Careful teamwork integrating many small solutions built up a big sustainable gain 'Acareful team approach, which involved working through options and making the right decisions early on, has been the key to achieving a sustainable construction solution for the new pier five at Heathrow's Terminal 3, ' says Gary Callaghan, from E&M consultant Roger Preston & Partners, part of the BAA design and construction project team.
Integrating many smaller design elements rather than 'rocket science' engineering, has nevertheless given pier five an annual CO 2emission performance of around 95kg/m 2/ year. 'That is better than the previous BAA 'best case' of Satellite Three at Stansted airport, ' says Callaghan.
The £34M extension at Heathrow Terminal 3 incorporates a range of energy saving and environmental measures, from daylight controlled lighting, energy efficient glazing and displacement ventilation to energy recovery systems. But thorough assessment of costs and life returns ruled out other 'conventional' sustainability solutions such as solar panels for the cladding, and rainwater harvesting.
The new pier allows direct internal passenger access to some of the international terminal's remote stands. It will also provide the first two gates able to handle the new giant-jumbo A380 planes when they come into service in 2006.
'As such, ' says Callaghan, 'BAA wanted to see a design with a 'wow' factor for the large number of passengers waiting in the departure and gate lounges.
'The design is for a 5.5m high departure lounge featuring large windows - the extension as a whole had to include at least 50% glazing - to take advantage of views of the new Terminal 5 and across the airport, ' he says.
With so much glass, the consequent heat gains are cut by low transmission glass passing 27% to 28% of radiant energy, use of brise soleils to cut peak sunlight and careful siting of the arrivals corridor to shade the main departure lounge.
The team also decided to go for the lower U-values in the new Building Regulations Part L, even though the planning application pre-dates them. 'In the end that perhaps proved helpful, ' says Callaghan.
Another problem with glazing is that bright daylight can accentuate shadow contrast. 'We incorporate rooflights to brighten areas and reduce artificial light needs, ' Callaghan says.
Where lighting is needed, its level is varied to balance the measured daylight brightness, saving energy.
Greater savings are achieved with the air conditioning. The team has opted for displacement ventilation, introducing air through floor level outlets.
'It forms a low level layer of cooler air which then rises around any heat source, ' says Callaghan 'that usually being a person.'
The system ties neatly with the use of the ground floor space for plant rooms and allows air to be introduced only a few degrees below ambient temperature at 19C, to achieve the 23C for room comfort. A full mixed-air system would mean cooling air to 12C and correspondingly more energy use.
'We can also use outside fresh air with little treatment for much of the year, ' says Callaghan.
Warmer air rising into the ceiling space can be 'left to look after itself', he adds, with less high level ducting making the work of the lighting and other team members easier.
Heat exchangers do, however, recover heat or lose it as appropriate for the time of year.
'We also looked at rainwater harvesting, ' says Callaghan, 'but the use of non-potable water is only possible in some of the toilet blocks and providing the infrastructure is expensive, so the payback time is several decades.'
A final sustainable concept, solar electricity, also just missed out, mainly because sight lines imposed on the building prevented the use of panels on enough of the facades to be economic.
Roger Preston & Partners
Buro Happold Structural Engineers