Objectives of the Project

The objectives for undertaking building work may impact the proposed energy efficiency measures. Objectives and ambitions may include:

  1. Complying with Building Regulations
  2. Increase the EPC rating
  3. Reduction in energy bills
  4. Improvement of occupant’s comfort levels
  5. Sustainability and reducing the carbon footprint

For example, reduction in energy bills and carbon footprint may be achieved by minimal intervention, whereas needing to comply with building regulations and achieving U-values may require increased amounts of insultation with limited choices (subject to location and build up required). There are exemptions and particular considerations for historic and traditional buildings within both Building Regulations and Energy Efficiency Regulations. Refer to Historic England’s guidance:


Standards, Approaches and Guidance

To achieve the objectives of energy efficiency the following existing guidance and standards can be used:

PAS 2035 Retrofitting dwellings for improved energy efficiency

PAS 2035 is a British standard and provides a framework for preparing plans for domestic retrofit projects. Any retrofit designs that emerge from its specifications must be installed in accordance with the requirements outlined in PAS 2030.

PAS 2035 was commissioned following the recommendations in Each Home Counts and takes a whole house approach. It can be adopted by all professionals and contractors involved with recommending, managing and implementing energy efficiency measures. As well as the requirement for retrofit professionals and contractors, such as Retrofit Assessors.

Importantly the standard can be used with retrofitting traditional building, takes into consideration of the condition of the existing building and provides an overview of the interlinking measures and if they are compatible.

The BSI and Retrofit Academy provides further information on PAS2035.

Whole House Approach

The Whole House Approach has been developed by the Sustainable Traditional Buildings Alliance and is advocated by Historic England, Historic Environment Scotland, Cadw, RICS and RIBA. The approach has been endorsed by the UK Government through the Each Home Counts report from 2016.

For the Whole House Approach, any decision regarding energy efficiency measures should be a balanced judgement, taking account of the energy savings and environmental improvement; the heritage protection and building fabric; and enhancement and the health of the building and occupants.

Whole House Approach does not have requirements on space heating, heat loss or airtightness, working instead to balance the different aspects based, on the objectives of the project on the individual and their comfort levels.

Low Energy Building Standards

There are a number of low energy building standards that were first developed for new buildings and have high demand on achieving targets relating to space heating. Passivhaus is a renowned design that was founded in Germany. It is a low energy building that uses airtightness, thermal bridging and mechanical ventilation with heat recovery, with renewables resulting in requiring no or very little carbon emissions to function. It is designed using the Passive House Planning Package software. EnerPHit was developed by PassivHaus and uses the same principles. It was launched in the UK in 2010 for retrofit, recognising that the requirements of PassivHaus cannot be achieved in all buildings, for example installing triple glazing. The Association for Environment Conscious Building (AECB) produced a Retrofit Standard (previously known as the Silver Standard).

EnerPHit, AECB and Passivhaus is an energy specification, promoted as a standard and a scientific design tool. The starting position is to understand the existing condition of the building before works begin (similar to the Whole House Approach). However, there is little regard to the material being inserted, for example the type of insultation and the compatibility. There is high demand to make the building airtight with limited thermal bridging. 

Whilst there have been a number of EnerPHit and AECB Retrofit Standards as case studies that have been achieved, this is a high-risk approach. When the work is being carried out, it needs to be undertaken by experienced and appropriate contractors as any details that are not properly managed can result in a detrimental impact to the occupant’s health and the building. For example, timber beams within walls not appropriately managed will have an increased risk of deterioration from moisture build up. This high-risk approach is informed by energy modelling software and pushes traditional buildings to standards they were not constructed for.

Historic England Energy Efficiency Series

Historic England have been a leading public body conducting research regarding performance of existing buildings, energy efficiency, retrofit and sustainability. As a result they have produced a wealth of research papers, advice and guidance. They have produced a suite of free technical advice and guidance documents on retrofitting historic buildings to improve their energy efficiency. This includes general improvement to more detailed advice on installing insulation.

Their principles follow the Whole House Approach. They advocate certain retrofit strategies, specifically those for modern construction, are not appropriate for traditional buildings.

Sustainable Traditional Buildings Alliance Guidance

The Sustainable Traditional Buildings Alliance have produced the Knowledge Centre as a resource for retrofitting Traditional buildings. The information provided is for assisting decision making and to increase knowledge about responsible retrofit.

Using the principles of the Whole House Approach, STBA have produced the Responsible Retrofit Guidance Wheel. This is an invaluable source that outlines the advantage of each measure, as well as demonstrates how each energy efficiency measures interlinks and the technical, heritage and energy concerns that can arise. The concerns are measured from minor to high. For example, proposing loft insulation has eight technical concerns, one heritage concern and two energy concerns. It also has the potential for 34 related measures.

London Energy Transformation Initiative (LETI) Guide

LETI is a network of built environment professionals and have produced a detailed Climate Emergency Retrofit Guide to be used by architects, engineers, Local Authorities, social landlords, energy professionals, contractors and homeowners. The guide uses six key principles for best retrofit practice. Whilst it does use the starting points of Whole House Approach, working to balance energy consumption, building health and heritage and occupant health, the LETI guide has a fabric first approach and sets out energy targets for the retrofit.

The free guidance document provides best practice approaches and design details for all elements, along with case studies for how to achieve retrofit.

Page updated: 2/11/2022

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