York Eco Depot

Date: 2007

Location: York

Business benefits:

Demonstration of our business as a market leader in sustainable construction

Raising awareness of our ability to provide sustainable solutions to meet our Client’s aspirations

Promotion of environmental awareness to the local community and school children, the eco office provides an interpretation room dedicated to learning and education for all.

Key facts:

Largest timber frame straw bale clad building in Europe (November 2007)

76% reduction of energy use compared to a traditional air-conditioned office

Low maintenance costs: Cost of energy for normal office with air-conditioning is approx £40 per sq. m and for the Eco depot is only £5 per sq. m

52Kw photovoltaic array

Grey-water recycling system for vehicle wash

If you were sent looking for a new sustainable design, award-winning office building, you could be forgiven if you started your search in the private sector looking for a showpiece building on a prominent site. You may then be surprised to find that a building fitting this brief can be found on an unremarkable industrial area just outside the centre of York, providing a depot for the City of York Council’s environmental and waste services.

Located on a site away from public view, this building was designed for functionality and efficiency from a collaborative relationship between City of York Council, White Design architectural practice, Yorkshire Forward and Carillion.

The most unique aspect of the development is that the main Eco-Depot building is currently the largest timber frame straw-clad building in Europe. This innovative use of materials means that there is no air-conditioning unit; the building is kept at a comfortable temperature using passive bio-climatic design, under-floor heating and excellent insulation from the straw walls. An intelligent Building Management System also controls the opening and closing of windows and sun shades using weather data and outdoor sensors. Large open rooms allow for natural ventilation and high ceilings give soft acoustics indoors. Full length windows and skylights reduce the need for electric lighting and create an open working environment.

When Carillion secured the contract for a new depot, the original request was for standard design with no sustainability requirements. In 2005 however, with additional funding granted from Yorkshire Forward, Kristina Peat, City of York Council Sustainability Officer redefined the brief to require an eco building and Carillion stepped up to the challenge. Whilst the client was clear on their overall intention there were only outline specifications written into the brief, which included low carbon footprint in construction and operation, low energy and water use and local sourcing where practical. Therefore, based on a positive client partnership that shared risk and reward, it was left to the design team to interpret and deliver the vision within the £8million budget.

During the design process Carillion visited the previous depot building to study and account the working day of York Council’s Neighbourhood Services employees. The building design was then developed around the functionality of the teams and employee’s work patterns.

The choice of building materials is one of the most distinctive aspects of this development. AgriFibre provided the straw bales Modcell units, using locally sourced straw and timber off-cuts with local labour found through contact with a local agricultural college. The straw units are then covered with a lime render and plaster from Lime Technology which not only offers a renewable and low carbon sourced materials, but also great thermal massing properties to help with the heating and cooling of the building. The insulation properties of the straw are three times better than those required by Building Regulations and will provide a 76% reduction in energy use compared to a traditionally built, air-conditioned office of the same volume.

The straw units were manufactured specifically to fit the design and were fixed as complete wall sections against full-length windows, making the construction process far quicker and cheaper than a ‘window to cladding’ method and with very little waste created. The units are modular and could therefore be erected and replaced with relative ease. The straw is also pre-compressed and framed in a unique solid timber enclosure to reduce settlement and provide retention against fire risk by removing air from the material. The lime render also gives further protection for the exterior walls and eliminates the need for any further building materials.

The timber frame of the building used FSC certified timber and a two-storey curved cedar wall provides an impressive feature in the main meeting rooms. Across the rest of the site, the vehicle storage sheds have a grey-water system collecting water from the large roof, which is used for washing the maintenance vehicles. This is a vast improvement from the previous system where treated drinking water was used to wash the trucks at a cost of about £25,000 a year. Photovoltaic panels have been positioned on the roof of the canteen building to collect solar energy and provide hot water for the showers and canteen. The site also has planning permission for a 15kW wind turbine, which is to be erected once funding is secured.

The Eco-depot was built within a year and staff moved into the building in November 2006. The first year of occupation has gone smoothly in terms of building management with only a few adjustments required. By early 2008, data should be available to carry out a full comparison between the performance of the old and new buildings. Early indications however, suggest that whilst the PV’s were intended to provide 12% of energy requirements, a mild winter meant that approximately 40% of energy was provided by solar power over the first year. The water recycling system in particular should provide at least a 50% reduction in the use of treated water.

The success of the building has bought a new learning opportunity to York. School children often visit the site and use the large interpretation room where they can see the straw bale components and learn about the impacts of material usage and waste.

This development, by providing a physical example of sustainability, has been a great learning opportunity for City of York Council. The council is now planning to develop a new Head Office building for 1,300 staff in the centre of York, which will also utilise sustainable design and construction and request BREEAM Excellent and 20% renewable energy. Kristina Peat explained “the experience of the Eco-Depot has illustrated to York Council the capabilities and benefits of sustainable construction. By proving the success of these practices from a real building, we can now apply this on a much larger scale.”

For Carillion, this project provides a number of company ‘firsts’ with new construction materials, new building methods, new suppliers and new client requirements. However, the results speak for themselves and in this case, Carillion delivered a truly exemplary building to satisfied customers. Contracts Manager Brian Dunn, commented “whilst there were many new techniques and materials used during the build, the benefits both for the client and our own knowledge base far out-weighs any complications and I would certainly do it all again”.

The City of York Eco Depot has won many awards including:

Carillion Sustainability Project of the Year 2007

Institution of Civil Engineers (Yorkshire & Humberside). ‘Highly Commended Award’

Green Apple Awards – Gold Award in its category for the built environment and architectural heritage scheme as run by the Green Organisation

Considerate Constructors 2007 National Award Winner, Bronze category