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The Glasgow Lighthouse has received funding for an initiative to transform its viewing gallery into a zero-energy space

The Lighthouse is the flagship project of the Glasgow 1999 celebrations. Designed in 1883 by Charles Rennie Mackintosh, the building was originally the office of The Herald newspaper and has been derelict for 20 years. It is now being transformed into an architecture and design centre by a project team which includes architect Page & Park, consulting services engineer Oscar Faber, Glasgow City Council, the Energy Design Advice Scheme and the Energy Systems Research Unit at the University of Strathclyde.

Funds for the £12.25 million conversion are being provided by the National Lottery, the Scottish Arts Council and other groups, with the City Council and the European Union providing funds for an initiative to turn the viewing gallery on the roof into a zero-energy space, able to produce its own heat and light all year round.

The University of Strathclyde used computer simulation to determine the performance of the initial design for the viewing gallery, and then to monitor the effect of various modifications. The initial design consisted of an insulated steel-clad facade, insulated lead-sheet roof, extensive double-glazing, and a slate-covered concrete floor slab with external insulation. Building services comprised embedded floor heating, halogen display lighting and natural ventilation from vented slot windows.

In the first test, the north and east-facing double-glazing was replaced with low-E coated triple glazing filled with argon (a poor heat conductor), with a centre pane U-value of 0.8W/m2K. South-facing porthole windows were fitted with liquid crystal panels which automatically darken in strong sunlight to prevent overheating, and prismatic glass was added to the north facade where it will prevent glare by redirecting sunlight on to ceilings. These measures resulted in a 58 per cent reduction in annual heating energy requirements, and a 31 per cent reduction for required energy overall. Secondly, sensors which automatically adjust internal lighting in response to changes in light levels outside were added to the model, along with a south-facing transparent insulated thermal mass wall which is able to meet heating requirements during the transitional seasons, reducing the need for auxiliary heating to winter.

When compared to the initial design, the advanced glazing, lighting controls, and transparent insulated facade produced a 45 per cent reduction in annual heating energy demand, a 59 per cent reduction in lighting energy demand, and a 51 per cent reduction in the overall energy demand. Finally, the underfloor heating system was replaced with a fast-response convective heating system, and the lamps were replaced with high-efficiency luminaires. These measures resulted in a 58 per cent reduction in annual heating energy demand, a 67 per cent reduction in heating plant capacity, an 80 per cent reduction in lighting energy demand, and a 68 per cent reduction in overall energy demand when compared to the original design.

Cost constraints meant that not all of the measures proposed by the investigations have been implemented. Argon-filled double-glazing is being installed instead of the recommended triple-glazing, and plans to use automatically darkening glass have been abandoned.

In addition to the energy demand-reduction techniques outlined above, the observation gallery uses active renewable energy systems. A photovoltaic system is being incorporated within the south-facing facade, while ducted wind turbines will be mounted in the south and west-facing edges of the roof (south-westerlies are the predominant wind direction in Glasgow). The beauty of this combination is that ducted wind turbines are most productive during winter when photovoltaic components contribute little, whereas photovoltaic components are most productive during the summer when winds are light.

Together, the passive and active renewable energy systems are able to meet the demands of the space during spring, summer and autumn. Active renewable energy systems will meet much of the energy demand in winter, but an electrical storage system will be necessary to compensate for the fact that much of the supply is available outside the times that the building is in use.

During its first year of occupation, the building will be closely monitored to establish the performance and durability of the renewable energy systems. Research results will be published on the web.

The Lighthouse is the first Scottish building to sign up for ScottishPower's Green Energy Tariff, whereby ScottishPower will match customer contributions of 4p a day for the average domestic electricity account, and 28p a day for businesses, in order to invest in wind and hydro-generating plant. Mackintosh himself would doubtless have approved: he was very careful about the use of heating and light, and pioneered the use of air ducts to carry heat round his buildings.

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