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Timber and PVCu windows
Softwood windows Ìý
Redwood double vacuum impregnated with an organic solvent preservative to British Wood Preserving and Dampproofing Association (BWPDA) schedule V1 or V2 after machining. Joints fully coated in weather- and boil-proof (WBP) quality adhesive or D4 adhesive to BS EN 204 so as to seal end grain. Timber quality at least Class J50 for frames, Class J40 for sashes, and Class J30 for beads. Capital cost £211/m2
Net present value for 60-year life £354/m2
Service life 35 years
Heartwood only of untreated softwood from a species designated as suitable without preservative treatment (SW) or suitable without preservation if covered (SWC) to BS EN 942, table NA1 – for example, Douglas fir or western red cedar. Joints fully coated in WBP quality adhesive or D4 adhesive to BS EN 204 so as to seal end grain. Capital cost £226/m2
Net present value for 60-year life £371/m2
Service life 35 years
Selected redwood double vacuum impregnated with an organic solvent preservative to BWPDA schedule V1 or V2 or selected whitewood or hemlock to V3 after machining. Joints fully coated in moisture-resistant (MR) quality adhesive or type D3 adhesive to BS EN 204 so as to seal end grain. Capital cost £206/m2
Net present value for 60-year life £372/m2
Service life 25 years
Selected redwood treated with a three-minute immersion in an organic solvent preservative after machining. Joints fully coated in MR quality adhesive or type D3 adhesive to BS EN 204 so as to seal end grain. Capital cost £198/m2
Net present value for 60-year life £389/m2
Service life 15 years
Redwood or whitewood untreated or whitewood or hemlock immersion treated. Joints fully coated in MR quality adhesive or type D3 adhesive to BS EN 204 so as to seal end grain. Capital cost £194/m2
Net present value for 60-year life £466/m2
Service life 10 years
PVCu windows Ìý
Third-party assessed window ranges; kitemarked to BS 7412 or BBA certified or London Housing Consortium arrangement U5. Plastic to BS 7413 (impact modified plastics) and construction to BS 7412. BBA-approved window systems supplied by BBA-approved manufacturers. Window hardware to be only as tested and approved by BBA or LHC or kitemarked to BS 7412.Capital cost £257/m2
Net present value for 60-year life £372/m2
Service life 40 years
White PVCu hollow profile, multi-chamber frames and sashes internally reinforced with as necessary with close-fitting stainless steel, aluminium or pre-galvanized – minimum 275 g/m² zinc both sides – steel sections. Plastic to BS 7413 (impact modified plastics) and construction to BS 7412. Capital cost £277/m2
Net present value for 60-year life £403/m2
Service life 35 years
Film coloured PVCu hollow profile, multi-chamber frames and sashes, internally reinforced as necessary with close-fitting stainless steel, aluminium or pre–galvanized – minimum 275g/m² zinc both sides – steel sections. Plastic to BS 7413 (impact modified plastics) and construction to BS 7412. Colour film to comply with BS 7722. Capital cost £252/m2
Net present value for 60-year life £404/m2
Service life 25 years