Rainwater harvesting Case Study: National Centre for Autism Education

Freerain has recently supplied a rainwater havesting system for installation by Working Environments Ltd (Mechanical & Electrical contractor). The National Centre Centre for Autism Education has been built for the Treehouse Trust.

Source: Treehouse Trust Website, accessed 15 Oct 2008.

Sustainability
The building has been designed to be a low energy and low carbon building. The building is predicted to use 67% less energy than the energy benchmarks set out in the Greater London Authority's guidance for planners. 10% of the energy will be derived from renewable energy sources (ground coupled air pipes).

TreeHouse’s ‘Green Features’ include:

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  The roof will be planted with environmentally friendly sedum, creating a habitat for native flora and fauna; softening the visual impact of the building; and providing insulation to reduce the need for additional heating.
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  Rooflights on the first floor will ensure maximum daylight levels. Light shafts will provide daylight from the roof down to the ground floor classrooms to minimise the amount of artificial light needed.
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  Artificial lighting will be controlled by photocells linked to dimmers to minimise the artificial lighting load.
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  Energy efficient boilers will minimise the gas load for heating and hot water. The efficient fabric, form and air tightness of the building means that the heating load is low.
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  Rainwater recycling system will supply the WC flushes, reducing energy used in treating and supplying water to the building and treating surface water drained from the building.
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  High performance glazing will minimise solar transmission in summer and heat loss in winter, while still maintaining high light transmission to retain daylight levels.
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  A ground coupled air system will use the thermal mass of the ground as a heat source in winter (warming the incoming air) and as a heatsink in summer to cool the incoming air. This will result in a carbon saving of 10% or 1056kg/year.

The rainwater system supplied by Freerain included:

• 51,000L underground storage tank (including 27,000L of attenuation volume)
• 4no. Hydro-filters, these are a relatively new type of filter, originally designed for metal reduction from road run-off pollutants.
• Header tank type control system
• Ultra-violet sterilisation system
• Various pumping controls
• LED rainwater monitoring panel

The combination storage tank has allowed the surface water discharge to be controlled, but also cost savings on the total installation.