Rethinking retrofit: how to secure a low-carbon future without sacrificing air quality

Insulating the UK’s housing stock is a crucial component of the nation’s net zero ambitions, but we risk doing more damage to the environment and the air we breathe unless we rethink how we retrofit, discovers Chloe Coules.

Retrofitting the 29 million existing homes in the UK plays a significant role in the government’s plans to achieve net zero by 2050, with energy use in homes accounting for around 14% of UK greenhouse gas emissions according to the Committee on Climate Change.

The benefits of retrofitting are indisputable – better insulation means that we need to use less energy to heat our homes, helping to cut our carbon emissions and electricity bills.

However, there is concern from indoor air quality experts that the way we are insulating our houses is causing more damage to the environment and risks leaving residents exposed to dangerous pollutants.

Architect and environmental consultant, Tom Woolley, explains that there is an assumption within the construction sector that you can use any insulation any way you like without incurring risk, but he argues that leaves homeowners in a disastrous situation.

He is concerned by the recent waves of protests calling for mass insulation in the UK without stipulating what kind of materials should be used: ‘You cannot just call for buildings to be insulated, you have to say they have to be insulated properly, otherwise you could be making the situation worse.’

But why can insulation be bad news for our indoor environments, and how can we reach net zero without putting our health in danger?

Hazardous homes

Synthetic insulation is the most common product used to improve a home’s energy efficiency in the UK, but it can be a dangerous source of hazardous emissions.

Most people know the risks of asbestos, a type of insulation that is now illegal in Europe and still leads to 13 deaths in the UK every day, but what they don’t know is that most of the market-leading synthetic insulations can also pose serious risks for our health.

Mineral and glass fibre insulation, commonly known as glass wool, contains fibres, adhesives, resins and additives that can reduce indoor air quality when released, leading to a range of health issues including irritation of the eyes, nose and throat, rash and itchiness, stomach irritation, worsening of asthma, bronchitis and even cancer.

Polyurethane spray foam insulation, which is widely used in the UK, has led to serious health complaints including respiratory and breathing issues, skin irritation and neurological issues in the US.

Most foam insulations are also synthesised using hazardous chemicals, which have a negative impact on the environment and air during manufacture, use and disposal. They contain a range of chemicals that can emit volatile organic compounds (VOCs) and carcinogens, such as petrochemicals, solvents and flame retardants.

Through the combination of chemicals found in synthetic insulation and increased airtightness created during installation, retrofitting can therefore lead to an increase in the level of VOCs in the indoor environment.

Researchers at the University of Exeter found an increase in reported asthma problems when houses had been renovated to make them more energy efficient, which they concluded was most likely due to an increase in VOCs. This is supported by other studies that have found VOC emissions on indoor air quality tests when there is no other possible source other than synthetic insulation.

This is concerning as VOCs are one of the biggest hazards to indoor air quality, leading to a range of health issues including irritation, headaches, dizziness, loss of coordination, nausea and visual disorders, and allergic reactions including asthma during acute exposure, as well as damage to vital organs after chronic exposure, even causing cancer in some cases.

No breathing room

Builders often assume that making a house as airtight as possible is the best way to make it energy efficient, but this can cause a range of issues, including higher radon levels and overheating.

Various studies have linked retrofitting with increases in radon levels, for example researchers studying over 3000 houses in France concluded that thermal retrofit could increase the indoor radon concentration significantly.

A study in Belgium also found radon levels of 750 Bg/m3 in a passive house in a low radon risk area, this is dangerously above the UK’s safe limit of 200 Bg/m3.

Radon is a highly dangerous pollutant and is recognised by the World Health Organisation as the second most important cause of lung cancer after smoking, leading to over 1,100 deaths a year from lung cancer.

A team of researchers led by James Milner from the London School of Hygiene and Tropical Medicine concluded that: ‘Unless specific remediation is used, reducing the ventilation of dwellings will improve energy efficiency only at the expense of population wide adverse impact on indoor exposure to radon and risk of lung cancer.’

