New Home for the Home Office
The Home Office is a principal government department servicing United Kingdom residents in a number of ways, including crime and drug prevention, immigration and nationality issues, counter-terrorism and community activism. Up until now, assorted Home Office departments were scattered in buildings all around Westminster in London, but thanks to a dedicated team of designers and developers, acti...
The Home Office is a principal government department servicing United Kingdom residents in a number of ways, including crime and drug prevention, immigration and nationality issues, counter-terrorism and community activism. Up until now, assorted Home Office departments were scattered in buildings all around Westminster in London, but thanks to a dedicated team of designers and developers, activities have been consolidated in the new Home Office Building, a site encompassing 75% of an entire block in the city of Westminster, near the Houses of Parliament.
Procured as a private finance initiative (PFI), the project was undertaken by a consortium of private developers—Bouygues Construction and Bouygues' sister facilities management company, Ecovert FM—contracted by the U.K. government to design, build and operate a 73,000-sq.-meter building on behalf of the government for 29 years through a contract valued at
By choosing the PFI route, the government was ensured cost and program guarantees before committing to the project, as well as being ensured that construction would continue over the contract's lifetime.
But before the project could get underway, an extremely detailed agreement, including extensive key performance indicators (KPIs) that prescribed exactly how the building was to operate and perform, was needed. This took more than five years to negotiate.
For example, the temperature in the ministers' offices was specified within an acceptable range. If temperatures go beyond this range for 15 minutes or more, penalties will be levied on the developers.
Flack + Kurtz (UK) and Battle McCarthy were appointed mechanical and electrical engineers for the project. As a design, build and operate contract, it would effectively mean that they serve as the contractor's in-house design team.
Moreover, as a government project, the building would require energy-efficient, highly sustainable M/E systems. In addition, because carbon emissions are strictly regulated in Europe, a heat-pump system would be used to provide office spaces with heating and cooling.
Working with such a detailed contract, the engineers found themselves continuously referring back to the agreement and the KPIs to ensure specification accuracy.
Lay of the land
The new Home Office is actually three buildings—Fry, Peel and Seacole—connected at the lower ground level and also by enclosed bridge links on levels 1 through 4. Fry and Peel stand eight stories high, while Secole has six levels. Each building has a full-height atrium and an open street plan providing continuous circulation between the three buildings through the bridge links.
Each building is serviced in two halves with a service core containing lifts, stairs, toilets, mechanical plant rooms, electrical risers and IT distribution rooms.
Above lower ground, the building comprises offices, meeting rooms and a 200-sq.-meter computer room. Peel's ground floor houses the main entrance, conference rooms, a TV and radio studio and press briefing room. The lower ground level houses a kitchen/restaurant, recreation rooms, a backup 200-sq.-meter computer room, storerooms, printing rooms, a library and facilities rooms. The lower ground level also has a car park and loading bay.
Plant services are located on the roof of each building with the central plant located at the lower ground level.
With a 34-month design and construction program, work commenced immediately after the contract was signed in April 2002, with the demolition of existing 1960s 100,000-sq.-meter high-rise buildings and WWII bunkers, formerly occupied by the U.K. Dept. of the Environment.
As a government building, the facility was expected to earn a BREEAM "Excellent" rating. BREEAM is similar to the U.S. Green Building Council's LEED program, with scoring based on energy performance, sustainability, building construction methods and management, and the resulting environment for the occupants. An Excellent rating would be comparable to the LEED Platinum rating. The project was monitored through design and construction, and enhancements such as additional lighting controls and energy-recovery systems were added to ensure compliance.
The campus is supplied by an open-ring, 11-kV supply-rated input at 5 MVA. The ring supplies double-ended, packaged substations in each building, backed up by 11-kV standby generation.
Distributed generation to each building provides standby power for life-safety systems and 10% of the building systems. Due to the cable lengths involved, duplicate step-up transformers, 400-volt/11-kV, are used to distribute standby power to the 11-kV ring. Life-safety system transfer switches are supplied at 400 volts directly from the generator synchronizing panel.
