÃ‚Â°C and 50% relative humidity.
"These garden floors really pose a challenge when you are designing an air conditioning system to keep them cool, because of the humidity and the weather here, with humidity at 100%, everybody would just get wet, so the air conditioning has to be up to withstanding these problems," stresses Magray.
"The air conditioning units were marginally customised," explains Raheja. "It was not off-the-shelf systems that we purchased, they were specially custom-built only for this project. Normally the air conditioning system has a cooling coil, here that cooling coil was of a different specification; we have a lot of heavy-duty to reduce in terms of the gardens."
The air conditioning units are installed on the base of each garden floor, serving the garden below, with air being pushed to the areas needed by use of jet diffusers. "These units are not based in terms of air conditioning tonnage, but more of the cfm of dry air that is sent onto the floor via the jet diffusers. These have got a longer throw, so the air will be able to travel from a very high distance right to the people who are on the garden, so there is a comfort zone present at the garden level," explains Bader Al Mullah project manager H Pai.
The unusual needs of the air conditioning units led to a close involvement between the MEP professionals and manufacturer at selection and approval stages. "We had several meetings with the suppliers and have come to a design or solution with the supplier that best suits the needs of the building," assures Magray. "It wasn't just ÃƒÂ¢Ã¢â€šÂ¬Ã‹Å“let the supplier do what they want', it was discussed thoroughly and we arrived at a system that was best for this application," he adds.
Further consideration for the air conditioning system was the acoustics. "The equipment used must give the least amount of disturbance to the tenents," stresses Magray, "The selection of the equipment has been made from the brands that are in the market, but there are certain ones with reduced noise and some that produce no noise at all, so we've gone for the best options," he adds.
To reduce the building's operating costs, heat recovery systems have been incorporated throughout the air conditioning design. Reducing the amount of cooling actually required has also been tackled. "[The building] has been insulated thoroughly; thermal blocks have been used and these have a very high thermal insulation," Raheja explains.
"The curtain wall system is designed with an air gap between the panes, which acts as an insulation. Behind the curtain wall there is further insulation, so a lot less cooling needs to be done in this building because the heat losses will be minimal," he stresses. Low emissivity glass of alternating thicknesses of 6, 12 then 6mm has been used for the facades reports Magray.
The lighting design for the atrium is currently being finalised and, like the other services in this area, it requires specialist care. "At the moment we are looking at two options for lighting the atrium: one is indirect lighting where we have the lights on the floor and reflectors on the ceiling; and we're looking at another option that is direct lighting, by basically mounting the lights on the walls," explains Magray. "Most probably we'll go with the option of indirect lighting, which is very unique," he adds. High-powered halogen will be the likely source used.
A combined tank provides domestic water and irrigation water for the gardens, with a separate drainage system provided for the gardens. The amount of water needed will be minimised with careful choice of plants.
Inside the apartments
The MEP services design within the apartments is as thorough as that in the atrium, with user-control and flexibility being top considerations.
"For every room we have a fan coil unit or air handling unit with its own individual control, so that anybody can maintain the temperature of an individual room without having to depend on the next room," explains Raheja. This reduces energy use as cooling can be targeted to the rooms where it is needed; the design provides further benefits to the construction and installation. "This helps in reducing the size of the unit so that we have the maximum amount of space available in the false ceiling. The noise level are also reduced by using these smaller units," Raheja adds.
The electrical and communications systems being installed throughout the development also offer this level of flexibility and technology. A state-of-the-art communications system includes cctv, audio-visual and IP telephone systems and is designed to accommodate Etisalat, Du and Tecom services. In addition, an integrated building management system relays information from fire and smoke sensors throughout the individual apartments and the communal areas to a central control room.
Sky Gardens is due for completion in November 2007.