The shortage of housing, particularly for people on low incomes, is a major issue. The extent of the shortage is made visible by the number of homeless people forced to sleep rough on the streets. According to research by the housing charity Shelter, at least 320,000 people are homeless in Britain, with more than 4,000 of these sleeping rough. The need for council housing vastly outstrips supply, with around 1.24 million UK households on local authority waiting lists.
But the urgency of the climate crisis means that we should also be concerned about the amount of energy a household uses and the amount of energy used in the construction of new houses.
Buildings consume about 40 percent of all energy generated. Of this, about one-third is used in commercial buildings and two-thirds in domestic ones. A house will use energy for both heating and cooling, to cook the food, heat the water and run the services. It will also emit energy through walls, windows, roofs and chimneys. Together such usage is a dwelling’s in-use energy.
Buildings that are designed for cold climates must be well insulated to keep the heat in the building. But in hot weather this can cause problems which are exacerbated by global warming. Many low-energy buildings built to keep warm in winter overheat in warm weather. The heat from the sun and increased outdoor temperatures raises indoor temperatures and makes the occupants too warm.
This can often be dealt with using shading and allowing cooling outdoor breezes into the building, but designers tend to use air-conditioning in order to control indoor temperatures. In a vicious cycle, this increases the energy use of the building, adding to the greenhouse gases that are partly the cause of the problem.
In hot climates, people will have developed ways to deal with the temperature and, in theory at least, their buildings are often designed to do this. Local customs and culture can also help to deal with temperatures that would be unbearable to people used to cooler climates. Unfortunately, many of these hot-weather building techniques have been lost in the drive to make buildings cheaper to build, forcing occupants to resort to air-conditioning, adding more to carbon dioxide emissions.
If built to a high standard — well insulated and with efficient appliances — a dwelling may emit as little as 12 tonnes of carbon dioxide over the next 50 years. Houses built to current building standards will emit about twice this and older buildings may emit far more.
The exact figures will vary from place to place, country or climate, and according to local economic and social conditions. In the US, 80 percent of new dwellings are built with air-conditioning, while in the mountainous areas of Nepal people live at indoor temperatures below 10°C.
The other factor that typifies buildings is that they last a long time, so most of the houses that will be in use in 2050 have already been built and occupied. Typically, new houses built each year will constitute only about 1 percent of all buildings.
In the past, dwellings would be made of locally sourced wood or stone. But with the growth of fossil energy many aspects of building — transport, brick, concrete and steel etc have been developed into profitable, large-scale industries whose products are trucked to site. Some types of buildings are even fabricated offsite. The energy the occupants use has also increased due to the use of coal and gas to heat and light homes — and to generate electricity.
The use of open fires meant that houses were particularly inefficient. Not only did much of the heat go up the chimney, but fires need air to stay alight, and this was drawn in through leaky windows, causing the chronic draughts for which Victorian buildings were famed. The insulation of the walls was not seen as particularly necessary.
One response to the increased use of central heating in buildings has been insulation. This meant that houses began to be built with double-skin walls in order to improve insulation and increase indoor temperatures. Since then, building regulations have gradually tightened to increase wall insulation, replace single-glazed windows with double-glazing and legislate for more airtight buildings.
But the problem has not only been the amount of energy a dwelling consumes and emits but also the energy used to build it – to mine the materials it is composed of, to transport them to the site, to shape them into a dwelling and provide services such as power, drains, roads and so on. The energy embodied in a new, well-built, energy-efficient house can typically be the equivalent of 40 tonnes of carbon dioxide.
Embodied energy exists in every building. The construction and technology of older buildings meant that the amount of energy they emitted compared with the amount of energy they embodied was much larger than it is for modern buildings — especially when spread over the 60 or more years the building could be expected to last. So, the focus has always been on cutting the in-use energy by using insulation, shading and, in fine weather, opening windows in order to avoid the need for heating and cooling.
The in-use energy for modern buildings, especially those built to a high standard with a lot of insulation and technology such as heat exchangers, can be much lower than that for older ones. But their embodied energy can be much larger.
For example, using current building regulations, a dwelling’s embodied energy is similar to or greater than the energy in-use over 60 years. A high-spec house can have embodied energy that is three times greater than all the in-use energy it is expected to consume over the next 60 years.
The embodied “part” of the carbon footprint of a building, which is usually assumed to be balanced out by the energy savings over the lifetime of the building, is actually associated with the time it takes to build — say the first year or two.
Building new houses is an expensive business in terms of the carbon produced. Replacing old houses with new, which many developers propose, is even more catastrophic because the embodied energy of the old dwellings is effectively thrown away.
In the short term we must cut emissions as much as possible — at least until energy production escapes from its dependence on fossil fuels. For buildings this means reducing new building to the minimum. There is no doubt that houses are needed, but we should start by adapting existing — and often empty — buildings as living spaces.
The very worst response is to knock old buildings down and build replacements. This adds to carbon dioxide emissions as well as destroying existing housing. Sadly, owners and developers carry this out in order to increase building values; often with the approval of local authorities eyeing the subsequent increase in council taxes.
Many of the empty buildings in inner cities were built not as places for people to live or work but as places for rich landlords to invest their money. In the strange world of finance, the fact that the empty and unused buildings can be sold for an ever-increasing amount is equivalent to a profit. This is why the finance pages react to a fall in property prices as a tragedy while for the rest of us it can only be a good thing.
There are three ways to solve the housing crisis without building new homes. First, improve the performance of existing buildings, many of them built before there were building regulations. The Campaign against Climate Change’s pamphlet One Million Climate Jobs suggests that the workers whose jobs are lost by any slow-down in construction should be employed to improve existing buildings. Reductions in in-use energy are much easier to achieve than in embodied energy. And of course, the reductions really are achieved over the lifetime of the buildings.
Second, compulsorily purchase empty unused buildings at realistic prices and use them for housing. That way we get more places to live with relatively small increases in carbon emissions.
Third, use buildings and their sites to harvest natural energy using solar heaters and solar power from photovoltaics. The surrounding earth can also be used to store heat in the summer and cool in the winter, spreading out the energy use of a building over the year.
All of this can be done now. The way improvements are currently financed, by individual building owners or occupants one-by-one, is guaranteed to maximise cost. Individual homeowners are often unable to afford the cost of the work. It is even worse when a landlord who has no incentive to carry out work owns a building.
The work needed to achieve the necessary reduction in carbon dioxide could be done by groups of workers –— engineers, designers and builders undertaking improvements in a coordinated way and financed to work from street to street. This will get the work done as fast as possible and cost considerably less.
The need for housing is urgent, but the implications for the best way to avoid increasing energy use in the most energy-intensive part of the economy will require careful planning and generous investment. We cannot rely on profit-driven developers and house builders in the private sector. National and local government will be needed to drive a rationally coordinated plan of action.
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