Proven Flexible Environment Solutions for offices - Do we Care? Do we CARE ENOUGH
Over the years we have seen many different air conditioning and ventilation systems offered up as the new and all serving solution with which to create the perfect office environment.
Very often however these solutions are developed from the “pure engineering” point of view whilst it is my opinion that solutions should offer a far higher level of consideration of the overall requirement, including speed and cost of construction, reliability, adaptability, comfort, ease of maintenance, energy consumption, and so on.
The problem is, that as engineers, we seldom if ever have the chance to repeat a building and hence improve on aspects of the design found wanting; and if we get that chance, we are more likely to repeat the formula than modify it for fear that change may bring other unforeseen problems.
Latham in his report to government stated “If you keep on doing what you always did – You will keep on getting what you always got"
One of our clients, Mr Clive Dorney, Principal Engineer for the Land Rover Group, in interview on the subject of his new Design Facility stated:
“It is very difficult with air conditioning systems to satisfy all the people all of the time. We are an organisation that needs to absorb change, (change in use and change in layout), very quickly and in these days of environmental friendliness, energy efficiency had to be taken into consideration in our decision process.
We wanted to try and keep as many people as happy as possible. It is normal with an air conditioning system, particularly in a deep space office such as this, that you could quite normally get 30% or more of people saying that they are not fully happy with the environment they are in, from a temperature point of view. But we didn’t get anything like that level of complaint - in fact more like 98% of people, when surveyed, were quite happy with their environment, which is quite an incredible performance really.”
So what is this system to which he refers?
Under-floor air conditioning
Since the Egan Initiative much has changed in the commercial world with the one exception of seeking cheaper ways to do the same thing.
Sadly the saying “They don’t build them like they used to” hangs in the air, as client after client learns the painful truth that what seemed like a good cost saving benefit, in one area, impacts badly in other areas.
Sir John Egan’s team however has been able to make comparisons.
With an ongoing programme of airport perimeter construction his team was able to play with a project they called the Component Based OFFICE PRODUCT. From the basic design, first commissioned at the World Business Centre at Heathrow, they were able to make changes across the design concept, to study the impact on cost and time that each different solution offered.
In 1997 BAA commissioned Reid Architecture and Roger Preston Consulting Engineers to consider improvements that could be made to the OFFICE PRODUCT, with the intention of achieving a variety of goals.
The Challenge:
To reduce cost and time - increase certainty and value
1) Reducing Cost Extended project time and delays directly
affect profitability.
2) Greater value - Ensured by satisfying Customer expectations. directly affect pr• Ensure we satisfy customer
.
What did they achieve?
1. The World Business Centre, Heathrow
Comprises two buildings, WBC1 and WBC2, both speculative office buildings of 6000m2 each and both air-conditioned using fan coil systems.
The buildings are 4 floors high with a floor plate in the order of 1500m2.
The total height of each building is 16m to the roof level, with a plant room of 4m in addition.
The space is well served with toilets and lifts and the space is totally speculative awaiting unknown tenants with unknown requirements. Internal headroom is 2.7m
2. First Point, Gatwick
At First Point the building plan was, originally, virtually identical to WBC, but changes in the choice of structure and the air conditioning system permitted an increase in the size of floor plate to an optimum 1750m2 per floor because they had a consent for a specific volume of building and with the height saving offered by the AC system BAA were able to increase the floor plate and achieve a greater net lettable within the same specified volume. The planners accepted this and BAA was able to maximise the return on the site, together with an increase in available head room of 70mm. The air conditioning system offered dramatic savings in height of the building and program timesavings.
In situe cast concrete at WBC was changed to totally off-site fabricated modular concrete frame that offered time savings and greater accuracy.
The air conditioning system was changed to a Hiross zonal under-floor system.
The immediate and most noticeable cost benefit came from the 300 mm saving in height per floor. Visually, the removal of the deep false ceiling gave cleaner lines to the façade and, at fit out stage, enabled Tenant’s demands to be more easily and quickly met. The Client, BAA, estimated savings in excess of £260,000 in curtain walling alone, together with savings of £600,000 due to reduced construction time.
