Return to AET Homepage

 
Recently completed, The Centre in Hong Kong is the worlds tenth tallest building standing over one thousand feet high and offering over one million square feet of office space. The building creates a new landmark in Queens Road Central, Hong Kong.

 
And in Malaysia, the Telecom Tower creates another impressive sight offering 600,000 square feet of space.

These buildings stand out because they are the first "super buildings" to adopt the concept of The Hiross Flexible Space System, and they both offer a chance to study the issues that form the basis of this paper.

In London and worldwide many professional teams are being asked to carry out value engineering studies in an effort to reduce cost and time.

However many of these studies are confined to initial cost savings without necessarily investigating ways to save costs in ownership through life-cycle studies. Why? The answer is obvious: because developers want to maximise their return.

In my opinion the flaw in this approach is that the teams look to make savings in each individual discipline instead of analysing the co-ordination of disciplines. They fail to fully embrace changes in working practice and the demands of modern office technology that demand a different type of building, as well as the demands of users, who are now far more aware of the need for efficient facilities in order to operate effectively in world markets.

Occupiers are now far more aware of the disadvantages imposed on them by poorly designed buildings and they are increasingly prepared to pay a premium for buildings that can show positive operational advantages.

An additional factor is that even in Hong Kong, buildings are now expected to last many more years than they were in the early 1980,s and it is not unrealistic to expect buildings constructed today to have a 40 to 60 year life span. This single factor begs for consideration of the total life cost considerations, which in turn demands a fully flexible and intelligent design, and must place additional emphasis and consideration of the costs of reconfiguration and operation.

• 11% Initial Construction Cost
• 14% Financing Costs
• 25% Reconfiguration Costs
• 50% Operational Costs

The impact of such cost saving decisions often dramatically affects the reconfiguration and operational costs adversely and thus may push up the costs of reconfiguration by several percentage points. Currently initial cost saving practices are still general practice because the extra costs of such decisions are passed on to the as yet unknown tenant and are thus not a penalty to the developer, albeit a penalty to the nation..

If then design teams could be permitted to embrace the additional dimension of reconfiguration cost saving, and if developers could market this benefit effectively to the potential users, those developers may find that they can rent the building at a premium due to the added value of their design and thus improve their return by sharing part of the users operational cost saving over the life of the building and in my opinion benefit greatly in commercial terms. I think in time to come we will see government incentives for such endeavour.

The concept is basically very simple.

Raised access floor with power distribution located in the floor plenum

Plenum beneath a raised access floor

Increasingly, buildings worldwide are adopting the concept of raised access floors for the intelligent distribution of power and data cabling. The wireless office in my opinion is still a dream imagined by data engineers and amusingly accommodated by power engineers and thus I think raised floors will become increasingly more used for some considerable time.

However the general acceptance of the advantages that a raised floor offers for power and data has generally been overlooked by air conditioning and ventilation engineers who continue to argue for clear space in the false ceiling for distribution ductwork in the case of VAV and location of fan coil units. Times are changing though and now Leading consulting engineers and pioneering developers in many countries are already using this raised floor for many services including wave guides, central vacuum cleaning systems, air conditioning and displacement ventilation to great advantage.

The Flexible Space System is basically an under floor air conditioning system making use of the floor void directly as a plenum for the distribution of air.

The raised floor

• creates a plenum
• eliminates or reduces false ceilings
• allows easy access to services
• allows easy component relocation

Because a false ceiling is not required, often the building can have 11 floors in the height otherwise required for ten.

Zonal Floor based System.

 
Supply and return channels are created by means of baffles, and Conditioned Air Modules (CAM) are suitably located throughout the office space to generate conditioned air locally to serve the needs of the particular zonal space. The CAM units deliver conditioned air into the floor void supply plena, and draw spent air back through the return plena.

Alternatively the system can operate using a HIVAR in place of a CAM unit. There are a number of differences demonstrated in the air flow diagram.

Floor Supply - Room/Ceiling Return system (HIVAR)

 
A study carried out last year by Roger Preston & Partners demonstrates the allowances that must be made for heat gains from the building fabric to the supply air temperature. The diagram shows the change in air temperature flowing across a slab of constant temperature taken from a working Flexible Space System installed at a BAA development at Gatwick.

What we can see is that with a velocity of around 2m/s underfloor and with a design flow temperature of 14deg C we can happily operate with a CAM unit placed in the centre of a 30 m zone. However if we allow the velocity to drop to 0.3m/s we see a dramatic increase in temperature pick up and consequently a reduction in the size of zone possible. Hence Variable Volume systems applied to underfloor plenums can have serious problems with temperature pick up by the time the air has travelled to the perimeter of a space where it is needed to do the cooling particularly in low load situations. As a general rule of thumb we try not to exceed twenty metres.

Birds eye view of a flexible space installation

Chilled and Heating water are delivered to the CAM by means of small diameter pipe work and condensate water is drained away to nearby risers.

Fresh air may be delivered directly to the CAM from outside or via a central ventilation system. Extract air is usually taken away at high level in the space near risers.

The fan terminal suspended in the raised floor

The air supply and local controls

Let into the floor over supply plena are individually controlled Fan terminals of either recessed or floor standing configuration. These terminals introduce air into the space above, in accordance with the dictates of their own on board controls system. Each unit has fan speed and temperature set point adjustment and through a fast data link may be controlled from a central point. In a recent survey in London, 78% of office workers polled requested personal control of their environment as a priority.

Return air grilles are positioned in the floor over return plena to permit the return of spent air to the CAM unit for re-conditioning.

 
A computer simulation study has been used to analyse likely air movement and temperature distribution within a modular office using the FTU 450 unit.