A power-management system manages the building loads into 36 steps through building management systems and switchgear to ensure the load matches the generator capacity in the event of a generator failure. The power-management system also controls high-voltage system switching after a utility failure and allows short-term parallel connection with the utility for a no-break return to utility supplies.
To meet the construction program and avoid problems associated with a shortage of skilled electricians in London, the contractor decided to use pre-manufactured wiring systems. Consequently, distribution boards were delivered pre-wired to modular wiring sockets mounted at the top of distribution boards. Pre-wired and pre-tested distribution boxes with up to nine circuits each were installed in ceiling voids and plugged into the connectors on the distribution boards. From here, modular wiring connectors supply lighting-control modules fixed in the ceiling voids and sockets for cleaners and vending areas.
Energy metering is provided on most main circuits and all distribution boards to meet energy-conservation requirements. In addition, the meters are networked back to the building-management system for remote reading. The M/E engineers also developed a strategy to enable the meter readings to be downloaded to a spreadsheet to allow periodic review of energy efficiency, in accordance with one of the KPIs.
A look at lighting
Also with sustainability in mind, the placement of atria in each building and careful attention to the depth of plan helped maintain the optimal layout to achieve the intended daylight performance.
Similarly, all office spaces are provided with natural light and views to the outside. However, because the ceiling system was defined at 500 × 500—rather than the more common 600 × 600 grid—the options for lamp and luminaire design were narrower.
A networked lighting control system is provided to all areas, comprised of lighting-control modules in ceiling voids, motion and daylight sensing and local override switches. Some areas were also provided with dimming. In addition, the lighting-control modules have 10 plug-in ports allowing for simple reconfiguration of lighting arrangement in the event of partition moves.
Security lighting is provided in office areas with override switches on each level to disable motion sensors in order to avoid activating lights on frequent guard tours.
In the arena of fire protection, the full-height atria in the buildings essentially dictated that each building would be a single fire compartment. The buildings are therefore arranged for single-phase evacuation, and fire separation between the buildings allows for evacuation of each building independently.
The fire-detection system consists of distributed fire-alarm panels with addressable loops. In addition, a distributed voice alarm/public address system was provided for evacuation messages.
The fire-detection loops also control fan and plant shutdown, smoke evacuation fans and dampers, and cold smoke evacuation actuators on perimeter windows. (For more information on smoke control for the Home Office, go to the csemag.com Fire Community.)
A firefighter's telephone system is provided in firefighting shafts, and an intercom is provided in each disabled refuge. Both communicate back to the fire command center.
The facility's sprinkler system serves all parts of the building with the exception of the roof plant enclosures. The unmetered incoming fire main connects to two half-capacity break tanks with a total actual capacity not less than 160 cu. meters. The storage tanks serve the booster set, which then connects to the sprinkler main serving the installation alarm valves located in the ground floor valve chamber. An alarm valve is dedicated to each building.
Moving over to the mechanical side, the systems were developed only after extensive building environmental analyses were carried out using computer modeling and simulation of the environmental loads.
Ultimately, the systems were designed with the following objectives:
Low-energy installations that afford energy transfer between zones and buildings providing a building that requires a thermal energy input only when a net imbalance exists.
High-efficiency fa%%CBOTTMDT%%ade design treatment that reduces solar gains and heat losses while maintaining a good level of natural daylight within the workspace.
Large primary plant systems generally confined to areas remote from occupied areas to provide better access to plant maintenance and minimize noise and nuisance.
Firefighting and emergency smoke-control systems provided for life safety, which includes an automatic sprinkler system throughout and a gaseous fire-suppression system in specialized computer rooms.
Emergency smoke control and mechanical air pressurization of the escape routes for life safety.
Environmental conditioning to the general office areas is provided via an energy transfer system, which comprises a number of reverse-cycle heat pumps connected to an energy transfer distribution medium.
The energy transfer medium is low-temperature water, which typically ranges between 29°C (84°F) and 35°C (95°F), via high-efficiency, reverse-cycle heat pumps utilizing electrically driven, hermetic scroll-type compressors. Localized water/air heat pumps are located in distributed plant rooms at each core.