A comparison between the WBC2 and First Point revealed some interesting figures offered from the building managers.
year built Design Time Construction Time Cost to build
World Business 1998 20 weeks 39 weeks £90.63/sq ft
Centre
Heathrow
First Point 1998 19 weeks 38 weeks £79.95/sq ft
Gatwick
Endeavour House
Stansted 1999 17 weeks 30 weeks £77.00/sq ft
Just as a reminder, the WBC buildings have a traditional fan coil system, while the other two buildings utilise the Hiross Flexible Space System. The Client, BAA, was so pleased with the outcome at Gatwick that they immediately commissioned another similar building at Stansted, transferring the full design and construction team from one job to the other.
BAA are firmly convinced that they can reduce the build time even further and estimate that 25 weeks is an achievable target, provided only that the Hiross Flexible Space System is used. As can be seen above, the savings in construction costs are dramatic.
Further cost benefits are gained from an earlier rental income stream and reductions in the cost of initial fit-out and subsequent tenant changes.
Roger Preston - Consulting Engineers in Maidenhead UK carried out computer simulations to verify possible energy savings and these have been shown to exist both theoretically and by the reduced electrical consumption recorded in the actual buildings. Measurements of total electrical consumption showed a saving of slightly over 30% using the Hiross Flexible Space System
A recent independent Indoor Air Quality check by Winton Laboratories at First Point indicated that, throughout the building, the systems achieved very even distribution of fresh air and the levels were very satisfactory
System description
Typically an under floor air-conditioning system makes use of the floor void directly as a plenum for the distribution of air. Supply and Return channels are created by means of baffles and Zone units are suitably located throughout the office space to generate conditioned air locally to serve the needs of the space. The Zone unit delivers conditioned air into the floor void supply plenum and draws spent air back through the return plenum and normally serves an area in the region of 200-300 sq m.
The plenum operating pressure is approximately 10pa compared with VAV systems in which operating pressures often exceed 800 pa and thus the under-floor system offers an immediate energy saving in fan power. But this is not the major area of energy saving when compared with VAV.
Building Simulation Ltd have shown by modeling a variety of systems that under-floor air can offer savings of perhaps 25% or more Chilled and Heating water are delivered to the Zone Units by means of small diameter pipe work and condensate water is drained away. The diversified zonal approach reduces the extent of pipe-work within the working area when compared with Fan Coil units whilst offering heating or cooling availability at each zone.
Fresh air may be delivered to the Zone Unit directly from outside or via a central ventilation system. Normally the latter option is utilised as it offers the opportunity to operate heat recovery. Extract air is usually taken away at high level in the space, most suitably near risers.
Let into the floor over supply plena are individually controlled Fan terminals(Fantiles) 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.
Courtesy Liebert Hiross
Return air grilles are positioned in the floor over the return plenum to permit the return of spent air to the Zone Unit for re-conditioning.
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 the Hiross designed Hiromatic advanced controller. All Zone Units and Fan terminals can be connected into the system permitting centralised monitoring and control of various functions to take place.
The control system is the “Heart of the Matter” and a paper in the CPD module of CIBSE Journal Feb 2002 refers. With fan terminals serving in the region of 10-15m2 each it is quite usual to find several thousand terminals in large projects and the need for intelligent monitoring becomes obvious. In a survey carried out for the Swedish National Pension Fund it was found that 78% of office workers in London requested personal control of their environment as the main feature lacking in their office. It is simply not possible to send a team around a building at night to reset terminals that have been adjusted by users to suit differing daytime requirements.
The Hiross control system is usually integrated with a Building Management System to provide suitable levels of monitoring and control. The powerful nature of this Hiross control system facilitates easy connection to most BMS systems.
Floor system
The raised floor is constructed in the following way.
Floor panels are supported on structurally sound pedestals and stringers with electrostatically conductive gaskets. Allied with conductive floor tiles and covering, this ensures that any build-up of static charge is dissipated harmlessly through the floor. This sub-structure provides the structural support for the in-floor Fan Terminals and Return Grilles, where floor tiles are cut to permit their placement, and to provides the support framework for the re-locatable air baffles.
The sub floor is prepared in accordance with the agreed programme by first sealing with a PVA sealant to stabilise the concrete slab, and then marked out to a greater or lesser degree subject to requirements to define pedestal positions. This permits any under floor services to be installed without clashing with pedestals.
Again subject to requirements the services can be laid, or part laid, and the floor installation commenced.
Once laid, the floor is fitted out with Fan terminals and return grilles, along with fire barriers and air segregation baffles. This element may be delayed if a tenant has not been found, with the advantage of cash flow savings.