Simulation: 0.125m3/s @ Supply Air Temperature X-Axis Slice at 1.00 meter (Slice Ax-Ax) Velocity Slice

 
The building is generally divided up into several zones per floor and these zones are defined by means of fire barriers placed in the floor void.

The whole system is controlled by means of the electronic management system and Hiromatic advanced controller. All CAMs and Fan terminals can be connected into the system permitting centralised monitoring and control of various functions to take place. This may also be integrated with a Building Management System subject to compatibility and requirements.

 
The two buildings mentioned at the beginning of this paper are pioneers in the field of under-floor air conditioning in Asia and follow several years of dramatic success in Europe where such concepts have been operating with surprising/outstanding results in cost, effectiveness and user satisfaction.

The aspect ratio of ductwork and the problems of drumming and support make a 3:2 ratio generally the norm.

 
Now that raised floors are generally accepted for cable distribution we find typical floor to floor heights to be in the region of:

Making a total of 3800mm to an average 4000mm

Now if we consider doing away with the false ceiling completely we can reduce the height by 600mm. If we then consider using the raised floor for ventilation as well as power distribution we must increase the floor void to provide a cable zone and a ventilation zone and we have found that generally a total 300mm void offers all the space that a building ever requires. Thus we find a net saving in height of approximately 450 mm.

This equates to somewhere between 10 and 15 % of the height of a building and we must study the inherent savings that are achieved as a direct and indirect result of utilising the floor void in this way.

1. The savings in the curtain walling materials and all other vertical structural elements due to the height saving and
2. The savings in interest charges on modular equipment, which can be purchased far later in the programme.

In Hong Kong this saving in cost could have amounted to around 6.5 million dollars or 65 dollars per sq m of which some 5 million dollars was saved on Curtain walling alone, the rest being in reduced vertical components including vertical structural elements, lift shafts, stairwells, risers.

Builders generally agree that any solution that permits them to "Get out of the ceiling quicker" reduces management and time and often reduces damage to final finishes, which can also be very costly.

Architects find reduced "snagging problems" and Engineers report reduced commissioning programmes. For example: At the Rover Design HQ in Gaydon, 7 weeks saved on commissioning programme)

 
Together all these advantages offer savings and increased profitability across the design and development teams.

Secondly and still of considerable note the nature of a floor based system permits delivery of key mechanical and electrical elements far later in the programme and in some cases permits the equipment to be supplied at the time of the tenant fit out and thus cash flow and cash demand can be improved, offering savings in interest charges on the development. Taking 20% of the contract to be mechanical and electrical services and perhaps 50% of that element to be purchased 3 months later in the program could offer a further 2.5 million dollars saving.

Normally tax relief/capital allowance stands at 25%. The Capital allowance on a building of 100 000m2 would be 1.5 million dollars and if we consider the average fit out costs of partitioning to be around $200 dollars per linear m we could expect capital allowances on partitioning within the building to at least double the tax relief.

The system makes use of the floor void directly for the distribution of air and thus that air becomes in contact with the concrete slab. Using off peak power tariffs the building manager can run the plant at night and reduce the cost of power, while he cools the thermal mass of the building by a few degrees. This permits the generated cooling load the following day to be absorbed into the slab and thus reduces the demand on the chillers for several hours each day.

Roger Preston and Partners have carried out a computer simulation of this night time cooling performance and find that even with minimum ventilation, considerable energy saving is possible.

NIGHT COOLING STUDY - SUMMARY

The potential benefits of overnight free cooling in buildings have been known for some time.

This study investigates these benefits when used in conjunction with the Hiross Flexible Space System.

A detailed thermodynamic study using TASŪ computer software has been undertaken on an office development at Gatwick Airport which has a Hiross Flexible Space System and mechanical ventilation providing minimum fresh air only for the occupants.

The main conclusions of the study are that during the cooling season in the South East of England there is considerable potential benefit from night time cooling using outside air to:-

• Reduce the sensible room peak cooling load by 9%.
• Reduce energy consumption and CO2 emissions due to the ventilation and cooling systems by 19%.

These reductions would be achieved with no additional capital plant investment; all that is needed is for the Designer to properly specify an

In a report to a Facilities Management conference in Strasbourg the General Manager of Panasonic in Paris reported the results he found in comparing his original building served by ceiling based fan coil systems with his new head quarters building served throughout with the flexible space system as follows.

Panasonic results

In the first year of operation the Facilities manager estimated that he relocated 70% of his work stations to suit changing management ideas and requirements.

Direct invoiced costs of change:

Original Building With Fan Coil System $170-$200/m2 Building with Flexible Space system $17-20/m2 Net saving in cost of change in the order of $167/m2/annum

Building With Fan Coil System 12-16 weeks Building with Flexible Space system 1 week

The savings simply in the cost of reconfiguration equate to the cost of the rent in many offices.

In Hong Kong applying these figures the savings to the tenants in the first year could amount to 15 million dollars. This equates to approximately half the rent in this city centre building.

The reduction in time taken is immeasurable in terms of the increase in staff productivity but is recognised to be very significant by leading organisations.

If we add up all the savings mentioned above we find that the following

Even if we divide the Panasonic findings in half the savings made by the tenants year on year will pay back the average construction project in around 10 to 12 years. With the average life of buildings at 40 to 60 years we can expect the choice of underfloor air conditioning to offer a construction payback in the order of 4 to 5 times.

I believe these figures to be conservative and further I believe that they are so important that no developer can afford to ignore at least the investigation of such advantage on every project. It is the responsibility of cost consultants to fine tune and verify the actual costs on each occasion.

I believe that the above brief paper offers at least an insight into the implications of poor decision making at the beginning of a project and I believe this information makes a valuable contribution to the subject of "Intelligent Building" or as I prefer to call it "Building Intelligently"