Thermal energy is only added to or rejected from the energy transfer system when an overall energy imbalance exists in the system. Heat rejection is achieved via six closed-circuit cooling towers located at roof level of the Fry building, and heat input is provided indirectly via a gas-fired boiler plant located within a designated boiler room at basement level in the Fry building.
The primary plant also serves the air-handling plants for the offices and ancillary areas, chilled water plants for ancillary support areas, heating for ancillary support areas and air conditioning for IT suites.
Pressurized pipework distribution systems were provided to serve the primary heat rejection system, primary pumps serving the energy transfer system, primary heating pumps serving the low-temperature hot-water heating system and primary chilled-water pumps serving ventilation systems.
Primary ventilation to the office areas is derived from the air-handling plant located within external plant areas at the roof level of each block.
Primary air-handling units (AHUs) are of double-height configuration with the return/exhaust air section mounted on top of the intake/supply air section. Each primary AHU is comprised of intake dampers, pre-filter, pre-heat coil, bag filter, mixing box, thermal wheel (hydroscopic), humidification plant, chilled water cooling and reheat coils, supply and extract fan sections.
Pre-heat coils and reheat batteries use the energy transfer medium. Chilled water for the cooling coils is generated by localized water-cooled chillers, which use the energy transfer medium for heat rejection.
Pre-conditioned primary ventilation air is distributed via a galvanized sheet-metal ductwork distribution system to serve the on-floor AHUs. Generally, each primary AHU serves two vertical risers, each serving approximately one half-floor of each building.
Chilled water for summer cooling requirements is provided by localized water-cooled chillers of the screw-compression type. Chillers utilize refrigerant R407(c) and incorporate all necessary controls for independent standalone operation.
To offset the high ventilation rates due to occupancy densities, independent ventilation and/or air-conditioning systems were specified to serve the auditorium, IT training and conference rooms, entrance foyer, mail room, restaurant and cafe, kitchen, sports and recreation areas, storage and office areas and basement plant rooms.
The ground-floor auditorium, IT training conference suite and sports complex were also designed with variable-volume air-conditioning systems. In addition, supply and extract fans are variable speed with inverter drives. VAV boxes serving these areas each have LTHW heater batteries to provide localized room control. Exhaust air after the energy recovery section is then discharged into the car park.
The computer equipment rooms are pro-vided with packaged, close-control localized air-conditioning units suitable for downward airflow into a pressurized floor plenum system. These air-conditioning units are of the water-cooled DX expansion type, incorporating DX cooling coils, integral R407(c) hermetic compressors, humidification plant and hot gas reheat. Condenser water for heat rejection is derived from the centralized heat rejection system via an independent pumped distribution system.
And last, but not least, a complete integrated building automation system was provided with full automatic control, monitoring and addressing of all the building's HVAC systems. In addition, system software and protocol conversion provides appropriate interfaces to other building systems including: standby generation plant and "load-shedding" systems; security/CCTV fire-alarm and detection panels; lift-installation systems; building life-safety systems; lighting-control systems; and power distribution.
The BAS also offers plant monitoring and alarm differentiation; interactive analysis and automatic scheduling of plant operational set points for optimum energy consumption; energy monitoring and audit; and systems availability and performance auditing.
Home sweet home
Although the stipulations were extensive, in the end, the M/E team worked diligently to achieve the client's objectives, resulting in a comfortable, functional workplace enjoyed by the Home Secretary—a member of the U.K. Cabinet—other Home Office ministers and employees, and visitors availing themselves of the department's services.
The Strictest of Design Criteria
In line with the extensive contractual requirements stipulated by the British government for the design of its new Home Office headquarters, the facility's mechanical system was generally designed to meet the following performance criteria:
28°C dry bulb/21°C wet bulb
-2°C dry bulb/-2°C wet bulb
General Occupancy and Ventilation
1 person per 10m
12 liters/sec./per person
1 person per 2.5m
12 liters/sec./per person
1 person per 3.0m
24 liters/sec./per person
10 air changes per hr., extract only
1 person per 2m
12 liters/sec./per person
3 air changes per hr., minimum
20 liters/sec./per m
24 liters/sec./per m