As part of the attempt to achieve our energy and carbon reduction targets, there is a focus on reducing building energy consumption in the UK. Since 87% of existing buildings will still be standing in 2050, retrofitting the current UK building stock is becoming very important. Therefore, the UK Building Regulations are implementing high energy efficiency standards for new, but also retrofit properties. However, 40% of the existing buildings have heritage status, which means they can be exempt from Building Regulations.
This percentage is too significant to ignore and these buildings are major contributors to energy consumption in the UK building sector. Government data from 2006 has demonstrated that older properties have much lower energy performance with over 40% of properties built before 1919 having SAP ratings lower than 41, as opposed to ratings higher than 70 for 60% of the properties built since 1990. There are undoubtedly certain buildings where energy retrofit is not an option. Nevertheless, there are numerous buildings of heritage status, where limited and very careful interventions are not only possible, but also very much needed. For example, regarding solid wall insulation, DECC (Department of Energy and Climate Change), BRE (Building Research Establishment) and the Energy Saving Trust estimate that approximately 69% of the total solid wall area of all dwellings in England could be reasonably and easily insulated and with additional assumptions regarding internal insulation, the potential rises to as high as 97%.
English Heritage is the Government’s principal adviser regarding historic environments, focusing on parks, gardens, monuments and of course buildings. In order to address buildings, it has created listings which can be seen at the National Heritage List for England. Listing is a process that brings a certain building under the consideration of planning authorities so that any potential interventions are thoroughly considered. Listed buildings are divided into three categories, namely Grade I, Grade II* and Grade II. These listed buildings require special consideration by the planning authorities for any intervention.
Nevertheless, there is no specific guidance as to what is allowed in terms of retrofit interventions in each one of the specific categories of listed buildings described above. Therefore, planning professionals must decide on a case by case level, not necessarily having a consistent way of making decisions. In research conducted on thirteen London Boroughs, it has been found that only two of these councils had produced planning guidance specifically for retrofit.
The most common retrofit options for traditional buildings include replacing or installing insulation, windows and door upgrades, electricity and heat generation and finally ventilation improvements. Roof, floor and wall insulation might be applicable in listed buildings and building fabric upgrade is usually the first option to be considered; however, insulation is often technically very challenging. Traditional buildings perform differently compared to modern constructions and usually involve breathing structures, allowing the movement of air through them, unlike what happens with modern buildings. Implementing contemporary practices of insulation and waterproofing in historic buildings might cause adverse effects, such as the development of dampness in the interior of the building.
Similar to insulation improvements door and window upgrades are usually of interest, although not necessarily easy to pursue on listed properties. Double glazing, which is now standard for modern constructions, can improve the thermal performance of buildings, however, in many cases; planning authorities would not allow this level of intervention in a historic environment. Secondary glazing is an alternative to this and it retains the existing window, adding an additional glazing on the inner side of the wall. According to the Energy Saving Trust, this method does not achieve the same level of results in terms of energy performance as double glazing, but it is still a very significant improvement over existing single glazing windows.
There are several options available for electricity and heat generation, which depend upon the building itself and the historic character of a certain area. However, both the exterior and the interior characteristics of a property are bound to change when heating or electrical systems are changed. Other than the obvious external changes when a new technology such as photovoltaics is installed, the interior might be significantly altered, due to the change of radiators or ductwork. As a result, listed properties might be ineligible for such a level of interventions. But it is not only modifications on listed buildings that can be a challenge. The fact that proposed solar panels could be seen from a neighbouring College primarily composed of listed buildings was the main barrier to installing them on a non-listed building in Cambridge.
The measures described above are an attempt to identify the need to retrofit historic buildings and to highlight potential solutions and implications to consider. It is true, there are buildings that are untouchable; however, there are still historic properties that can reduce their energy consumption without sacrificing the things that make them significant.
Image Credit: Steve Evans via Wikimedia Commons.