Implications for existing building stock

The built environment has a design life of 40–100 years and is replaced at a rate of less than 1% per year. This presents a significant challenge over and above considerations when designing a new development, as existing communities need to become more resilient to climate risk through the upgrading of existing stock. Climate projections show that change will continue beyond the end of the century, so even new buildings are likely to need to incorporate strategies for further upgrading over time. Building Regulations have been strengthened in recent years to promote property level resilience to climate change, however, retrospective action is still likely to be required.

Upgrading of the building stock

Wholescale upgrades to building stock is costly and not necessarily effective at the time of implementation. An approach of sequential upgrading should be considered for elements of existing buildings. Different elements have different life expectancies and replacement/maintenance cycles. The upgrade of buildings should be synchronised with this natural maintenance cycle to adapt at least cost to asset owners. For example, when a cladding or glazing replacement is due after 20 to 30 years, adaptation measures should be brought in at this time.

Overheating

Many existing buildings already perform badly in summer. A study by CIBSE and Arup investigated how typical existing buildings would cope with future rising summer temperatures. Existing buildings are already failing to meet comfort criteria in summer months; and some, particularly 1960s office buildings are failing spectacularly. As the century progresses and external temperatures rise, summertime comfort will deteriorate still further.

Retrospective measures are required to minimise energy use for mechanical cooling heat gains as far as possible. For example:

  • Use solar control to keep the sun out during hot days. Fitting external shading control is more effective than internal blinds, however, costs are typically higher and in some instances will be subject to planning regulations.
  • Ventilation air brings heat into buildings when it is hot outside and should be reduced to a minimum during hot periods. Ventilation is only a source of cooling when it is cooler outside. Strategies require secure ventilation pathways (either natural or mechanical) and may be aided by automated, intelligent controls.
  • Many internal gains are unnecessary: switch off lights and equipment when these are not required.
  • Night-time ventilation coupled with closed shutters and ventilators in the daytime can produce lower internal temperatures than outside.

While many buildings can be radically improved through these measures, the fundamental form and structure of some buildings will not allow them to be economically upgraded to offer comfortable conditions in summer. Likely candidates for demolition and replacement might be buildings with low thermal mass, limited ceiling heights or deep plans that rely on mechanical systems to keep them habitable in summer months.

Flooding

Across England, 1 new property in every 11 built was located in an area with a 1 in 100 or greater annual probability of river flooding, or a 1 in 200 or greater annual probability of sea flooding in 2015/16. This is equivalent to 9% of all new builds and has risen from 7% in 2013/14, meaning that a significant number of pre-existing buildings are at risk of flooding despite having been constructed relatively recently.

In addition, an increasing number of pre-existing buildings are in areas of high flood risk as the instances of flood events increase. This was highlighted by the December 2015 floods in northern England and the devastating effects on homes and businesses not previously thought to be at risk of flooding. Subsequently, the ‘Flood Re’ scheme has been set up to help households in such areas to obtain affordable home insurance. An annual tax on home insurers funds the scheme and ensures that flood risk is passed on to Flood Re rather than the insurers. (See also isurv Flood risk.)

Flood risk to existing properties is identified as a red adaptation priority by the CCC in that there is no formal plan yet created on greater resilience and progress is not being made. The CCC also recommend that Defra should take steps to address the increasing number of homes expected to be at high flood risk in the coming decades.

Since 2008, the installation of significant areas of impermeable hard surfacing in domestic front gardens can no longer be carried out as ‘permitted development’, and similar measures for non-domestic premises were introduced in April 2010. The Flood and Water Management Act 2010 made the right to connect to sewers conditional on meeting requirements for sustainable drainage, and introduced the requirement that new surface water drainage should, wherever possible, be dealt with on site using a sustainable urban drainage system (SUDS).