Look at the whole energy picture

With the Government currently considering a draft climate change bill to curb carbon dioxide emissions it appears global warming is finally being taken seriously. This is no surprise to the building services industry. The most intensive use of energy in a building usually results from heating or cooling spaces.
The HVAC industry has therefore been working hard on developing energy efficient products and strategies, spurred on by a culmination of tightening legislation and soaring fuel costs.

Energy efficient products, such as underfloor cooling, are now being recognised as the way forward by end users and the building services industry alike. Where mechanical heating and cooling is required, underfloor air conditioning can make a major impact in cutting the fossil fuel consumption typically required by VAV or fan coil air conditioning. Studies both in the UK and the Far East show as much as a 30% reduction in electrical consumption is possible when the Flexible Space Concept, incorporating Hiross underfloor air conditioning, was compared with traditional VAV.

Although there is no question that the building services industry should be employing energy efficient products, such as underfloor air conditioning, the construction sector should also be looking at the whole energy picture. Not only should each individual product’s energy efficiency be considered but the product’s impact on the sustainability of the whole building. Some 10-20% of energy used in a building’s lifetime is in the form of embodied energy incorporated in materials and in the building process. Using fewer materials and shortening the build process through using advanced technology, like underfloor air-conditioning systems, is one obvious way to enhance the sustainability of building construction.

However, another way to make further dramatic energy cuts is by reducing a building’s height by 10%, but to achieve this you need to re-think a building’s air conditioning. Standard air conditioning takes up about 600mm (2 feet) in a false ceiling. In addition to this space requirement most intelligent offices now use raised access floor for cable management, increasing a buildings height by a further 150mm (6 inches) per floor. If designers rethink this use of space and increase the floor void by another 150mm (6 inches) while using this void as a plenum to distribute conditioned air to the office space as well as the cables and other services, this could actually result in an overall reduction in building height. Using a raised access floor instead of a false ceiling for air-conditioning, ventilation, cable and power distribution services brings a net height saving per floor of approximately 450mm. Typically, this equates to a reduction in the building height of as much as 10-15% – a dramatic saving on high-rise buildings. This means developers can achieve the same lettable floor area for their investment while generating huge reductions in component and labour costs and dramatically shortening the whole construction programme time.

One of the world’s landmark skyscrapers is testament to these benefits, The Center in Hong Kong stands 352m and 80 storeys high. It is the fourth tallest building in Hong Kong and provides over 90,000m2 of high quality office space. The building is equipped with AET’s Flexible Space Concept, incorporating Hiross underfloor air-conditioning technology. The application of the Flexible Space Concept offered a saving of 35m in height when compared with conventional VAV, the equivalent to a 10 floor office block. This resulted in approximately US$5 million saving on the cost of curtain walling alone, with further savings coming in reduced vertical components, such as, lift shafts, stairwells, risers and structural elements.

However, the energy savings don’t stop there. Once a building’s height is reduced by 10% it receives 10% less solar gain which means chillers and air handling plant can drop in size. In turn this means a building’s power supply can be slashed resulting in less demand for the power station, so it will produce less power and pollution.

Meanwhile, the energy required to mine and produce the materials to construct the building will be similarly reduced with fewer trucks needed to deliver the materials. As a result of fewer trucks there will be less street congestion and so less wasted fuel for other road users.

The world population is increasing at about 1 billion every 10 years and with the escalating threat of climate change now is the time to take stock and make changes.