Western Power Distribution Depot Achieving the Highest Rated BREEAM Score in the World

Western Power Distribution’s new 650m2 depot in Spilsby, Lincolnshire, recently achieved a BREEAM Outstanding rating of 100.5% at design stage under the BREEAM New Construction 2011: Simple Building’s scheme, making it the highest scoring BREEAM project in the world to date, with an anticipated 101.9% post-completion score.

Speller Metcalfe is an approved contractor for Western Power Distribution and this is the tenth project in a series of mainly fast-track, BREEAM projects won. As such, lessons learnt have been consistently reviewed to fine tune the design and construction approach to deliver excellent quality and environmental performance at best value.

There has been a range of elements that has led the project team to achieving such an unprecedented score, no less complicated than interpreting the BREEAM guidelines and responding accordingly wherever possible – although achieving this is not always a simple task.

Working to BIM

The designers on the project – B3 Architects, Nolan Associates and Halligan Associates developed plans for the depot using a data rich 3D model, which has led to considerable time savings (estimated 40%) in getting the project to planning versus traditional methods.

Through standardised specification developed on approaching 40 depot new builds and refurbishments this has led to a finely honed design process that provides access to a library of existing Western Power Distribution specific BIM component families and design base.

Nolan Associates used ACO Q max drainage system and large attenuation tanks to meet the requirements for SUDs drainage.

Energy Use & Zero Carbon

During design development, it became apparent that zero carbon energy performance could be achieved without exceeding budget, which was achieved through:

• A fabric first approach – this ensured excellent U value performance while delivering an airtight structure and enhanced energy performance;
• Thermal Modelling identified thermal comfort and building regulation compliance could be achieved through natural ventilation – consequently the MEP systems were simplified and mechanical ventilation and comfort cooling removed, reducing energy demand;
• It was identified that the rainwater harvesting system provided poor value for money as it only served one female / one male toilet area.  Capital freed was shifted to invest in photovoltaic installations which, along with the energy efficient design, resulted in a net zero carbon performance rating.
• 15/15 BREEAM credits were achieved under the Ene-1 Energy assessment with a further two innovation credits achieved for energy performance, resulting in a 106% improvement beyond the compliance requirements of Building Regulations Part L2a (2010).

The depot maximises use of renewable energy and energy efficient technologies in its design and operation. Use of refrigerants is limited with only a small, efficient system provided for the IT server room, and space heating / hot water provided by a high efficiency gas boiler with NOx emissions <39mg/kWh at 0% O2.

A water leak detection system is capable of identifying major leaks alongside a 55% improvement beyond performance for sanitary fittings achieved through specification of water efficient taps, WCs, urinals and showers. Unnecessary water wastage is prevented by using solenoid valves in each toilet block – restricting the water flow when unoccupied.

At least 80% of materials were sourced from suppliers with ISO14001 or BES6001 certification including the triple glazed windows and doors. All timber was sourced in accordance with the UK Government’s Timber Procurement Policy.

Biodiversity Protection & Enhancement

The existing site comprised agricultural land on the fringes of an existing industrial estate. The presence of an existing hedgerow presented a problem due to the summer construction start in the middle of bird nesting season. Working with a local ecologist the team removed part of the hedgerow with the remaining hedge left in situ and protected until the end of the season. Other protection measures included crawling boards in excavations to allow escape for mammals and litter picks of public footpaths around the site perimeter.

Overall, the landscaping scheme enhanced biodiversity on site compared with the ecological value prior to development, which included extensive planting of native plant species and installation of bat and bird boxes to create new habitats.

Delivering a ‘BREEAM Outstanding’ Building and Transferrable Sustainability

Achieving BREEAM Outstanding to demonstrate environmental excellence was a key driver for Western Power Distribution. To reach over 100% may seem impossible, but working alongside BREEAM Assessor Greenbuild Consult (acting as BREEAM AP) the contractor Speller Metcalfe were able to devise a detailed BREEAM action plan from an early RIBA stage, which targeted the extra innovation credits available and tipped our score over the 100% mark, including:

• Site Waste Management;
• Sustainable sourcing of materials;
• Energy Performance;
• Considerate Constructors –achieving 41/50 and a Bronze award at the National CCS Awards in 2014.

The value of WPD Spilsby to the wider UK construction industry is not as a multi-million pound architectural exemplar building loaded with green bling; it is as an example of how zero carbon energy performance can be achieved without exorbitant cost. Through a fabric first approach, emphasis on sensible low energy mechanical & electrical services and natural ventilation, BREEAM Outstanding has been achieved at a cost of £1,074/m2. 

We believe such affordable performance is what the UK desperately needs if we are to transform our building stock to meet the stringent Government carbon reduction targets, move away from reliance on high cost forms of energy and deliver construction methods accessible to the majority of the UK construction industry – SME’s.- 

Adrian Speller, Environmental Manager, Speller Metcalfe