High-Rise Buildings: Energy Consumption and GHG Emissions
Among the criticisms levelled at tall buildings is that the high quantities of structure and materials required to support, clad, and service them, coupled with energy intensive construction at height (Oldfield 2010). In different building phases, GHG emissions are responsible for the high use of energy. This takes into account two types of main energy consumption: (1) embodied energy, and (2) operational energy and comparing these two aspects to other building types.
Tony Arnel, Chair of Green Building Council of Australia (GBC-Australia) and the World Green Building Council World (GBC) challenged the high-density vision for our cities. He stated that high-rise buildings were not more sustainable than the suburban home. According to Arnel, a study suggested that buildings above three storeys begin to use more energy due to the need for lighting in common areas, lifts, security, and the lifestyle of residents (http://www.thefifthestate.com.au/innovation/ energy/high-rise-living-%E2%80%93-is-it-the-Sustainable-answer/20345). The NSW Energy Australia study found that a high-rise apartment uses 30 % more power than a typical detached house, much of it in common areas such as foyers and car parks. On the question of water use, Sydney water statistics show that multi-unit dwellings account for 14.3 % of Sydney’s water consumption compared to 45.7 for single dwellings. Nevertheless, a recent energy and water audit by Willoughby Council of the common areas in 25 Sydney multiunit buildings showed that high- rise buildings generated four times as much CO2 as villas/townhouses and three times as much as low- and medium-rise buildings (http://www.thefifthestate.com. au/innovation/energy/high-rise-living-%E2%80%93-is-it-the-Sustainable-- answer/20345). Regardless of the large number of people a tall building can shelter, the overall use and intensity of use of both power and water was much greater in high-rise buildings than in low-rise buildings. The Willoughby Council concluded that this was potentially due to “the additional centralised plants and equipment that often occur in high-rise buildings, such as swimming pools, spas, saunas, cooling towers, pumps, and lifts”. Also it stated that “the high energy usage may also be attributed to the arrangement of central hallways and underground car parks in high- rise buildings which generally have no natural light and must be lit and ventilated at all times to ensure safety and amenity for the large number of occupants”. Nonetheless, it has been seen when advance green technologies are incorporated in the four leading tall buildings, namely 30 St. Mary Axe (Gherkin’s)—London, UK; Gensler’s Shanghai Tower—Shanghai, China; the Passivhaus RHW.2 Office Tower—Vienna, Austria; and The Shard Tower—London, UK (Figs. 9.12, 9.13, 9.14 and 9.15), power, energy, and water uses, and CO2 emissions were significantly reduced but that depends on innovative solutions.
In this regard, embedded energy is another issue. According to a study conducted a decade ago, researchers at the School of Architecture, Deakin University, and the School of Architecture, University of Tasmania, found that high-rise buildings had 60 % more energy embodied per unit GFA in their materials than the low- to medium-rise buildings. While this figure has improved due to improved manufacturing processes, embedded energy is still greater in tall buildings because of the higher load requirements (http://www.thefifthestate.com.au/innovation/energy/ high-rise-living-%E2%80%93-is-it-the-Sustainable-answer/20345). But nevertheless, the Corporation of London, as the local municipal authority indicated that tall office buildings are becoming increasingly necessary as a result of the efficient use that they make of the limited land available (Will Pank et al. 2002). In this context, the primary design concern for many tall buildings is their operational efficiency rather than their environmental impacts; hence a balance is needed between these two factors. In London where buildings are accountable for 75 % of energy use, lifts use about 10 % of a tall building’s energy, whereas lighting is liable for about 20 % (Will Pank et al. 2002).
Life cycle assessment (LCA) of buildings and construction materials is gaining weight. About 10-20 % of the energy consumed in buildings over their lifetime is in the form of embodied energy incorporated in materials and the process of the building itself. Lifecycle analysis shows that much can be done to reduce the embodied energy of buildings, particularly in tall buildings with repetitive floor plans and large areas of the facades. Whilst there are advantages and disadvantages of building tall, the potential for improving the sustainable development of new high-rise buildings in cities is immense (Will Pank et al. 2002).
The impact of global warming and uncertainty over long-term energy supplies makes it vital to find means of reducing energy. It is important to notice that most office buildings’ energy consumption over its lifetime lies in lighting, lifts, heating and cooling, and computer usage. Buildings in the City of London can be made more sustainable by architecture that responds to the conditions of a site with integrated structure and building services. The fossil energy use in buildings can be reduced by effective use of passive solar heat and the thermal mass of the building,
Fig. 9.17 Embodied energy of five office buildings in Melbourne, Australia. Source: (http://www. emerladinsight.com/doi/pdfplus/10.1108/02632770110387797)
high insulation levels, natural daylighting, and wind power can all help to minimise. In tall buildings, maximising daylight can be achieved by making floor plans narrow rather than deep. However, office buildings in the City of London can consume 1000 kWh/m2 or more per year for heating, hot water, lighting, and computers (Will Pank et al. 2002). In contrast, one of the Europe’s tallest buildings is the Commerzbank building in Frankfurt, Germany where all offices have natural ventilation and opening windows to assist in reducing energy use and succeeding in creating a pleasant and energy-efficient working environment (Will Pank et al. 2002).
A well-referred study by Treloar et al. (2001) examined the initial embodied energy in five office buildings in Melbourne, Australia—3, 7, 15, 42, and 52 storeys in height (Fig. 9.17). It showed that two of these high-rise buildings have approximately 60 % more embodied energy per unit gross floor area than the two low-rise buildings. Furthermore, the same study identified the embodied energy in the structural building elements (columns, walls, etc.) and energy from the construction process as increasing with height, whilst other building elements (such as substructure, windows, and finishes) did not appear to be influenced by the building height (Foraboschi et al. 2014). Also, embodied energy per unit floor area increases with the storey height (Foraboschi et al. 2014).
In 2014, Paolo Foraboschi et al. conducted a study on sustainable structural design of tall buildings. This study was based on the embodied energy where the consumption is measured by the energy required for tall building structures (20-70 storeys). It is expressed in terms of cradle-to-gate embodied energy which shows that if some design decisions are dictated by the embodied energy, the premium for height of the embodied energy is not substantial, proving that tall building structures can be sustainable. However, a structure with the lowest weight does not imply the lowest embodied energy. It becomes clear from the study that embodied energy depends mainly on the flooring system where steel consumes more embodied
Fig. 9.18 Breakdown of electricity end-user in selected office buildings in Hong Kong. Source: Lam et al. (2004)
energy than reinforced concrete. Embodied energy is ultimately confirmed to be a viable tool to design sustainable tall buildings, and the results presented herein may address design issues towards minimising the embodied energy, which means to save environmental resources (Treloar et al. 2001).
Tall buildings use twice the amount of energy used as their equivalent of low buildings. The energy is needed to provide building users with their goods, visitor accessibility, and water supply. This requires electrical energy which leads to more GHG emissions compared to mid-rise and low-rise buildings (Roaf et al. 2005). Figure 9.18 portrays the breakdown of electrical energy end use in selected buildings in Hong Kong. The study includes buildings as high as six floors up to 48 floors (Lam et al. 2004). It is clear that there is a jump in energy use for lifts and escalators, as well as other equipment, but for that of lighting and HVAC there is a slight increase which fluctuates in comparison with those in buildings that are ten and 15 storeys high as shown in Fig. 9.18.