Comfort:
The concept of floor supply is not new but the way in which the air is introduced into the space may seem surprising at first glance.
Conventional displacement systems throw the air out across the space at low level and are carefully controlled to ensure the supply temperature is maintained at about 3 deg C below room design temperature to avoid draught and resulting complaint. However such systems are generally limited to a sensible cooling capacity in the region of 60w/m2 and demand high volumes of air to be driven up and down the building – often with re-circulation and associated cross contamination throughout the building.
Many offices, dealing rooms and call centers exceed this load of 60w/m2, in some cases by 3 or 4 times. Displacement simply cannot cope and engineers are forced to bootstrap a secondary system, such as chilled ceilings or beams, to add additional cooling.
Sadly, the thermodynamics of such a solution results in a degree of dumping, which in turn carries back concentrated odour, fume etc into the occupied zone. Further more, the height of the space required for satisfactory operation of the displacement system places a demand on building materials and structure resulting in additional cost and construction time and, to a small degree, energy.
Under-floor air conditioning however can meet the need of most comfort environments and, with little change, accommodate heat loads from zero to in excess of 1000w/m2.
In normal office applications the supply air can be offered, with a ∆T between 2 and 3 times that of displacement, from locally positioned zone units permitting far less fan power to be consumed in circulating the air to the point of need. A design ∆T of 10 deg C is quite normal.
Of course, as I said earlier, introducing air in this way is surprising and many engineers doubt its credibility until they feel it for themselves. The amount of air in circulation with displacement systems is high. With under-floor air the amount of air per watt or kW of cooling is much less but the ∆T is higher. For this reason the air must be introduced without affecting users detrimentally.
The traditional swirl diffusers used with displacement ventilation causes the cool air to be blown at low level across feet and ankles. Due to this discomfort risk, the supply air temperature is generally limited to 18 deg C.
Secondly, due to the small amount of air being supplied from each diffuser many more are required with displacement ventilation systems to keep discharge velocities low. The higher the cooling requirement, the more air, and hence diffusers, required.
With Flexible Space Systems, the fantile unit introduces the conditioned air vertically into the occupied space inducing room air. As this flow of air is at room temperature it causes no discomfort to the occupants.
For this reason we approached the Swedish Clinic for Occupational medicine to make the initial studies and, over the years, we have worked with VeSol in Ireland to make simulations and the University of Hong Kong to make physical tests, in order to address the issues of under-floor supply in different climatic regions.
We have found that vertical distribution with natural high entrainment achieves the optimum solution in virtually every situation.
The results are again pleasing but nothing can beat user comment and we have many statements from a wide variety of professionals and user groups.
Managing ChurnAT & T have calculated, that over a forty year building life-cycle the building cost are broken down as follows:
• 11% Initial Construction Cost
• 14% Financing Costs
• 25% Reconfiguration Costs
• 50% Operational Costs
From this it may be seen that reconfiguration and operational costs are by far and away the major expense.
It is my belief that an engineer’s duty is to design systems that take due account of all costs. The cost of re‑configuration whilst maintaining a comfortable working environment should be considered at concept stage where the costs of accommodating this flexibility will be lowest.
The cost of people is steadily rising and legislation is demanding greater care. It places responsibility on all employers to ensure staff work at full capacity and efficiency. It is more likely they will do so in a comfortable and efficient environment where change may easily be accommodated to reflect the task being carried out.
Examples of Churn
Digital in the South of France have stated that “linked to a building management system the Flexible Space System has made savings of 30% in facilities related operating costs”.
Motorola have stated “the maintenance costs are reduced by at least 30%”.
At
Bloomberg in London the facilities company stated that “compared with a similar adjacent building served by Fan Coils the maintenance is reduced from 4 days per week every week to 4 days every 3 months and the user satisfaction is much higher. The system creates a less stuffy environment and complaints of too hot or too cold are seldom expressed”.
At
Panasonic in Paris the General Manager reported a saving in the region of $150 per square metre per annum in direct costs for adapting his building when compared with his old HQ served by Ceiling based Fan Coil units.
The system is quite simply proven, to offer Flexible Environment Solutions for offices, cost effectively.
Further reading:
www.flexiblespace.comwww.buildingdesign.co.ukwww.flexiblespacesystem.com
