Retrofitting means 'providing something with a component or feature not fitted during manufacture or adding something that it did not have when first constructed' (Ref: Retrofit 2050: Critical challenges for urban transitions). It is often used in relation to the installation of new building systems, such as heating systems, but it might also refer to the fabric of a building, for example, retrofitting insulation or double glazing. For more information see: Definitions of retrofitting.
Retrofitting has come to prominence in recent years as part of the drive to make buildings more thermal efficient and sustainable. This can help cut carbon emissions, make it cheaper and easier to run buildings, and can contribute to overcoming poor ventilation and damp problems, therefore improving the health of occupants. It can also can increase building adaptability, durability and resiliency and therefore contributes to achieving a circular economy.
The Climate Change Act established a target for the UK to reduce its emissions by at least 80% from 1990 levels by 2050. Since 47% of the UK's carbon emissions are generated or influenced by the construction industry, and it is thought that around 2/3rds of the housing we will occupy in 2050 has already been built, retrofitting is vital.
The 2014 study New energy retrofit concept: 'renovation trains' for mass housing', by Ronald Rovers, estimated that 40 million houses in the EU would have to be retrofitted by 2020 if carbon emissions reductions were to stay on track. This, he argued, would require the adoption of mass retrofit techniques, some of which have been piloted in in the Netherlands.
 Retrofit techniques
Retrofitting in this context should involve applying an integrated, whole-building process, however, there are a number of basic techniques that can be used for key elements of a building:
- Walls: Cavity wall insulation, internal or external insulation, and cladding of external and internal surfaces.
- Roofs: Insulation and ventilation systems.
- Doors: Draught proofing or replacement high-performance doors.
- Windows: Installation of double or triple glazing, draught proofing of existing glazing.
- Floors: Installation of insulation.
- Tanks and pipes: Lagging.
- Lighting: New controls, occupancy sensors, Light-Emitting Diode (LED) lighting and other low energy technologies.
- Boilers: Installation of high-efficiency condensing boilers or micro CHP, new controls, connection to low carbon community heating systems.
- Chiller plant improvements: Plant, pumps, piping and controls upgrade.
- Controls: Installation of smart controls and building management systems.
- Air conditioning: Upgrade, or replace with air or ground source heat pumps or passive cooling.
- Renewable energy systems: Installation of photovoltaics, solar thermal heating, passive solar heating, wind energy, wood and organic waste power sourced heating or power plant, micro-hydro power, and so on.
- Water conservation: Installation of low-flow equipment such as water fittings, shower heads, dual flush WCs, rainwater harvesting, and so on.
- Electricity: Peak saving through thermal energy storage, onsite electricity generation, combined heat and power, and so on.
- Advanced metering systems: Smart meters.
 Retrofit in practice
The process of retrofitting involves the careful balancing of different elements and their effects on the overall performance of a building. A change in one part of a building can affect another, and sometimes this is only apparent after irreversible defects have occurred. For example:
- Sealing buildings to improve their air-tightness can cause condensation problems.
- Insulating a roof without also ventilating it can the cause decay of timber structure.
- Internal wall insulation will remove the benefits of thermal mass which may have a detrimental effect on fuel usage.
- External wall insulation will prevent the thermal store of heat from solar gain to be utilised within the building.
- Poorly installed cavity wall insulation can create cold spots that then have damp problems that are extremely difficult to rectify.
- Pre-existing problems can be covered up, and so more difficult to diagnose and rectify.
Some of the most common problems facing retrofit include: under-ventilation, condensation, air leakage, mould issues, rising damp, interstitial condensation, and overheating.
It is very important therefore that these and other risks are understood and managed in a way that is appropriate to each individual project. Standard solutions should not simply be rolled out without proper consideration, and it is vital that care is taken to ensure high quality installation. At each of the four retrofit processes – assessment, design, installation and operation – it is advisable to have 'retrofit watch points' to help avoid problems such as:
- Poor management of trades.
- Poor integration of trades.
- The adoption of inappropriate solutions.
- Overambitious performance gains claimed by designers and suppliers.
- A lack of robustness of detailed design.
- Fragmented procurement and delivery (lack of overall responsibility and ownership).
- Poor construction sequencing and commissioning.
- Inadequate handover and user guidance.
Once a building has been retrofitted, the process of post-occupancy evaluation is important in determining its overall success and ensuring that lessons are learned for future projects. This can be involve monitoring fuel use, occupant surveys, air permeability testing, and thermographic surveys and so on.
 Related articles on Designing Buildings
- Alteration work.
- Bill Gething and Katie Puckett - Design for Climate Change.
- Bonfield Review.
- CIOB Ireland responds to Budget 2022.
- Definitions of retrofitting.
- Ecobuild 2016 - Making the business case for large scale retrofit investment.
- Energy efficiency of traditional buildings.
- Energy efficiency retrofit training videos.
- Energy Performance Certificates.
- Fabric first.
- Government urged to include home energy retrofits in Industrial Strategy.
- Home Energy Masterplan.
- Households Declare.
- How to deal with retrofit risks.
- IHBC COP26 podcasts.
- IHBC responds to Energy Company Obligation ECO4 and PAS 2035.
- LETI publishes Climate Emergency Retrofit Guide.
- National Refurbishment Centre.
- National Retrofit Strategy NRS.
- New energy retrofit concept: 'renovation trains' for mass housing.
- PAS 2035.
- PAS 2038:2021 Retrofitting non-domestic buildings for improved energy efficiency.
- Renovation v refurbishment v retrofit.
- Retrofit and traditional approaches to comfort.
- Retrofit coordinator.
- Retrofit, refurbishment and the growth of connected HVAC technology.
- Retrofitting solar shading.
- Shallow retrofit.
- Step-by-step retrofit.
- The Each Home Counts report and traditional buildings.
- Whole house approach.
- Whole house retrofit plan.
 Useful external links
About the wiki
Anyone is welcome to use and contribute to the wiki in different ways.
 Engaging with the wiki
- Contribute to existing articles
- Create articles
- Share articles through social media and other channels
- Contact the CIRCuIT project to let us know what you think and how we can improve
 Add your own content
To contribute to or create an article, you can follow these steps:
- Register as a user
- Read through the editorial policy and guidance on writing and contributing to articles
- See the detailed help page on tips on writing wiki articles
- Try editing a test article
- If editing an article, select 'Edit this article' underneath the article title
- If creating a new article, select 'Create an article'. In the 'Select categories' area, expand the 'Industry context' list and tag 'Circular economy' to add your article to this wiki
 Who is this wiki for?
The articles contain information on implementing circular economy approaches in construction that could be relevant to:
- Construction contractors
- Developers, owners, investors
- Manufacturers and supplier
- Universities and research
- Urban planners
 About CIRCuIT
The Circular Economy wiki is supported by the Circular Construction in Regenerative Cities (CIRCuIT) project, which is funded by the European Union's Horizon 2020 research and innovation programme. CIRCuIT is a collaborative project involving 31 ambitious partners across the entire built environment chain in Copenhagen, Hamburg, Helsinki Region and Greater London. Through a series of demonstrations, case studies, events and dissemination activities, the project will showcase how circular construction practices can be scaled and replicated across Europe to enable sustainable building in cities and the transition to a circular economy on a wider scale.