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What matters most to different clients
  Speculative
developer		 Institutional
investor		 Developer
investor		 End-user
developer		 Tenants
Space efficiency ***** ***** *** ** *
Quality of specification **** **** **** ***** *****
Air-conditioning ***** ***** **** ** ***(*)
Natural ventilation ** * *** **** **(*)
Ease of maintenance ** *** **** ***** *****
Energy efficiency ** *** ***** ***** *****
Low capital cost ***** *** **** *** *
Low operating costs ** *** *** ***** *****
***** = high priority; * = low priority
Key design criteria for urban offices
BCO specification DL&E survey
Occupational density indoor climate control (m²/person) 14 10-14
WC provision (gender split/m²/person) 60/60@14 m²/person 50/50@14 m²/person
Fresh air ventilation (litres/sec/person) 8-12 12-20
Cooling loads
Small power (W/m²)		 15 15-25
Lighting (W/m²) 12 12-20
Primary power
Equipment (W/m²)		 15-25 15-25
Lighting (W/m²) 12 12-20
Lighting to office areas (Lux) 350-400 350-500
Source: Originally published in Building Services Journal. Based on the British Council for Office’s current standards and a Davis
Langdon & Everest survey of the design parameters of a number of recent commercial office schemes.
Whole-life (net present) costs
of air-conditioning systems
System £/m²
Fan-assisted variable air volume 820
Variable air volume 780
Two-pipe fan-coil unit 680
Four-pipe fan-coil unit 640
Chilled ceiling 430
Displacement ventilation 340
The calculations are based on a City of London office
building with a gross floor area of 10 000 m². Capital costs
are at first quarter 2000 price levels. The net present cost
accounts for initial capital costs, energy and maintenance
costs and, where appropriate, costs of lost lettable area
and the periodic replacement of plant and equipment. The
effects of capital allowances are not accounted for.
Calculations are based on a 25-year period, using a
discount rate of 6%.
Building services installation – shell and core
Cost model based on conventionally engineered solutions         Target costs based on value-engineered solutions      
  element
cost £		 cost/m²
gfa £		 cost/m²
nia £		 % element
cost £		 cost/m²
gfa £		 cost/m²
nia £		 %
Sanitary fittings 72 300 3.29 4.79 1.59 40 000 1.82 2.65 1.42
WC suites, washhand basins and so on (average rate used)       175 @ £300 Revised costs based on a reduced number of sanitary
fittings. Calculations of sanitary appliances based on total
building population rather than on floor-by-floor calculations.
Provisions for increasing toilet capacity by extending toilet
cores into office areas are built into the base building core
design. Additional benefits include an increase in net internal
area. 		     
Disabled WC suites and fittings       7 @ £1000        
Cleaner’s sinks and fittings       7 @ £400        
Allowance for drinking fountains       Item @ £10 000        
Disposal installations 214 600 9.75 14.21 4.72 178 000 8.09 11.79 6.33
Rainwater system Above ground internal: cast-iron drain pipes and roof gullies; connections to below ground drainage; drainage channels       22 000 m² @ £3 Revised costs based on a reduced number of sanitary fittings.      
Soil, waste and vent system; above ground internal pipework, cast iron and PVCu       200 @ £400        
Condensate drainage; pipework and insulation in riser stacks       22 000 m² @ £1.30        
Pumped drainage to basement areas; connections to below ground drainage       4700 m² @ £8.50        
Water installations 172 000 7.82 11.39 3.79 80 000 3.64 5.30 2.85
Cold water service mains incoming water service, storage tank, booster pumps, pipework distribution, water treatment and insulation       200 @ £350 Revised costs based on a reduced number of sanitary fittings.      
Domestic hot water service; local electric heaters; pipework distribution, insulation       90 @ £600        
Drinking water service mains incoming water service, storage tank, booster pumps, pipework distribution, water treatment and insulation       22 000 m² @ £1.50        
Cold water supply to landlord’s areas       Item @ £15 000        
Space heating and air treatment 1 901 000 86.41 125.89 41.85 1 338 000 60.82 88.61 47.62
Heat source; gas-fired boilers approx 1000 kW. Duty, twin-walled stainless steel flues, gas supply       Item @ £47 000 Revised costs based on the following design changes: the use of roof-mounted plant, which reduces the costs of vertical and horizontal distribution to basement plant; the use of modular air-handling plant; the use of direct gas-fired air-handling units – gas-fired AHUs are more expensive than conventional AHUs, which use low-temperature hot water heating, but savings on the LTHW system exceed the additional costs of the base unit; the use of electric heaters for local area heating in areas such as plant rooms, stairs and corridors; the omission of staircase pressurisation (approved by the district surveyor); the rationalisation of riser design. The use of roof-mounted modular plant also results in savings on plant room area, increasing the efficiency of the development. Gas installation costs will increase as a result of the adoption of gas-fired AHUs.      
