Dubai's great pyramid
The Raffles Hotel at Wafi City is already making an impact on the Dubai skyline, but how do you service a pyramid-shaped building? Alison Luke reports.
Most of the construction projects taking place in Dubai have a familiar feel.
There are so many high-rise towers being built that any new ones rising from the ground are barely noticed by passers-by.
But one building that is taking shape has made everyone stop and stare.
The pyramid shaped Raffles Hotel in the Wafi City development is making an impact on the skyline in its own way.
Its complex shape has produced an MEP design as interesting as the architecture and has acted as a catalyst for an upgrade of the services across the whole site.
Ron Coulter, building services manager for client MKM Commercial Holdings explains: “Raffles is our biggest project on the Wafi site, so its been a good opportunity for us to take a fresh look at how we do some of our services.”
One of the areas reviewed was the air conditioning systems for the development, which bincludes several bars and restaurants as well as a large shopping mall.
An upgrade here has involved the construction of a district cooling system, which has since won a Silver Leadership in Energy and Environmental Design (LEED) Award from the USA’s Green Building Council.
The selection of the system followed a time-cost analysis.
“We looked at the 20 year profile and compared buying in the [chilled water] to making it ourselves and in the end we chose to build our own district cooling systems,” explains Coulter.
Raffles will use around two-thirds of the 4,500TR capacity of the first phase.
The remainder will serve the mall, replacing the dry coolers currently installed.
The plant has been built as close to Raffles as possible to reduce the pipe runs.
“One of the major costs of a district cooling system is the cost of purchasing and running pumps, so the less volume of water you have and the less distance you have to pump it around, the more economical it is,” explains Coulter.
“On the primary loop there is about 100m3, which by district cooling systems is very small.”
This close analysis and value engineering of systems was typical for all services and the hotel overall.
The entire construction team was brought onboard at design stage so an holistic approach could be taken.
This has led to a more efficient and cost-effective design.
“A typical example is that in the original design we had three boilers and four calorifiers, by re-evaluating the systems we’ve moved away from steam boilers to gas, which is more economical, and were able to reduce to two boilers and three calorifiers,” explains Coulter.
“In doing this we were also able to help the structural engineer because the weight of boilers and calorifiers full of water is pretty big, so they were looking at some fairly hefty structural beams and columns to support all this; we were able to reduce that static load quite considerably.”
The hotel shape was also under scrutiny during this design phase, while remaining within the development’s Egyptian theme.
The pyramid shape began life with a square base, which changed to a triangle and was later adapted with three “cheese slices” were removed, so from above it resembles a camera tripod.
There are 18 floors in total, which include 248 guest rooms, a spa, and ballroom.
It is topped by three levels of restaurants and bars.
The use of district cooling for the air conditioning meant that plant could be kept to a minimum and no large plantrooms were needed inside the hotel.
MEP plant areas are located at three levels and these also contribute to the hotel design.
“We’ve used plant areas as acoustic buffers between quiet areas of the hotel and noisy areas, whether it be a bar or nightclub,” explains Coulter.
The scale and shape of Raffles meant that standard hotel services design had to be adapted.
“We’ve had to work quite hard at getting the services in there,” stresses Coulter, “With the complexity of a pyramid shaped building you can’t for example have standard risers in each quadrant or one in each corner.”
A central riser around the lift core serves the upper levels of the hotel, but for the lower floors another solution had to be found.
“We’ve had to provide services up to a certain level in the wings to try and spread the load out,” explains Coulter.
“From around level six down, the runs from the centre to the edges would be so long that we’d have huge flow losses.”
To cater for this, individual risers have been included on each of the wings specifically to serve the outer edges of the lower floors.
The height of the pyramid and inclusion of highly-serviced nightclubs at the tip of the pyramid brought their own issues.
The three-storey top section is glazed, bringing a potential increase to the air conditioning load.
“We’ve had to get more than the normal amount of chilled water up to a high level and the mere fact that we’ve had to take such a large volume right to the very top had an added load,” explains Coulter.
Counteractive methods have been used to reduce these loads such as the use of low emissivity glass and graded flecking of the glazing at the upper levels.
“Everything to try to get better u-values,” assures Coulter.