Tom Woolley also explains that using synthetic insulation to increase energy efficiency and airtightness can lead to problems with overheating: ‘One of the problems which affects indoor air quality, particularly in the South of England, is overheating. There’s a lot of literature about this now where people are coming home and finding their houses incredibly hot inside and finding it really difficult to keep them cool, particularly during really hot weather, and that’s because these lightweight synthetic insulation materials have no thermal mass, so they have no way of preventing overheating or keeping the house cool.’

Building badly

The negative impact of insulating materials on indoor air quality can be made worse by poor installation, exposing people to unnecessary risks and more air quality issues.

Tom Woolley explains that modern methods of building can place occupants at greater exposure to air pollution: ‘In the past, insulation, even if it was pretty horrible, hazardous stuff, was generally contained within two leaves of masonry within the cavity, and the emissions from that would not be significant. But these days, most buildings are timber frame construction, and the insulation is on the inside, so therefore any potential emissions from the insulation are considerably higher than they would have been in the past.’

He adds that insulation is often only separated from the indoor environment by a sheet of plasterboard, which chemical emissions can easily pass through, and actually contains a number of hazardous chemicals itself which are emitted into the air.

Poor installation can also lead to severe damp and mould issues, which are endemic in many buildings in the UK, with over two thirds of people complaining about condensation or mould problems in their homes according to a survey commissioned by the Energy Saving Trust.

Mould exposure is linked to respiratory issues such as an increase in asthma and respiratory infections, with children especially at risk.

Cavity wall insulation is especially problematic for damp and mould, with 3 million houses in England claimed to be affected by badly installed cavity wall insulation, leading to the issue being debated in parliament in 2014.

Tom Wooley explains that a lot of synthetic insulations are not able to cope with dampness, so you get condensation and damp building up within the framework of buildings, making the insulation wet and mouldy.

Despite this, Tom expresses concern that we are moving from one bad insulation solution to another without considering the risks and better ways of retrofitting: ‘There are massive failures and problems with cavity wall insulation, so they started doing external wall insulation and that’s been a disaster, so now they are moving more and more towards internal wall insulation using chemical insulation, and that is potentially even worse because it traps the interstitial condensation and that builds up into mould growth, which very often you can’t see because it’s behind the insulation.’

Natural solutions

The good news is that natural insulation alternatives are available, and they come with a range of benefits that synthetic insulation cannot provide.

Tom Woolley highlights the role that natural insulation solutions, such as sheep wool and hempcrete, can play in addressing the climate emergency: ‘If we want to save the planet, we have to reduce pollution and CO2 emissions. The production of petrochemical and synthetic insulation materials uses a lot of energy, so that’s bad for the planet quite apart from being bad for our health, whereas if you are using low impact materials, they don’t give off any energy in production, so they’re much better. Remarkably, some of the natural insulation materials are even much more thermally efficient than the synthetic insulations.’

Natural insulation materials do not release hazardous emissions, and they may also help to improve air quality, with materials like sheep wool able to absorb formaldehyde.

They are also often hygroscopic, which means they can manage moisture and humidity in buildings, reducing the risk of mould growth and its associated health effects, and they have greater thermal mass so are able to keep buildings cool and prevent overheating.

Tom Wooley also believes that local solutions are the key to deliver safe and effective retrofitting, providing a more holistic and individualised approach to insulating a home.

An example of this is People Powered Retrofit, a householder-led approach to domestic energy efficiency retrofit in Greater Manchester run by Carbon Co-op.

Lewis Sharman, a retrofit adviser at People Powered Retrofit, explains that the organisation always ensures that clients understand the health implications of different materials choices so they can make informed choices, advocating for natural solutions and proper ventilation to reduce the impact of retrofitting on air quality.

However, he says that more needs to be done in central government to develop a nationwide retrofit programme, especially in the wake of the new heat pump grants, which could see energy prices soar for homeowners unless houses are sufficiently retrofitted: ‘The government should be doing more to promote retrofit as a whole, but especially retrofitting properly which would include having a suitable ventilation strategy and measures installed alongside other work.’

This article first appeared in the November Air Quality News Magazine, click here to view.