Chilled water plant; packaged air cooled chillers; approx 2000 kW       Item @ £215 000        
Low-temperature hot water distribution to air-handling plant       Item @ £160 000        
Chilled water distribution to air-handling plant and office areas; pipework, pumps, pressurisation units, water treatment, insulation       22 000 m² @ £15        
Supply and extract ventilation: air-handling plant, ductwork, dampers and insulation; including dedicated air-supply to basement       22 000 m² @ £21        
Atrium air transfer system; fans, ductwork and dampers       Item @ £65 000        
Toilet ventilation; extract plant, ductwork, grilles, insulation and attenuation       22 000 m² @ £3.50        
Car park extract system; fire-rated fans and ductwork       700 m² @ £165        
Smoke extract system to lower ground floor and basement; fire-rated fans and ductwork       4000 m² @ £43        
Atrium smoke extract; roof-level fire rated fans       Item @ £45 000        
Staircase and lift lobby pressurisation: extract fan, ductwork and grilles       5 @ £25 000        
Supplementary ventilation and air treatment to plant rooms       1350 m² @ £50        
Testing and commissioning, operating and maintenance manuals, record drawings       Item @ £20 000        
Electrical installations 1 031 100 46.87 68.28 22.70 384 000 17.45 25.43 13.66
Mains and sub-mains distribution; high-voltage switchgear, transformers, mains and sub-mains cabling and containment; low-voltage switchgear, rising busbar and distribution boards       22 000 m² @ £20 Revised costs based the following changes to the design: main high-voltage distribution panels split and located adjacent to load centres such as main heating, ventilating and air-conditioning plant, saving on the costs of sub-mains cabling to load centres; use of packaged main plant such as sub-stations and generators; use of modular plant can also reduce the costs of plant room construction; use of “plug and play” connections to modular plant, simplifying on-site installations; use of armoured cable instead of cable and conduit, simplifying on-site installation; reduction of lighting load to 9 W/m2; use of “plug and play” connections to luminaires, simplifying installations.      
Standby generator, 250 kVA generator for essential services only; acoustic enclosure, control panel, oil storage and distribution       Item @ £80 000        
Small power; power outlets to landlord’s areas       6900 m² @ £9        
Power supply to heating, ventilating and air-conditioning plant and lifts       Item @ £13 000        
Lighting; switchgear and wiring to landlord’s areas       6900 m² @ £11        
Lighting; luminaires and lamps to landlord’s areas       6900 m² @ £24        
Extra for emergency lighting installation; inverter packs and self-contained units       6900 m² @ £5        
Extra for feature lighting to entrances, lobbies and atrium; external feature lighting       Item @ £150 000        
Allowance for trace heating       Item @ £10 000        
Protective installations 334 600 15.21 22.16 7.37 192 000 8.73 12.72 6.83
Earthing and bonding       22 000 m² @ £2 Revised costs based on the simplification of the sprinkler installation, including the rationalisation of riser design and the location of sprinkler tanks next to the risers.      
Lightning protection       22 000 m² @ £2        
Dry risers including landing valves and inlet boxes       20 @ £1200        
Hose reels       32 @ £1800        
Sprinkler installation (OH3); holding tanks, booster pumps, pipework distribution, on-floor isolating valves; full sprinkler installation to landlord’s areas, blanked connections to tenant’s areas       22 000 m² @ £7.50        
Communications installations 312 000 14.18 20.66 6.87 227 000 10.32 15.03 8.08
Voice/data wireways; cable tray in risers       Item @ £10 000 Revised costs based on the specification of a fire alarm system with single stage/two stage evacuation programmes only, with no voice PA-based phased evacuation function.      
