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Revisions to standard U-values of construction elements
Construction element U-values 1995
Revision (W/m2°C)		 U-values 2001
Revision (W/m2°C)
Pitched roof 0.25 0.16-0.20
Flat roof 0.25* 0.25
Walls, including basement walls 0.45 0.35
Floors, including ground floors and basement floors 0.45 0.25
Semi-exposed walls and floors 0.60 n/a
Windows, roof windows and doors (metal frames) 3.30 2.20
Windows, roof windows and personal doors (timber or PVCu frames) 3.30 2.00
Rooflights 3.30 2.20
Vehicle access and similar large doors 0.70 0.70
Source: Approved Document Part L (1995) and Approved Document L2
*0.45 if there is no loft space
Business park scheme
Base scheme compliant with Approved Document Part L (1995)
Element cost (£) cost/m2 gfa (£) % of total cost
Substructure 258,600 71.24 8.97
Pad and strip foundations, 150 mm thick suspended ground slab, below slab drainage, excavation, site preparation 2100 m2 @ £106    
Masonry wall construction below DPC; DPC; insulation 150 m2 @ £240    
Frame and upper floors 275,200 75.81 9.55
300 mm thick, insitu concrete flat slab, insitu concrete columns and shear walls 1900 m2 @ £112    
Structural steel framing 48 t @ £1300    
Roof 310,800 85.62 10.78
Pitched roof; roof trusses; felt; battens; accessories 1745 m2 @ £95    
Sarnafil to flat roof; plywood decking; insulation, vapour barrier, accessories 890 m2 @ £100    
Allowance for fascia boards, soffit cladding etc item @ £56,000    
Stairs 56,000 15.43 1.94
Mild steel main staircase with steel/timber handrails, external escape stairs item @ £56,000    
External walls, windows and doors 475,800 131.07 16.51
Cavity wall construction; facing brick and blockwork 920 m2 @ £150    
Miscellaneous works; additional dampproofing, blockwork plant enclosures item @ £22,500    
Punchhole windows, entrance screen, double door sets; sealed double-glazed units 855 m2@ £310    
Insulated louvres to plant rooms 335 m2 @ £150    
Internal partitions 80,900 22.29 2.81
Blockwork to cores 736 m2 @ £42    
Glazed partitions, WC cubicles and panelling item @ £50,000    
Internal doors 41,800 11.52 1.45
Veneered doors and frames to office areas and riser cupboards, glazed doors (average rate) 44 @ £950    
Wall finishes 60,300 16.61 2.09
Wallboard, decorations 2080 m2 @ £29    
Floor finishes 199,900 55.07 6.94
Raised floors, carpets, skirtings; to office areas 3350 m2 @ £47    
Floor finishes to common areas; tiles, carpets, screeds, skirtings item @ £42,400    
Ceiling finishes 78,700 21.68 2.73
Metal and plasterboard suspended ceilings; paint finishes 3350 m2 @ £20    
Ceiling finishes to common areas; suspended ceilings and painted plasteboard item @ £11,700    
Furniture and fittings 19,300 5.32 0.67
Vanitory units, mirrors, window boards, signage item @ £19,300    
Sanitary fittings 10,500 2.89 0.36
Allowance for sanitary installation item @ £10,500    
Disposal installations 23,000 6.34 0.80
Rainwater and soil and waste drainage item @ £23,000    
Water installations 26,800 7.38 0.93
Hot and cold water installation item @ £26,800    
Heating, air treatment and ventilation 231,400 63.75 8.03
Heat source and LPHW installation in plant rooms item @ £87,600    
LPHW distribution on office floors; insulation item @ £111,000    
Miscellaneous local space heating and ventilation installations item @ £32,800    
Electrical installations 209,600 57.74 7.27
Allowance for LV supply, LV switchpanel and sub-mains distribution item @ £24,600    
Lighting and small power installation 3630 m2 @ £50    
Miscellaneous electrical installations item @ £3500    
Lift installations 30,000 8.26 1.04
Lifts, 1 passenger lift item @ £30,000    
Protective installations 2,300 0.63 0.08
Earthing and bonding item @ £2300    
Communications installations 43,200 11.90 1.50
Communication installations generally; fire detection and alarm 3600 m2 @ £12    
Builders’ work in connection 29,000 7.99 1.01
Allowance for builders' work item @ £29,000    
Preliminaries and contingencies 419,000 115.43 14.54
Contractor's overheads, site establishment and site supervision; allow 12% item @ £296,000    
Contingency sum; allow 5% item @ £123,000    
Construction cost – building only £2,882,100 £793.97 100
 
City office scheme
Base scheme compliant with Approved Document Part L (1995)
Element cost (£) cost/m2 gfa (£) % of total cost
