Making and using buildings is our most emissions intensive activity.
Making and using buildings is our most emissions intensive activity. Globally, around 18% of all emissions arise from energy use or industrial processes associated with buildings. These come from heating, lighting and all other processes necessary to make the buildings livable and functional, accounting for 12% of gloabl emissions. The remainder, 6%, is accounted for by the construction of buildings and infrastructure (roads, bridges, tunnels and so on). This requires requires energy intensive materials, particularly cement and steel.
"To reduce the emissions from using buildings, we need to improve the average performance of the stock of all buildings."
Buildings last for many years, so we need to think rather differently about these two causes of emissions. Emissions related to using buildings arise from the entire stock of all buildings in use, including those made up to 500 years ago. However emissions related to constructing buildings, arise only from those that are made in the particular year being considered. To reduce the emissions from using buildings, we need to improve the average performance of the stock of all buildings. This occurs by a combination of modifying (retro-fitting) existing buildings while also improving the performance of new ones. To reduce emissions in making new buildings, we can consider all the options discussed below which includes keeping buildings for longer so that we make fewer new ones.
When thinking about reducing emissions, we need to know which types of buildings should most concern us. To do this, we need four statistics: the emissions per square metre of constructing buildings; the emissions per square metre of using buildings; the number of new square metres each building type made each year; the number of square metres of each type in current use. Of course the figures for using buildings depend on the the local climate, varying from continuous heating in the Arctic, to continuous cooling in Dubai, so the next figure shows how emissions per square metre in use vary for selected building types according to the average local temperature. We’ve added indicative countries to show how these figures are likely to affect national emissions data.
To reduce the emissions associated with using buildings, then given the earlier comments about emissions and energy supply, we have to reduce the energy required to use them. We could:
- Modify the building to reduce the need to use energy to change the internal temperature (by moving towards the highest performing passive building standards, with natural ventilation). Examples of new design, and also of retrofit – Empire State Building, Green Tomato house in London, others?
- Change the technology by which heat (or cooling) is supplied. Comparison and evaluation of claimed and measured performance data for different heat and cooling sources – heat pumps of various types compared to open fires, gas or oil boilers, electric storage heaters etc.
- Modify the target range of internal temperatures (for example by wearing sweaters indoors in winter – in contrast to recent experience, where the users of the best performing buildings choose higher internal temperatures in winter, rather than using less energy to provide their previous temperature. Lessons from indigenous architecture – for example in the Middle East).
- Modify the control of internal temperature in time and space – only using energy to modify the temperature for the particular times and areas when the space is occupied. This could include reducing effective ceiling heights and reducing the...???
Within the UK, our current average energy requirement for using space in homes, offices and retail space is around 18555 kWh per year per dwelling. The average dwelling is 100m^2, thus 185.55 kWh/m^2. Instantaneous consumption is thus 210 W/m^2 for homes. In commercial space, the emissions associated with use are 84 kg CO2/m^2/year. However, we know how to design and build buildings that require one tenth of this. We therefore need to take two major actions:
- Change the performance of all new buildings by imposing standards on builders and verifying that they achieve them in practice; to retrofit old buildings to meet the same standards. This can be implemented now, by national and local government, and it should be a policy priority to do so despite the lobbying of the incumbent construction industry. In the UK, land prices are much higher the costs of construction, so imposing the additional (relatively small) cost of high performance on new buildings, will make relatively little difference to their total price.
- Raise the performance of the stock of all existing buildings to these same standards. This is a manufacturing problem – and as yet no one has designed an economic means to retrofit houses fast enough, and at an appropriate cost, to motivate wide uptake. In an energy crisis, we would solve this problem very rapidly due to necessity, and it should be a priority for research and development.
"For older housing in the UK with poor energy performance, we need to balance the decision between energy invested in retrofit and the resulting energy saving in use."
Heritage buildings in the UK can be maintained indefinitely, are an essential part of our national and local identity and can be adapted to new uses by sensitive redesign. However, we are currently careless of our new architecture; new commercial buildings constructed in the UK are built for a life of 100 years but on average are knocked down and replaced after just 40. For older housing in the UK with poor energy performance, we need to balance the decision between energy invested in retrofit and the resulting energy saving in use. This requires careful accounting for the balance between emissions associated with the stock of buildings and the emissions associated with using them – and we’re currently working on the best way to assess this balance. However, for any new construction there should be no choice. Local planners should be imposing design conditions on clients, architects and constructors to ensure that permission to build a new building is always conditional on the building being useful and wanted for at least 200 years. This could be implemented by local government immediately.