Go Figure

While most of us accept that energy use has risen in leaps and bounds in recent decades and that this has had an impact on climate change, the figures still have the potential to shock. One frightening statistic is for worldwide primary energy use. This rose by almost 50% between 1983 and 2003, and according to figures gathered by the Energy Information Administration (EIA), the trend is set to continue at a startling pace.

Predictions are that the energy use in emerging economies will grow at an average annual rate of 3.2% and will exceed the energy use of developed countries by 2020. China is particularly striking: it has taken only 20 years to double its energy consumption.

Energy-hungry buildings

Along with industry and transport, buildings are among the most prolific users of energy. If emerging economies follow the pattern of the developed world, their buildings are set to grow in number significantly (figure 1, page 40).

Buildings in developed countries account for 20-40% of total energy use. For example, in 2003 buildings accounted for 37% of total energy consumption in the EU, a figure bigger than that of industry, at 28%, and transport, at 32%. The figure for buildings in the UK stood at 39%, a figure whose size is partly due to the country’s shift away from heavy industry and towards service sector activities. In contrast, the figure for Spanish buildings is only 23%, 14 points below Europe’s average. But that figure is expected to rise as economic growth leads to convergence with the rest of Europe.

In its 2005 International Energy Outlook, the EIA analysed and forecasted trends in building energy consumption. It expects this to grow by 40% in the next 20 years, an average yearly increase of 1.7%. By then, consumption in dwellings and non-domestic sectors will be around 65% and 35% respectively. Forecasts are that both developed and emerging economies will be balanced in their use of energy for dwellings by 2025. In addition, as emerging nations economies grow and their trading and populations rise, their needs for education, health and other services will intensify and result in a rise in energy consumption. Energy use in the service sector in these countries should double in the next 20 years, with an annual average growth rate of 3.6%.

HVAC systems

One of the biggest factors in the growth of energy consumption is HVAC systems. These systems, considered a luxury not long ago, are now essential. HVAC is the largest energy end-user in both the residential and non-residential sectors, accounting for around half the energy use in buildings and a fifth of the total national energy use in developed countries. As if that’s not enough, predictions indicate a massive growth in energy consumption and air-conditioned buildings in the EU in the next 15 years.

For example, space air conditioning in dwellings in Spain accounts for about half of the country’s energy consumption, or more than twice the amount for heating domestic water. For non-domestic buildings, the IDAE (part of the Spanish Ministry of Economics) estimates HVAC energy consumption to be 48%, a figure still lower than the 57% of the US. At the European level, the extent of HVAC is unknown, but many sources show a big rise in the use of air conditioning, especially in southern countries. Spain and Italy account for more than 50% of the European market, creating serious supply difficulties during periods of peak loads.

One difficulty that Europe faces is a lack of data on national, regional or local energy use. This would allow efficient planning of energy policies for buildings and the coordination of measures to address each of the end-uses. Ideally, Europe needs analysis by sector. Funding for this must come from governments so that a comprehensive database of the building stock and energy parameters can be built up to create a basis for planning.

Non-domestic buildings

The type of use and activities in non-domestic buildings make a huge impact on the quality and quantity of energy services needed. But few sources offer data by typology, and there is no consensus on a universal classification. This makes analysis very difficult.

Yet it is possible to make general conclusions. In the UK, energy consumption in the building sector has stabilised somewhat in recent decades. Increases in efficiency have offset increases in floor area and increased servicing levels. In the rest of Europe, energy consumption in the commercial sector is growing at a higher rate than in other sectors, mainly because of the expansion of HVAC systems in new buildings. In the UK, new build rates in the service sector are typically around 2% per year. Spain’s average annual growth rate since 2000 has been 6.1%. Forecasts are that this growth will continue. In 2003 the building sector accounted for 11% of total energy use in the UK – a proportion equal to the EU level – compared with 18% in the US. Energy policies have focused on the residential and industrial sectors and have tended to overlook the service sector (which includes buildings), despite it showing the highest growth.

Office and retail are the most energy intensive structures, typically accounting for over 50% of the total energy consumption for non-domestic buildings. Hotels and restaurants, hospitals and schools follow.

HVAC is the main end-user of this energy, accounting for close to 50% of use. Lighting follows (15%), and then appliances (10%). The type of building is critical in determining the distribution of energy end-uses and their energy intensity, which makes the development of independent studies according to building types all the more essential.

Office buildings

Within the commercial sector, office and retail buildings consume the most energy and emit the most CO2. In the US, these buildings account for 18% of total non-domestic area and about 20% of the energy use, equivalent to 3.4% of the total consumption. In Spain, on the other hand, they account for a third of the commercial sector’s energy consumption and almost 3% of total energy consumed. The figures are similar in the UK: 32% of energy consumption and 4% of total energy use.

Various factors have contributed to this total, such as economic prosperity, which has substantially increased the total built area of office buildings, and many business developments have cropped up on the outskirts of major cities. Between 1990 and 2000, Spain built 9.3 million m2 of new office space. In the UK, the total floor area of commercial offices rose by 23% between 1999 and 2005, although the typical annual growth rate in more recent years has been a more modest 1%-2% per year.

The requirement for artificial lighting, IT equipment and air-conditioned areas has, unsurprisingly, steadily increased. In Spain virtually all new offices are air conditioned. Even milder climates such as the UK have air conditioning in half of new offices.

The energy consumption pattern of office buildings is more or less uniform across the building stock. HVAC, lighting and office equipment represent the three key energy end-uses, adding up to about 85% of the total use.

Proliferation of energy consumption and CO2 emissions in the built environment has made energy efficiency strategies a priority. The HVAC system is now an unavoidable asset, but it has brought with it an associated energy consumption that accounts for almost half the energy consumed in buildings, and 10-20% of total energy use in developed countries.

The built area and its associated energy needs are expanding. The trend in the growth of energy use in buildings will continue as long as resources or economic growth allow. Government must intervene by promoting energy efficiency and new technologies for energy production by limiting energy use and by raising social awareness of the rational of consumption. These will be essential measures to create a sustainable energy.

The biggest hurdle is that although the energy use of buildings in developed countries is high - above the consumption by industry and transport in some states - data is still insufficient and fails to reflect the sector’s importance, and this lack makes it difficult to understand the underlying changes affecting energy use. Unlike transport and industry the sector is not considered independent. Suitable analysis and the efficient planning of energy policies for the future requires comprehensive building energy information to be made available.