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Costs: alternative roofing systems

Davis Langdon provides supply-and-fix costs for alternative roofing products and systems that are now featuring on roofing schemes. The costs represent typical indicative rates for medium-sized projects in the outer London area in March 2005. It must be noted that, due to the nature of these products, the costs vary and costs should be sought from the specialist contractors

ROOFING SYSTEMS Ethyletetrafluoroethylene (ETFE) systems Known for its use on the Eden Project, ETFE is experiencing an increase in popularity and is viewed as a lightweight 'green' building material. ETFE with its low weight and ability to transmit light has begun to replace glass in atria and roof lights £/m 2l Material 250-350 l Structural steel frame 280-350 This includes for a three-layer system and all associated 'pillow' infl ation systems based on 30,000m² Solar photovoltaic (PV) systems Solar photovoltaic (PV) is the science of converting light energy into electricity. Solar modules, constructed by laminating electrically interconnected solar cells under glass, carry out the conversion. Solar cell and module technologies vary in cost and performance; the amount of energy that each produces being a function of the particular technology and the amount of light available £/m 2l Standard PV modules 700-800 l Bespoke PV modules 925-1,100 Cost based on the use of mono-crystalline modules. The bulk of the cost is the photovoltaic and the secondary support; the ancillary system equipment such as inverters and switchgear form 10-20 per cent, with labour costs at the same level Solar water heating Solar water-heating systems use solar collectors fitted on the roof and connected to a new special water cylinder. An electronic controller constantly compares the temperatures of the collectors and the water. When the collectors are hotter, the system's circulating pump is turned on and the water circulated in the same way as in a central-heating boiler. Designed to provide a contribution of 50-70 per cent of household annual water heating requirements £/m 2l Flat plate 475-725 l Evacuated tube collectors 600-850 Based on a typical roof collection area of 4 - 6m² for a medium-sized house.

Landscaped roof Vapour barrier, polyester-based elastomeric bitumen waterproofing and vapour equalisation layer, copper-lined bitumen membrane root barrier and waterproofing layer, separation and slip layers, protection layer, 50mm-thick drainage board, filter fleece, insulation, top soil and seed £/m 2l Intensive (high-maintenance, lawns, shrubs, etc) 130-160 l Extensive (low-maintenance shrubs, mulching, etc) 120 150 INCREASED DAYLIGHT OPTIONS Increased daylighting will reduce energy use and also provide a better environment. New polycarbonate skylights can be designed to use transparent insulation like twin-wall polycarbonate to allow light while maintaining low U-values Roof lights £/m 2l Individual rectangular polycarbonate roof lights to fl at or sloping roof 400-500 l Individual circular polycarbonate roof light hatches 1,050-1,200 The rates allow for opening gear, frame kerb and glazing Sun pipes £/m 2l Pitched roof (300-500mm diameter) 350-475 l Flat roof (300-395mm diameter) 300-420 l Extra - lead flashings 90-125 l Motorised light/sun damper 225-250 Sun-pipes rates allow for flashing plate, ceiling trims, adjustable connectors ENVIRONMENTAL BUFFERING The roof can assist by sheltering and providing a protective layer above the building for sun-shade purposes Brise-soleil £/m 2l Extruded aluminium blades, set horizontally on purpose-designed brackets, vertical support not included 150-250 l Western red cedar timber brise-soleil, vertical support not included 180-300

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