Prioritising design for climate change
Energy use in buildings accounts for over 40% of carbon emissions in Europe: to put this into context that’s more than all the forms of transport put together. Recent flooding in the UK and abroad has shown us the dangers of complacency when it comes to climate change, as extreme global weather over the past two years has fuelled speculation that global warming, due at least in part to carbon emissions, is beginning to destabilise the Earth's climate.
In response, the EU has committed itself to reducing CO2 emissions by 20 percent by 2020. Tougher targets have been put in place in the UK too; the 2006 amendment to 'Part F: Conservation of fuel and power of the Building Regulations' requires higher thermal standards in buildings, which will contribute to the reduction of greenhouse gases in line with the Government’s long-term target of a 60 percent decrease by 2050.
A whole building approach will reduce building emissions by up to 40 percent
The amended regulations require using a whole building approach to calculate energy efficiency, and will reduce carbon emissions from buildings by up to 40 percent. Also, for the first time, buildings over 1,000m2 undergoing major refurbishment will have to be upgraded to comply with energy performance requirements.
Energy-efficient building is of course key to cutting carbon emissions. Sustainable engineering is now firmly established as an integral process within the design, construction and operation of most new building developments. Incorporating the latest energy-saving building services technologies and recycling systems, companies like Buro Happold compete to set a new benchmark for environmental performance.
“Meeting sustainability targets is a key regulatory requirement, and is likely to become more significant in the future,” said Andrew Cripps, associate director at Buro Happold. “Engineers can play a vital role in enabling clients to procure buildings that are environmentally responsible. After analysing the environmental ‘behaviour’ of a structure, it is possible to evaluate the sustainability of the design choices using recognised rating systems such as BREEAM and LEED. Here at Buro Happold, we have a dedicated SAT (Sustainability and Alternative Technologies) team, who not only design sustainability in, but also carry out post-occupancy evaluations to ensure that subsequent energy use is efficient as possible.”
Practical, integrated solutions lead to great long-term cost savings
There are many practical, integrated building services solutions available now, creating a balanced and energy-efficient internal environment, and cutting emissions by up to 60% compared to standard regulations-compliant buildings. They also save money in the long term, with vastly reduced energy bills. At the biotechnology group Genzyme’s headquarters in Massachussetts (a 12-storey office development built by Buro Happold in 2004), energy use has been cut by 42% and water consumption by 34%, compared to a conventional building of its size.
Two recent Buro Happold building projects are exemplars of sustainable design, shining a light on the way forward. One is John Wheatley College in Glasgow, which is aiming for a BREEAM ‘Excellent’ rating, and the other is the ‘Three Gardens’ affordable housing development in Elmswell, Suffolk, itself aiming for an Eco-Homes ‘Excellent’ rating. They both do this by harnessing natural resources, setting the highest standards of thermal efficiency, and using innovative materials and building methods.
Harnessing natural resources
At John Wheatley College, a biomass boiler provides the thermal energy to meet the base load space heating and hot water demand. The boiler is fuelled by pellets, burning more cleanly than wood chips, and requiring fewer fuel deliveries and a smaller fuel store. Meanwhile, air source heat pumps provide thermal energy to supply space heating via an underfloor heating system.
Solar PV (photovoltaic) modules in the ETFE foil roof provide electricity to supplement the mains supply. Electricity supply switches seamlessly between mains electricity and that generated by the PV modules, depending on availability, and excess PV-generated electricity is exported.
Furthermore, solar panels meet the hot water demand through the summer months, extending the period when the biomass boiler is turned off, and rainwater is harvested for flushing toilets, significantly reducing the building’s reliance on mains water.
At other Buro Happold projects, such as Edinburgh’s Royal Botanic Gardens visitor centre which is currently under construction, wind-turbines are included to further harness natural resources.
Thermal efficiency, airtightness and ventilation
Heat management also plays a major role in energy reduction. At John Wheatley College natural ventilation has been adopted throughout, to provide fresh air ventilation and to cool the spaces passively. Extensive simulation and CFD modelling at the college demonstrated the performance of individual spaces and allowed fine-tuning of material selection and window opening. Meanwhile, at ‘Three Gardens’, whole house ventilation allows up to 80% heat recovery.
Exposed thermal mass will store heat from the sun in the winter and act as a heat sink for cooling in the summer. The benefits of thermal mass are often lost through excessive wall, ceiling and floor coverings, so at the college, exposed thermal mass was incorporated within the classroom wing. The thermal mass is charged at night, using night cooling techniques, allowing cooling to be available during the day.
Buildings with large expanses of glazing have different requirements to make best use of the sun’s power than do domestic living spaces. At the college, façade shading has been optimised where necessary to reduce glare and minimise cooling requirements; shades were carefully designed to deal with both summer and winter sun angles. By contrast at ‘Three Gardens’, the living spaces are staggered over a vertical section to maximise passive solar gain in winter; the building envelope and glazing ratios were modelled by Buro Happold to establish the optimum relationship between solar gain and daylight penetration.
Natural daylight is used in both schemes as much as possible, and at the college daylighting factors of over 5% in all areas of the building were achieved, with extensive use of rooflights.
In terms of airtightness, several simple steps help to prevent wastage. At ‘Three Gardens’ it was designed in, with care taken at all stages to avoid leakage through cracks and joints; joists penetrating external walls, timber floors and the junctions where stud walls meet the floors and ceilings.
Finally, there are numerous methods of encouraging the end users of a building to minimise energy use (which can be tweaked following a post-occupancy evaluation), and at the college the following building services systems are in place:
• Low energy artificial lighting.
• Speed controls on all pumps, fans and electrical motors.
• Central lighting controls complete with daylight linking and movement detection systems.
• Localised metering.
• A BMS control system, optimising the control and monitoring of the services equipment.
Innovative use of building materials
The building materials themselves can make a huge difference to the sustainability of a project, and Elmswell’s ‘Three Gardens’ affordable housing project is an outstanding example.
Deeply committed to sustainability from the outset, the development makes as much use of local materials as possible. The houses are timber-frame constructions, and the walls are made from ‘hemcrete’ sprayed onto the wooden formwork. ‘Hemcrete’ is a hemp-and-lime matrix which has excellent environmental and thermal properties. One of the region’s oldest crops, hemp has the ability to lock carbon into the very fabric of the building. This means that it is carbon-negative, as it absorbs more carbon while growing than is used in its subsequent manufacture – during which the captured carbon remains contained.
Furthermore, the insulation is made from local sheep’s wool, and the biomass boiler is fuelled by the area’s trove of woodchip. Local clays, earth and chalk have been used, maximising local character while minimising transportation needs; indeed, no steel and only minimal concrete have been used throughout the site.
Pre-fabrication is also used on many of Buro Happold’s projects, reducing energy consumption during construction, by allowing components to be assembled off site and delivered in modules.
“As pioneers in the design of low-energy, high performance buildings and systems, we fully support the high priority now given to sustainability and welcomes the challenges this presents,” said Rod Manson, Regional Director at Buro Happold. “I hope other consultancies will do likewise – we are moving in the right direction, but as a society we still have a way to go before all our buildings are as energy-efficient as possible. At Buro Happold we are aiming for each of our building projects to achieve a 30 percent reduction in carbon emissions against published benchmarking data. In the future, we will see this level of reduction increasing as building control standards and government initiatives drive the built environment to higher standards.”
