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Energy efficiency, retrofitting, and sustainable construction supplementary planning document


Bath and North East Somerset Council has declared a climate emergency and has committed to providing the leadership for the district to be carbon neutral by 2030.

This will contribute to the UK’s legally binding target of net zero carbon by 2050. There are three key priorities to achieve this:

  • Energy efficiency improvement of the majority of existing buildings (domestic and non-domestic) and zero carbon new build
  • A major shift to mass transport, walking and cycling to reduce transport emissions
  • A rapid and large-scale increase in local renewable energy generation

This Supplementary Planning Document (SPD) accompanies the core aims of this resolution, in addition to the Local Plan and Draft Core Strategy Policies SCR1: Retrofitting and CP2: Sustainable Construction.


There are five main aims for this SPD:

  • Provide simple, practical guidance on retrofit and sustainable construction for all building types whilst having regard to statutory legislation
  • Facilitate all householders and small-scale developers to approach build projects more sustainably
  • Support the uptake of retrofitting measures
  • Support planning, housing, building control and conservation officers to provide consistent and quality advice
  • Enable our goal of achieving 65,000 retrofits in B&NES by 2030


We seek to encourage retrofitting measures to existing buildings to improve their energy and water efficiency and their adaptability to climate change. Support for appropriate domestic scale renewables is also important.

This Supplementary Planning Document profiles the the main building types found in Bath & North East Somerset, and explains through diagrams how they are built and what materials are used.

We have a number of energy efficiency quick wins that provide cheap or free energy and water improvement solutions which home owners and occupiers can implement immediately. You can then consider which retrofitting options you might like to use.

We encourage and enable the sensitive retrofitting of energy efficiency measures and the appropriate use of microrenewables in historic buildings (including listed buildings), and in Conservation Areas whilst also safeguarding the special characteristics of these heritage assets.

Energy efficiency and the historic environment

It is widely recognised and accepted that the historic environment should play its part in meeting these current and future challenges. However, it is vital that changes are consistent with the aims of heritage protection and the statutory duty of care placed on the Local Planning Authority (LPA) by primary legislation and government policy.

In accepting that some change will be necessary it is critical that this is carefully managed so that the historic environment and the heritage assets that it is made up of is sustained as cultural heritage for present and future generations. Historic buildings are a finite resource and are inherently sustainable having been, in most cases, well-constructed from high quality, locally sourced materials by local craftsman.

Their inherent embodied energy (the energy expended and encapsulated within the fabric of a building in its construction) means that their retention and care is both logical and consistent with modern concepts of sustainability and with the ambitions of reducing carbon emissions.

Traditional buildings and their need to ‘breathe’

It has been long recognised that traditionally constructed buildings utilising a solid wall construction (generally considered as buildings constructed before 1919) need to be able to ‘breathe’.

The word ‘breathe’ in this sense means permeability and the ability of moisture to move freely, unhindered, throughout the width of the wall. This mechanism relies on moisture being able to evaporate into the external and internal atmospheres.

Internally moisture evaporates and enters the internal environment and relies on good ventilation to be evacuated into the external atmosphere. This process is critical for the health of the building and its occupants and relies on a number of factors in order to function properly including: permeable materials such as lime mortar, lime plaster, traditional permeable paint finishes and traditional, passive ventilation routes such as chimney flues and natural ventilation in doors and windows.

If non-permeable materials are used such as cementitious mortar, gypsum plaster, modern impermeable paint finishes and traditional ventilation routes are blocked this will result in high levels of moisture and condensation to the detriment of the health of the building and its occupants. High levels of moisture trapped in masonry walls will lead to increased heat loss, discomfort for the occupants and may harm interior fixtures, fittings, finishes and structural timbers.

Whilst it is recognised that excessive drafts can cause discomfort for the occupants of a building it also needs to be recognised and understood that hermetically sealing a traditional building, in the manner of modern building construction, could cause significant problems for occupants and buildings alike. In proposing thermal upgrading measures an understanding of the needs of a traditionally constructed building need to be understood. For instance, care must be taken when improving thermal efficiency through draft proofing not to create a barrier to a sufficient level of ventilation.

We advocate that owners of traditionally constructed buildings undertake an assessment of the needs of the building based on a thorough understanding of how it is constructed and how it is ventilated.

Sustainable construction

We would like to ensure that all design, construction, and build projects use sustainable construction principles. For larger scale developments, specialist expertise can often be employed or known methodologies can be used such as Code for Sustainable Homes, Passivhaus or the Building Research Establishment Environmental Research Methodology (BREEAM). Find out more about sustainable construction principles on our web pages.

There are opportunities for almost all build projects, large or small, to be more sustainable and this document introduces and explores, in pictures, the key sustainable construction principles. These principles are founded on the well-established methodologies.