Substructure 4,500,000 137.20 7.72
Bored insitu piling; reinforced insitu concete wall and slab construction to two level basement; excavation 2500 m2 @ £1800    
Frame 3,480,000 106.10 5.97
Structural steel framing; board fire protection 2320 t @ £1500    
Upper floors 1,334,800 40.70 2.29
Composite floor slabs; 130 mm thick lightweight insitu concrete on metal decking 28,400 m2 @ £47    
Roof 798,800 24.35 1.37
Double-glazed utitised roof glazing 110 m2 @ £800    
Composite roof slabs; 130 mm thick lightweight insitu concrete on metal decking; two layer felt roofing 2250 m2 @ £160    
Reinforced concrete roof slabs at ground floor level to basements; smoke vents 520 m2 @ £290    
Plant bases, platforms, access ladders and balustrading item m2 @ £200,000    
Stairs 300,000 9.15 0.51
Precast concrete staircases, stainless steel balustrading and handrails 60 @ £5000    
External walls, windows and doors 10,879,600 331.70 18.66
Double glazed curtain walling; full-height glazing, aluminium framing at 1.5 m centres; external doors 12,500 m2 @ £710    
Aluminium metal panel soffit 260 m2 @ £420    
Insulated louvres to plant rooms 720 m2 @ £480    
Open louvre screens to roof level plant areas 1060 m2 @ £330    
Allowance for doors, canopies, stone plinths and skirtings, colunm casings, ventilator grilles, access doors and ladders, security grilles item @ £1,200,000    
Internal partitions 1,952,500 59.53 3.35
Basement blockwork, upper floor dry-lined partitions, glazed screens to ground floor 27,500 m2 @ £71    
Internal doors 931,000 28.38 1.60
Steel and veneered doors and frames to plant rooms and office areas; various fire ratings (average rate) 490 @ £1900    
Wall finishes 620,000 18.90 1.06
Glazed wall panelling, panelling and tiling to WCs, paint finishes 15,500 m2 @ £40    
Floor finishes 1,694,800 51.67 2.91
Raised floors to office areas 23,800 m2 @ £46    
Screeds; natural stone floor tiling; ceramic floor tiling; plant room finishes; paint finishes; generally item @ £600,000    
Ceiling finishes 1,298,600 39.59 2.23
Metal suspended ceilings; to office areas 23,800 m2 @ £47    
Plasterboard suspended ceilings; paint finishes item @ £180,000    
Furniture and fittings 1,500,000 45.73 2.57
Vanitory units, cubicle partitions, blinds, mirrors and general fittings item @ £1,500,000    
Sanitary fittings 120,000 3.66 0.20
Allowance for sanitary installation item @ £120,000    
Disposal installations 340,000 10.37 0.58
Rainwater, soil and waste and condensate drainage Item @ £340,000    
Water installations 190,000 5.79 0.33
Hot and cold water installation Item @ £190,000    
Heating, air treatment and ventilation 7,578,000 231.04 13.00
Gas installation item @ £40,000    
Heat source and LTHW installation in plant rooms item @ £380,000    
Chilled water and condensor water installations item @ £1,620,000    
Air handling plant item @ £360,000    
Supply and extract ductwork item @ £260,000    
Pipework and ductwork insulation generally item @ £590,000    
Fan coil units, on-floor LTHW and chilled water distribution pipework, insulation, supply and extract ductwork 32,800 m2 @ £110    
Miscellaneous local space heating and cooling installations item @ £220,000    
Miscellaneous local ventilation installations item @ £500,000    
Electrical installations 3,411,200 104.00 5.85
Allowance for HV switchgear, transformers and sub-mains distribution item @ £740,000    
Lighting installation 32,800 m2 @ £63    
Small power installation 32,800 m2 @ £16    
Miscellaneous electrical installations item @ £80,000    
Lift installations 3,030,000 92.38 5.20
Lifts, 8 passenger lifts, 2 passenger/firefighting lifts, 1 goods lift item @ £3,030,000    
Protective installations 984,000 30.00 1.69
Protective installations generally; lightning protection, sprinkler installations, dry risers and hose reels 32,800 m2 @ £30    
Communications installations 754,400 23.00 1.29
Communication installations generally; fire detection and alarm, telecommunications, CCTV and access control 32,800 m2 @ £23    
Special installations 1,964,000 59.88 3.37
ºÃÉ«ÏÈÉúTV management system 32,800 m2 @ £30    
Allowance for window and atrium cleaning systems, standby generation item @ £980,000    
Builders’ work in connection 920,000 28.05 1.58
Allowance for builders' work item @ £920,000    
Preliminaries and contingencies 9,716,000 296.22 16.67
