2.1 Challenges The last 40 years have seen much experimentation and significant progress with low-energy building design strategies and technologies. However, in most countries, green buildings are still at a nascent phase of development. Yet they are expected to become the norm in future. Experimentation with net-zero-carbon buildings, passive houses and energy-plus buildings are emerging worldwide. The main challenges facing green buildings are discussed with special reference to the sector’s significant use of resources and emissions of CO2
. This covers both existing building
stock and the projected growth of new construction. A key component of green buildings is related to their location and how they interact with other components of urban and regional systems, which is covered in the Cities chapter.
Sizing the building sector Driven by population growth and urbanisation, the building sector itself is a significant contributor to economic growth, both globally and at the national level. Globally, it is estimated to be worth US$ 7.5 trillion per year or approximately 10 per cent of global GDP (Betts and Farrell 2009) and the construction sector employs more than 111 million people (ILO 2001). At the national level, the sector generates 5-10 per cent of employment (UNEP SBCI 2007a).
There are important differences between developed and developing countries in both the current building stock and projected building-sector growth. Developed country populations are broadly more urbanised and more economically reliant on the service sector than on industry or agriculture. They also have higher household incomes than developing
emissions.
urbanising and are projected to add 2.3 billion to global population over the coming four decades (UN DESA 2009). Of the 9 billion people predicted to live on Earth in 2050, 70 per cent are expected to live in urban areas (UN-HABITAT 2010).
India is short of 24.7 million homes (NHHP 2007; Roy et al. 2007) and the country will need millions of homes to be built over several decades to accommodate projected income growth and urbanisation. New construction growth for commercial and residential buildings currently averages 7 per cent per year in China and 5 per cent per year in India and South-east Asia, compared with only 2 per cent in developed countries (Baumert et al. 2005). As estimates of the global building stock are not available, Figure 1 provides an overview of the scale of residential and commercial floor space in China, the EU, Japan and the USA.
China is expected to add twice the amount of current US office space between 2000 and 2020 (WBCSD 2009). Another study indicates the stock of office space in China as 3.5 billion m2
and predicts it will grow by over 70 per
cent by 2020 (Zhou et al. 2007). In 2007 alone, 0.8 billion m2
projected that in each year to 2020, an additional one billion m2
of new buildings were constructed in China and it is of new buildings will be constructed (Cheng
2010). Global cement production is set to double by 2050, with China and India accounting for nearly half of all production (WBCSD 2007b).
country populations.
Developed countries currently account for the majority of the world’s existing building-related energy demand and CO2
This picture is changing rapidly. Projected economic growth is modest and projected population growth flat or even negative in Western Europe, Russia and Japan. Thus building-related energy demand and CO2
emissions
in these countries will see little growth in the coming decades. There are some exceptions among richer countries such as the United States of America, where higher fertility and immigration rates are expected. In contrast, developing countries are fast-growing, rapidly
Historical trends demonstrate that increasing wealth leads to higher space standards and an increase in household appliances, with implications for energy consumption. Another critical factor in developed countries is demographic and societal change, with a significant increase in one-person households. For example, in Germany, the energy consumption for space heating increased by 11 per cent from 1995 to 2000 before decreasing by 7 per cent from 2000 to 2005 – mainly because of higher energy costs – resulting in an overall rise of 2.8 per cent from 1995 to 2005. Domestic hot-water consumption decreased slightly (by 1.4 per cent) in the period but home appliances still contributed 17 per cent to total energy consumption despite substantial improvements in their energy efficiency. While great improvements in energy efficiency have been achieved in certain sectors, the overall energy consumption of private households in Germany rose by 3.5 per cent between 1995 and 2005 (UBA 2006).