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.
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.
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 WC's, 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.
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 Wiki
- Allowable solutions.
- Bill Gething and Katie Puckett - Design for Climate Change.
- Bonfield Review.
- Building engineering physics.
- Climate Change Act.
- Design for deconstruction.
- Earth building.
- Eco towns.
- Ecobuild 2016 - Making the business case for large scale retrofit investment.
- Energy efficiency of traditional buildings.
- Energy Performance Certificates.
- Fabric first.
- How to deal with retrofit risks.
- National Refurbishment Centre.
- New energy retrofit concept: 'renovation trains' for mass housing.
- Performance gap.
- Renovation v refurbishment v retrofit.
- Retrofit coordinator.
- Retrofit, refurbishment and the growth of connected HVAC technology.
- The Each Home Counts report and traditional buildings.
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