Contractor's overheads, site establishment and site supervision; allow 15% item @ £7,287,000    
Contingency sum; allow 5% item @ £2,429,000    
Construction cost – building only £58,297,700 £1,777.39 100
 
Business Park scheme
Enhancements to scheme to comply with Approved Document L2
Option 1 – high performance glass
Element cost (£) cost/m2 gfa (£)
Construction cost of base scheme £2,882,100 £793.97
Substructure 7,200 1.98
Extra for: enhanced insulation to edges of ground floor slab to meet new U-values; 50 mm thick 240 m @ £30  
Roof 38,500 10.61
Extra for; additional insulation to pitched roof; between and across rafters; 150 mm thick 1745 m 2 @ £18  
Extra for; additional insulation to flat roof; 150 mm thick 890 m 2 @ £8  
External walls, windows and doors 45,300 12.48
Extra for; enhanced insulation to cavity wall construction; 150 mm thick; including works below DPC 1070 m 2 @ £1  
Extra over for high performance glazing to windows and doors; clear super neutral glass to outer pane 855 m 2 @ £40  
Extra for; enhanced insulation to plant room louvre panels and cladding; (encased insulation, overall thickness 130 mm) 335 m 2 @ £30  
Furniture and fittings 15,400 4.24
Window blinds 855 m2 @ £18  
Heating, air treatment and ventilation -2600 -0.72
Saving for; reduced boiler capacity due to improved thermal performance of building fabric; reduction of 15 kW; reduction related to perimeter heat losses only item @ -£4600  
Extra for; allowance for variable speed drives to boiler pumps item @ £2000  
Special installations 5000 1.38
Extra for; allowance for energy metering to main plant and Builders’ work in connection 400 0.11
Extra over costs of additional builders’ work item @ £400  
Preliminaries and contingencies 23,600 6.50
Contractor’s overheads, site establishment and supervision; allow 12% item @ £13,100  
Allowance for provision of log books and enhanced manuals item @ £5000  
Contingency sum; allow 5% item @ £5500  
Construction cost – building only including costs of Part L compliance £3,014,900 £830.55
Extra over costs of Part L compliance £132,800 £36.58
Overall percentage increase 4.4%
 
City office scheme
Enhancements to scheme to comply with Approved Document L2
Option 1 – high performance glass
Element cost (£) cost/m2 gfa (£)
Construction cost of base scheme £58,297,700 £1,777.39
Roof 29,900 0.91
Extra over double-glazed roof glazing for improved thermal/solar performance; high performance glass; toughened and heat strengthened 110 m2 @ £70  
Extra for; enhanced insulation to roof slabs to meet new U-values (overall thickness 150 mm) 2770 m2 @ £8  
External walls, windows and doors 2,529,400 77.12
Extra over double glazed curtain walling; for improved thermal/solar performance; triple wall facade with interstitial blinds 12,500 m2 @ £200  
Extra over soffit panels and louvres for improved insulation to meet revised U-value (encased insulation, overall thickness 130 mm) 980 m2 @ £30  
Furniture and fittings -90,000 -2.74
Saving for; blinds now included in the triple facade system 5000 m2 @ £18  
Heating, air treatment and ventilation -97,000 -2.96
Extra for; high efficiency boiler plant; condensing boilers item @ £30,000  
Saving for; reduced boiler capacity and pipework sizes due to improved facade performance; reduction of 100 kW; reduction related to perimeter heat losses only item @ -£24,000  
Saving for; reduced chiller capacity and pipework sizes due to improved facade performance; reduction of 950 kW; reduction related to solar heat gains only item @ -£170,000  
Extra for; allowance for heat recovery installation to air handling plant item @ £12,000  
Extra for; allowance for 10% increase in ductwork cross section area (including insulation) item @ £35,000  
Extra for; allowance for variable speed drives to pumps and fans item @ £20,000  
Special installations 30,000 0.91
Extra for; allowance for enhanced BMS controls; additional programming item @ £10,000  
Extra for; allowance for additional metering to landlord's plant item @ £20,000  
Builders’ work in connection 6000 0.18
Extra over costs of additional builders’ work item @ £6000  
Preliminaries and contingencies 491,000 14.97
Contractor’s overheads, site establishment and supervision; allow 15% item @ £361,000  
Allowance for provision of log books and enhanced manuals item @ £10,000  
Contingency sum; allow 5% item @ £120,000  