Security installation: CCTV installation, intruder detection, intercom and access control containment       Item @ £60 000        
Fire alarm; fully addressable fire alarm and smoke detection installation to BS5839; phased voice evacuation, including primary distribution to tenant's areas; dedicated phone system       22 000 m² @ £11        
Special installations 330 000 15.00 21.85 7.26 289 000 13.14 19.14 10.29
Building management system; centralised energy management system comprising motor control centres, isolators, starters and all controls, outstations, riser network and monitoring, including head-end equipment       22 000 m² @ £15 Reduced costs achieved by simplifying the specification of the building management system; including reducing the number of control points. Costs of control points on modular plant included in cost of the packaged units.      
Builders work in connection 175 000 7.95 11.59 3.85 82 000 3.73 5.43 2.92
Forming holes, chases and so on; Allow 4%       Item @ £175 00 Reduced costs as a result of simplified shell-and-core installations.      
Shell-and-core total 4 542 600 206.48 300.82 100.00 2 810 000 127.74 186.10 100.00
Building services installation – Category A fit-out
net internal area of 14 300 m2
Cost model based on conventionally engineered solutions         Target costs based on value-engineered solutions      
element
cost £		 cost/m²
gfa £		 cost/m²
nia £		 % element
cost £		 cost/m²
gfa £		 cost/m²
nia £		 %
Space heating and air treatment 1 392 800 63.31 92.24 44.06 1 137 000 51.68 75.30 46.48
Chilled water distribution to fan-coil units in tenant’s areas       14 300 m² @ £16 Revised costs based the following changes to the design:
specification of electric re-heat to fan-coil units instead of
low-temperature hot water heating, resulting in savings
on on-floor distribution and simplification of the fan-coil unit
installation; rationalisation of on-floor ductwork routes;
greater use of flexible ductwork; use of ductwork
suspension systems instead of unistrut; standardisation of
grilles and diffusers.		      
Low-temperature hot water distribution to fan-coil units in tenant’s areas       14 300 m² @ £10        
Fan-coil units; control valves, ductwork, grilles and diffusers in tenant’s areas       14 300 m² @ £70        
LTHW heating to tenant’s ancillary areas       800 m² @ £25        
Electrical installations 1 053 600 47.89 69.77 33.32 753 000 34.23 49.87 30.79
Tenant’s distribution boards       Item @ £45 000 Electrical installation costs include the additional costs of supplies to fan-coil units for electric re-heat. Overall costs reduced as a result of the following design changes: use of flexible wiring systems to lighting in office areas; specification of armoured cable instead of cable and conduit where required; specification of economic luminaires to office areas; reduction of lighting load to 9 W/m2; rationalisation of lighting control specification.      
Small power installation to office areas; plug-in busbar and floor boxes       14 300 m² @ £18        
Small power to tenant’s ancillary areas       800 m² @ £12        
Power supply to fan-coil units       Item @ £55 000        
Lighting: switchgear and wiring to tenant’s areas       15 100 m² @ £10        
Lighting: luminaires and lamps to office areas       14 300 m² @ £25        
Lighting: luminaires and lamps to ancillary areas       800 m² @ £15        
Extra for emergency lighting installation; inverter packs and self-contained units       15 100 m² @ £3        
Lighting control system       15 100 m² @ £8        
Protective installations 234 100 10.64 15.50 7.40 234 000 10.64 15.50 9.57
Earthing and bonding to tenant’s areas       15 100 m² @ £0.50 Revised costs based on the simplification of the installation.      
Sprinkler installation (OH3); extension of sprinkler network into tenant’s areas; concealed heads       15 100 m² @ £15        
Communications installations 173 700 7.90 11.50 5.50 102 000 4.64 6.75 4.17
Fire alarm; detectors and secondary distribution to tenant’s areas       15 100 m² @ £11.50 Revised costs based on the specification of a fire alarm system with single stage/two stage evacuation programmes only, with no voice PA-based phased evacuation function.      
Special installations 185 200 8.42 12.26 5.86 149 000 6.77 9.87 6.09
Building management system/controls installation; controls to fan-coil units in office areas       15 100 m² @ £12 Reduced costs achieved by simplifying the specification of the building management system; including a reduction of the number of control points.      
BMS/controls to ancillary areas       Item @ £4000        
Builders work in connection 122 000 5.55 8.08 3.86 71 000 3.23 4.70 2.90
Forming holes, chases and so on; Allow 4%       Item @ £122 000 Reduced costs as a result of simplified category A fit-out installation.      
Category A fit-out total 3 161 400 143.71 209.35 100.00 2 446 000 111.19 161.99 100.00