Retrofitting has the potential to improve efficiency in the built environment, one of the biggest greenhouse gas emitters, and help cities meet net zero targets.
It is not a new idea, but many people still don’t grasp retrofitting.
There’s a lot of misunderstanding and doubts about its efficacy. Sometimes the idea is so alien to people that they don’t even know how to pronounce it!
So, let’s take a whistle-stop tour to clear up what retrofitting really is and why it’s important.
What is Retrofitting?
The aim of retrofitting is to improve the interior environment for occupants by applying physical or operational alterations to a property.
This may take many forms:
- Hardware – applying cladding to the exterior of a building envelope can trap heat (and fireproof a property); other examples include triple glazing, solar or tankless water heaters, LED lighting (which eliminates wasted heat energy), and insulating wall, floor, and ceiling cavities
- Renewable energy – switching from fossil fuel sources to wind, solar, hydro, and geothermal power
- Smart technology – such as sensors that monitor water use, appliances linked to the Internet of Things, or digital electricity metres that allow residents to see and manage their energy use in real time
- Utility management tools – integrating smart technology with software to better understand and control the consumption of energy via a central dashboard, potentially improving efficiency and minimising waste by integrating and responding to multiple data sources in a single interface
These examples make retrofitting seem quite high-tech, but that’s not exclusive. There are plenty of low-tech alterations that aid temperature regulation and improve quality of the interior and exterior environment, such as adding passive shading (window shutters), greenery, and wall hangings.
Why Retrofit?
Retrofitting is usually done to improve the energy-efficient performance of a property, hence the other term, “home energy retrofit”.
This is because humans use a lot of energy. At home, it powers appliances, cooks our food, heats and pumps water, and helps us to see at night. And let’s not forget how much energy is used in other buildings, like lighting office blocks, powering hospital apparatus, and preventing kids from freezing at school in winter.
Our use of energy is not a problem in itself, but in combination with inefficient buildings, it has wider implications.
According to the World Green Building Council, the build environment is “currently responsible for 39% of global energy related carbon emissions,” making it one of the biggest contributors to climate change – far more than even transport (21%).
Retrofitting would prevent a great deal of these emissions from being released – or produced in the first place.
It is especially needed for older properties that were not built to modern standards and do meet contemporary needs, or where the quality of a building has deteriorated over time. In Europe, it’s thought that 75% of buildings deliver a poor energy performance largely because of their age.
Demolishing buildings and reconstructing them from scratch would be counterproductive, because of the embedded emissions these processes release. Of the building stock we’ll be using in 2050, 80% is already built so we need to commit to improving what’s already there today.
Advantages of Retrofitting
Retrofitting is about improving quality of life, and there are plenty of advantages:
- Improved occupant comfort – much of it to do with regulating room temperatures
- It can improve a building’s lighting capability, water use, soundproofing, and air quality
- Cladding (external insulation) can add a more pleasant looking finish
- Green facades, which help cool the environment and absorb stormwater, take beautification to the next level
- Better energy efficiency & reduce emissions slow climate change
- Ridding a place of damp will ease their residents’ coughs
- Removing large gas boilers will give return more living space
- Sometimes there’s money to be saved
Heat Pumps
Even when people are clueless about retrofitting, many have heard of heat pumps – which can provide cooling as well as heating and are supposedly much better for the environment that air conditioning units.
However, where most of the retrofitting is currently taking place (in the European Union), keeping people toasty is high on the agenda.
In the EU, around 80% of residential energy use is for the purpose of heating our homes. Oil and gas systems are expensive – affected by market fluctuations – and, as fossil fuels, release carbon dioxide, which contributes to climate change.
Insulation, triple glazing, and draught excluders are common modifications, designed to keep cold wind out and warm air in, but a fairly modern alternative to traditional boilers is gaining traction.
Heat pumps extract warmth from the air, water, or ground, amplify it, and then pump it into a property. They’re cheaper to run and depending on who you believe are between three and five times as energy efficient as gas boilers. Increasingly, when residents are due a new boiler, they’re being encouraged to opt for a heat pump.
Some commentators doubt their reliability, but heat pumps tend to outperform other boilers down to a temperature of -30°C and nobody’s questioning refrigerators: the technology effectively works on the same chemical process, but in reverse.
Suitable Buildings
Retrofitting can be applied to almost any building, although preservation orders prevent changing the aesthetics of the protected architecture for historic properties, which presents a clash between the past and future of a city.
Most examples of urban retrofitting are seen on low-rise residential properties, but city administrations are increasingly retrofitting blocks of flats and public buildings. Due to their size and flat roofs, we’re frequently seeing council offices, social housing, schools, and hospitals as sites for laying solar panels.
