Lion House is an ultra low-emissions office building, designed and built for the Department of Environment, Food and Rural Affairs (DEFRA) in Alnwick. From the outset, the aim was to construct a building with the highest possible BREEAM rating. That included incorporating low-energy technologies, responsibly sourced materials and reduced carbon emissions.

There was also the aim of minimising mains water consumption through water-saving fittings and rainwater harvesting systems. The project's M&E contractors, Haden Young, approached one of the UK's leading suppliers of rainwater harvesting equipment, Kingspan Environmental, to design a suitable solution for the building.

The Kingspan Environmental team worked closely with Haden Young to configure its Envireau equipment to meet the water consumption requirements for toilet flushing for Lion Houses 100 employees. The agreed system comprises a pre-tank filtration system, a 12,000 litre underground storage tank, and an electronic control system and pump. The pump in the main holding tank delivers the water to a high-level header tank in the building, from where the water will gravity-flow to the serviced appliances.

The team calculated that the annual water consumption at Lion House will be around 469m3. Given the roof area of the new building, and the annual rainfall statistics for the region, it is estimated that the annual water harvest will be around 563m3. In theory, therefore, all of the annual toilet flushing water is expected come from the rainwater harvesting system.

Gerry Quinn, Product Manager for KingspanWater says: "Reusing rainwater presents savings not just for the environment, but also in terms of reduced water rates. At today's water cost, we expect to see Lion House saving in the region of £800 per annum, so we would anticipate payback on capital investment in around four to five years."

The project won the 2008 BREEAM Office Category for Excellent Environmental Performance.

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