Rainwater harvesting for DEFRA

Lion House is an ultra low-emissions office building, designed and built for the Department of Environment, Food and Rural Affairs (Defra), in Alnwick, Northumberland.

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 low-water use fittings and rainwater harvesting systems and the project’s M&E contractors Haden Young approached Kingspan Water, to design a suitable solution for the building.

The agreed system comprises of a pre-tank filtration system, a 12,000 litre underground storage tank, 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 to come from the rainwater harvesting system.

Gerry Quinn, product manager for Kingspan Water says:  “Reusing rainwater presents savings not just for the environment, but also in terms of reduced water rates.   At todays 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.”

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