Assessing What’s Needed
There is no such thing as a one-size-fits-all retrofit. Each building presents its own conditions, from the way it’s built to wear and tear over time, and alterations it’s undergone over the years.
Before any retrofitting takes place, each property should be individually assessed to ascertain what would and would not work.
Shallow & Deep Retrofits
It’s possible to make a handful or individual changes to a property, or a comprehensive overhaul. These are, respectively, known as a shallow and a deep retrofit.
Each has its advantage: the piecemeal work of shallow retrofits is more affordable, causes less disruption to occupants, and in many cases prioritises a shift to renewable energy sources. But one alteration may counteract with another implemented later on if they’re not planned as part of a comprehensive single project. For example, sealing the building envelope will stop heat escaping but if triple glazing is added later without thoughts on breathability, it could lead to condensation.
A deep retrofit done well will consider the full picture, so the outcome will be better: a whole-house renovation can achieve an almost 100% efficiency rating, like a passive house, but costs can be in the tens of thousands, and residents usually have to move out while the work is underway.
Common Challenges
Because of the complexity involved, rates of retrofitting remain relatively low. It doesn’t help that it’s not an exciting topic, so it can be difficult to engage individuals, which is the necessary first step. Energy Team in Dunleer, Ireland, have tapped into an effective use of gamification, hosting fun quizzes that inform people about retrofitting basics without them even realising.
Ventilation
Old, unrenovated properties commonly have cracks and gaps in walls, warped and ill-fitting window frames, insufficient insulation, and doorways that allow draughts in and heat to seep out.
In worst case scenarios, turning the heating on or up costs us money but provides limited benefit. Some building materials – like steel – are cold, so suck heat out of the room.
Being costly and uncomfortable to live with, sealing building envelopes to retain heat becomes a retrofitting priority (at least, in colder climates). In the process, all too often ventilation gets overlooked.
Airtight homes might be good for retaining energy, but liveable homes require fresh air, which means the best buildings are breathable.
Ignoring this can have real health implications: as condensation forms, it may cause damp and mould to form, which can lead to respiratory illness. Homeowners, landlords, housing associations, and cities responsible for social housing tenants need to take these issues seriously.
And All the Rest
There are other challenges too, which frustrate the speed of the home energy renovation wave:
- major up-front expense, alienating low-income households most
- the prospect of mess
- not knowing where to find trustworthy and experienced technicians
- to save hassle, we stick with what is familiar if it already works
- confusing subsidy application processes
- mis- or disinformation that undermines the value of retrofitting
- too little commitment from political leaders
All too often, the promise of return on investment is relied upon to convince people to retrofit, but it is not as persuasive as advocates like to believe.
Sure, improved energy efficiency makes utility bills less expensive, and over time these savings will equal the cost of the renovation, after which it’s cash in pocket. But that can take up to 25 years and people tend not to think that long-term.
Successes So Far
Scaling efforts have much more potential with cities at the helm.
Most of the time, it requires municipalities to organise the work and foot the bill. Significant inroads have been made by Edinburgh, Scotland, for example, where the city council has pushed ahead with a programme of mass retrofitting social housing. The problem is that the scheme falls short for private homeowners.
Oxford, also in the UK, has upped efforts to decarbonise building stock, first via the council showcasing heat pumps as an example for the public, and later thanks to an independent NGO acting as facilitator for discussions between local stakeholders to share their own ideas on triggering change.
And Germany‘s national Heat Pump Week, based on a communication strategy developed for Hannover, triggered a threefold increase nationally in applications for heat pump subsidies. Although only accounting for 7% of households, there were already 2 million heat pumps active in German homes in 2024, and they now account for 42% of all heating system installations throughout the country.
Prepare for the Revolution!
Even if retrofitting doesn’t offer much ROI, there’s good money to be made from the retrofitting revolution.
As it continues to take hold, we’ll need more and more competent and trustworthy technicians to meet demand.
As an emerging market where competition it limited, those who trained ahead will be able to name their price. Expert solar panel installers can expect to take home $84,000 annually!
This isn’t speculation: the Irish Times reported a national retrofit programme would create in excess of 30,000 jobs and generate “€4.5 billion in extra disposable income for citizens” in the Republic of Ireland alone.
Clearly, there are many convincing reasons we should be putting more emphasis on retrofitting. These arguments have fallen a long way from the decarbonisation narrative. No matter: as long as that’s still the outcome, whether we draw attention to it or not, retrofitting has achieved what we need it to.