Waitrose’s landmark new National Distribution Centre in Milton Keynes has achieved an air permeability figure of 0.51m3/hr/m2 at 50Pa; the lowest for any building of its type.
The figure is one sixth of the Part L minimum requirement of 3.0m3/hr/m2, and almost half the value achieved for a similar project recently constructed using a built-up system.
The improved energy efficiency that results from this achievement is expected to save Waitrose £7,400 per year in energy costs, and reduce CO2 emissions by 39,000kg annually. This means savings of £222,000 and well over 1,000,000kg of CO2 emissions over the lifetime of the building.
The new distribution centre is spread over 45 acres at IDI Gazeley’s Magna Park development. High air permeability is usually a big challenge in such large buildings, particularly given the need to keep different temperature controlled areas at set temperatures. Loss of heat from main buildings, or chilled air from cold stores, results in higher running costs and less environmentally-friendly operations. Recognising this, Waitrose and IDI Gazeley specified an air permeability target of 1.0m3/hr/m2.
In order to meet this target, installer FK Group convened a supply chain team including representatives from Kingspan Insulated Panels; whose products are used extensively in the new building. The team aimed to develop an improvement on the existing standard panel fixing method used in buildings of this type.
Following extensive testing, the end laps between the roof panels were identified as a potential area for further work to improve air tightness. Recognising the importance of a holistic approach to ensure optimum efficiency, the team made a series of design and specification adjustments to improve the end lap details.
The eventual solution involved adjusting the purlin widths, the number and position of fixings per panel, the position of the lap tail, the use of a saddle washer at the 4-way lap, and the development of a bespoke mastic sealant.
“The end lap fixing detail produced for the new Waitrose facility at Magna Park is a real leap forward in the construction of this type of building,” commented FK Group Research, Development & Pre-construction Manager Chris Burgess. “We are constantly looking to improve the quality of our products and processes and it’s an approach that is greatly appreciated by clients, especially when we can produce results like this for them.”
“The result of this unique collaboration is clear; lower energy costs for Waitrose, a better building for IDI Gazeley, a reduced impact on the environment, and a first for the industry” explained Chris Wallis, Business Development Manager at Kingspan Insulated Panels. “This just goes to show the efficacy of insulated panel systems, which can achieve unparalleled performance compared with old-fashioned, built-up systems technology.”
The distribution centre is due to open in summer 2015, when it will begin handling the 25,000 product lines needed for Waitrose’s stores and online operations. It is expected to achieve a BREEAM ‘Excellent’ rating once assessed. McLaren Construction is the main contractor on the project.
Picture: FK Group.