The initial design stage also played a large part in maximising the energy efficiency of the building’s systems.
“We spent a lot of time looking at the design and twisting the building around on the site to see how different aspects affected the load on the services,” says Coulter.
In addition, Australian firm Vipac was hired to examine building dynamics such as solar gain and acoustics.
As part of it’s input, Vipac created a 1:500 scale model of the hotel to check the effects of wind.
“This gives accuracies of less than 1 m in terms of being able to calulate structural loads,” explains Coulter.
Such checks ensured that the hotel was positioned in the optimum way to prevent wind affecting the guests.
Balustrades have been included around the edge of the site.
Decorated in Egyptian hieroglyphs, to the layman these appear to be purely decorative, but they are acting as wind and acoustic breaks, pushing the sound and air up to a higher level.
The electrical services on the Wafi development are also being rejuvenated by the latest construction.
A complete new 11kV ringmain has been added to the site.
There are two hv rooms with four transformers of 8MW in total, from these the supply feeds two lv rooms.
Currently this feeds the Raffles hotel and phase five of the shopping mall.
“On the original system there wasn’t a ringmain, it was more an impromptu radial circuit,” states Coulter.
“What prompted the ringmain as well is that a new 132kV substation has been built alongside the site.”
This is feeding the adjacent Dubai Healthcare City as well as the Wafi development.
“DEWA started years ago at 11 kV then increased it to 32kV, we changed a number of leads on here from 6.6 to 11kV to cater for that and now they’ve upgraded the whole thing to 132 kV, so on the lv side of the board there are now a lot of breakers and that’s allowed the overall design to produce a new ringmain,” explains Coulter.
The upgrading of the electrical provision for the site, like the air conditioning, will be a gradul process.
“A classic example is we made the original 3 x 1000kVA transformers redundant when those cables came out and the new system will have four x 1500kVA on the ringmain,” explains Coulter, “so gradually we will have a different philosophy for our hv, but it will be years before we get back to some of the older hv rooms.”
The entire ringmain is installed and is expected to be made live within the next few weeks.
“One of the things that was interesting is the amount of effort in getting all the IT structured wiring systems in position,” says Coulter.
A system of Category 5 and 6 cabling has been installed throughout to provide the smart home technologies expected in a Five Star hotel.
Everything from interactive tv, video-on-demand, lighting and temperature controls have been provided in each room.
“We’ve got systems that allow the controls to correlate with the two-port valve in the ceiling fan coil when the temperature is changed; electronic locking systems; systems that allow wireless communications for staff…there’s a staggering amount of Cat5 and Cat 6 cabling being laid,” stresses Coulter.
“In this part of Dubai there are no structured cabling systems, so we have a dish farm on one of the internal rooms that won’t visually impinge on the hotel,” he adds.
The Wafi development has a fibre optic network throughout, which is used for applications ranging from accounts to the building management and security systems.
This will also serve the hotel.
“Two sides of the ring will swing into the Raffles Hotel, so all of the services will be interactive,” Coulter confirms.
“We’ve recently brought in the Nortel telephone system also, so the site is already one step up from the hotel and Raffles will have Nortel when ready,” he adds.
With 248 guest rooms to cater for and the additional services that this includes the increase in the demand on the sewerage system has not been ignored either.
The construction team has worked with Dubai municipality to include a 1.5m diameter network that will also serve some areas of Dubai Healthcare City.
Around 60-70% of the MEP services have been installed in the hotel to date.
Installation has been completed on a floor-by-floor basis to enable areas to be completed to meet a phased programme for the addition of “wild air”.
This, explains Coulter, involves gradually cooling down the building to enable the finishing trades to begin work.
“That has to be carefully co-ordinated with other trades like joinery and soft furnishings because you can’t put those in until you have the humidity and temperature levels stabilised,” he explains.
“There’s a correlation between how the services are installed and set to work and how the other trades interrelate to that.
In hotels more so because they have a lot more soft fittings going in from day one than an apartment or office block,” he adds.
“It takes a long time to do the fit-out so you need quite a long lead time to have all of this air conditioning working.”
Raffles Dubai is due to open to the public in mid-2007 and will be operated by Singapore-based Raffles International.