On current trends, carbon emissions associated with air conditioning in the UK could quadruple over the next twenty years. How could legislation and market transformation programmes reduce the risks?

Design trends are seeing a shift away from reliance on mechanical cooling. As buildings become more energy efficient they emit less carbon, thereby reducing the long-term impact of buildings on the global atmosphere.

However, while these improvements will mean a gradual decline in carbon emissions, they are outweighed by an underlying increase in the number of refurbished buildings being equipped with mechanical cooling.

Assertive control, in the form of tighter Building Regulations and minimum equipment efficiency standards, could feasibly reduce carbon emissions from air conditioning in 2020 by 35% compared to a “business as usual” view of the future.

Market scenarios

Analysis carried out by BRECSU for the Market Transformation Programme (MTP) of the Department of the Environment, Transport and the Regions (DETR) has identified the scope of the problem.

In the last 20 years, average fossil fuel use per square metre of floor area in commercial buildings has fallen by about 30%. However, electricity use has increased to a point where it accounts for over 50% of carbon emissions from non-domestic buildings. One of the reasons is the increasing use of air conditioning. Another is the increase in IT loads and the consequent rise in cooling loads. Already, air conditioning accounts for about 14% of carbon emissions from commercial buildings.

Only about 10% of commercial floor space is currently air conditioned, so the growth potential is considerable. Unsurprisingly, property developers find it an essential element of specifications. Rates of installation in existing offices also appear to be rising fast. On this basis three market projections can be considered: a reference scenario, an economic and technical potential scenario, and a policy target scenario.

The reference projection is essentially a business as usual scenario, extrapolating historical trends. This shows gradually rising sales of first time installations in new and existing buildings leading to increasing market penetration over the twenty-year timescale. By 2020, energy use and carbon emissions are about four times those of today.

The economic and technical potential scenario is on the basis that air conditioning is not essential in 75% of office space. Natural ventilation or limited mechanical ventilation is theoretically adequate so minimal air conditioning is assumed.

This scenario would require a decrease in air conditioned space, with at least some air conditioned buildings having mechanical cooling removed during refurbishment. In addition, all new installations would be significantly more efficient than is typical today.

On these assumptions, energy use for air conditioning in 2020 would be 80% of today’s level.

In the policy target scenario, energy efficiency regulation is progressively introduced over the twenty-year period. This is done in the form of whole-building regulations (in practice probably Building Regulations) and minimum efficiency requirements (probably via European initiatives).

These measures affect not only first-time installations, but also system replacements. They result in a 35% reduction in the 2020 emissions and energy figures compared to the reference scenario – but this is still a substantial increase from where we are today.

These scenarios ignore any impact of global warming – other than observing that concern over its possibility may strengthen beliefs that comfort cooling is desirable.

In reality, relatively small increases in maximum outdoor temperatures could tip the balance between natural ventilation and mechanical cooling.

Market transformation

The Government’s Market Transformation Programme is examining how energy consumption and carbon emissions might develop over the next two decades, and what policy options exist to limit or reverse growth. The programme covers most types of energy-using equipment, from domestic appliances, lighting, boilers and other traded goods to air conditioning.

The figures quoted above come from three scenarios considered by the programme and published in a sector review paper.

Government is keen to solicit views, either through the media or directly to BRECSU. The aim is to produce a generally accepted view of the potential growth in energy use and carbon emissions, on policy options, and on the extent which possible options could impact on consumption.

As the creation of scenarios inevitably involves some uncertain assumptions, views and information on some of the key issues would be particularly welcome, such as:

  • what is the maximum proportion of the building stock that might potentially be air conditioned?
  • for how much of the building stock is air conditioning essential?
  • what efficiency improvements are technically and economically feasible?

It would also be helpful to have measured energy use figures for air conditioning compressors.

This research will be presented at the CIBSE/ASHRAE Conference ‘20:20 Vision’ in Dublin in September. For more details contact the CIBSE Events Department on 020 8675 5211, or e-mail: events@cibse.org

The research will shortly be available on the Market Transformation Programme web site: www.mtprog.com