Construction cost – building only, including costs of Part L compliance £61,197,000 £1865.78
Extra over costs of Part L Compliance £2,899,300 £88.39
Overall percentage increase 4.97%
Business Park scheme
Enhancements to scheme to comply with Approved Document L2
Option 2 – low-emissivity glass
Element cost (£) cost/m2 gfa (£)
Construction cost of base scheme £2,882,100 £793.97
Substructure 7200 1.98
Extra for: enhanced insulation to edges of ground floor slab to meet new U-values; 50 mm thick 240 m @ £30  
Roof 38,500 10.61
Extra for; additional insulation to pitched roof; between and across rafters; 150 mm thick 1745 m2 @ £18  
Extra for; additional insulation to flat roof; 150 mm thick 890 m2 @ £8  
External walls, windows and doors 21,400 5.90
Extra for; enhanced insulation to cavity wall construction; 150 mm thick; including works below DPC 1070 m2 @ £1  
Extra over for low-e glazing to windows and doors 855 m2 @ £12  
Extra for; enhanced insulation to plant room louvre panels and cladding; (encased insulation, overall thickness 130 mm) 335 m2 @ £30  
Furniture and fittings 15,400 4.24
Window blinds 855 m2 @ £18  
Heating, air treatment and ventilation 1600 0.44
Saving for; reduced boiler capacity due to improved thermal performance of building fabric; reduction of 15 kW; reduction related to perimeter heat losses only item @ £3600  
Extra for; allowance for variable speed drives to boiler pumps item @ £2000  
Special installations 5000 1.38
Extra for; allowance for energy metering to main plant and distribution boards item @ £5000  
Builders’ work in connection 400 0.11
Extra over costs of additional builders’ work item @ £400  
Preliminaries and contingencies 19,700 5.43
Contractor’s overheads, site establishment and site supervision; allow 12% item @ £10,400  
Allowance for provision of log books and enhanced manuals item @ £5000  
Contingency sum; allow 5% item @ £4300
Construction cost – building only, including costs of Part L compliance £2,988,100 £823.18
Extra over costs of Part L compliance £106,000 £29.21
Overall percentage increase 3.55%
City Office scheme
Enhancements to scheme to comply with Approved Document L2
Option 2 – double-glazed curtain walling with high performance glass and blinds
Element cost (£) cost/m2 gfa (£)
Construction cost of base scheme £58,297,700 £1,777.39
Roof 35,400 1.08
Extra over double glazed roof glazing for improved thermal/solar performance; high performance glass; toughened and heat strengthened 110 m2 @ £70  
Extra for; enhanced insulation to roof slabs to meet new U-values (overall thickness 150 mm) 2770 m2 @ £10  
External walls, windows and doors 654,400 19.95
Extra over double glazed curtain walling; for improved thermal/solar performance; high performance glass; clear super neutral to outer leaf 12,500 m2 @ £50  
Extra over soffit panels and louvres for improved insulation to meet revised U-value (encased insulation, overall thickness 130 mm) 980m2 @ £30  
Heating, air treatment and ventilation 68,000 (2.07)
Extra for; high efficiency boiler plant item @ £30,000  
Saving for; reduced boiler capacity and pipework sizes due to improved façade performance; reduction of 62 kW; reduction related to perimeter heat losses only item @ (£15,000)  
Saving for; reduced chiller capacity and pipework sizes due to improved façade performance; reduction of 840 kW; reduction related to solar heat gains only item @ (£150,000)  
Extra for; allowance for heat recovery installation to air handling plant item @ £12,000  
Extra for; allowance for 10% increase in ductwork cross section area (including insulation) item @ £35,000  
Extra for; allowance for variable speed drives to pumps and fans item @ £20,000  
Special installations 30,000 0.91
Extra for; allowance for enhanced BMS controls; additional programming item @ £10,000  
Extra for; allowance for additional metering to landlord's plant item @ £20,000  
Builders’ work in connection 6000 0.18
Extra over costs of additional builders’ work item @ £6000  
Preliminaries and contingencies 142,000 4.33
Contractor’s overheads, site establishment and site supervision; allow 15% item @ £99,000  
Allowance for provision of log books and enhanced manuals item @ £10,000  
Contingency sum; allow 5% item @ £33,000  
Construction cost – building only including costs of Part L compliance £59,097,500 £1801.77
Extra over costs of Part L compliance £799,800 £24.38
Overall percentage increase 1.37%