It is estimated that the global construction industry uses 40% of the world's energy supply and that around 15% of Scotland's carbon emissions are related to the way we heat our homes.

While recognising the need to increase the supply of new homes across the country, the Scottish Government's Housing to 2040 vision for the nation's homes and communities, challenges the housebuilding industry to contribute to tackling climate change and achieving net zero carbon emissions by 2045 by ensuring that those homes are energy-efficient, use zero emissions heating and are adapted to our future climate and meet the needs of people who live in them.

But it's not just new homes that will be affected. Existing homes are to be retrofitted to improve their energy efficiency and decarbonise their heating systems to make fuel poverty a thing of the past. Given that there were 2.62 million homes in Scotland in 2018 and fewer than 22,000 new homes are constructed each year, to have any chance of achieving the desired net zero carbon emissions target, it isn't just housebuilders or indeed the construction industry who need to make changes; tenants, landlords and individual homeowners will also have to take action.

Climate change awareness has risen dramatically in recent years and COVID-19 has heightened awareness of certain sustainability themes. The Scottish Government has, however, been investing in sustainable housing and communities since 2007, including the Carbon Emission Reduction Target focused on home insulation programmes, and the Scottish Sustainable Communities Initiative in 2008 which sought to transform the design, quality and environmental standards of new housing-led developments, such as Grandhome in Aberdeen. "Homes that don't cost the earth" in 2012 was the prelude to Scotland's Sustainable Housing Strategy which was published in 2013 .

So what is sustainable housing? The term encapsulates many different aspects of housebuilding, but in its widest sense can perhaps be regarded as housing which puts environmental concerns at the heart of design. But sustainability starts long before houses are designed and constructed. Planning policies contain a brownfield first approach to new development. Building on previously developed or "brownfield" sites has fewer environmental impacts than building on undeveloped or "greenfield" sites. And as brownfield sites are generally found within existing built-up areas, they benefit from proximity to existing facilities, such as schools, shops and public transport, thus cutting down the need to use, or even have, private cars. Utilities will already be in place.

Making efficient use of land is another principle of sustainable development. There is a return to higher density mixed use developments as not only does this reduce the amount of land required, it also means that facilities – shops, schools, employment, open space – will be within walking distance. Developments built around the 20-minute neighbourhood, such as Chapelton and Countesswells, are less car-dependent and have health, sociability and community benefits as well as reducing carbon emissions.

New regulations are being brought forward which will require all new homes consented from 2024 to use zero direct emissions heating. Zero or very near zero emissions heating in existing homes will be required between 2025 and 2045.

Alternatives to gas central heating include heat pumps; district heating networks; hydrogen boilers; and electric radiators.

Heat pumps absorb natural heat which can then be used to warm homes and water. The three main types are: ground-source; air-to-water; and air-to air. They are installed individually in houses. Heat networks supply heat from a central source, such as a combined heat and power plant and distribute it through underground pipes. There is no need for boilers within each property. They are most effective in high density developments.

The Scottish Government and Scottish Green Party's Shared Policy Programme for this parliamentary session proposes investing at least £400M in heat and energy efficiency projects, including support for zero carbon local and district heat networks, including large scale heat pumps.

The Aberdeen City CHP Network currently provides energy efficient, low cost, low carbon heating in 33 multi-storey blocks, 2 sheltered housing blocks as well as 15 public buildings in the city. The NESS Energy from Waste Project which is due to be operational in 2022 will be connected to a district heat network in East Tullos which will heat homes in the Torry area.

Hydrogen boilers heat the home with both natural gas and pure hydrogen. Existing gas boilers can be converted to hydrogen use. The Aberdeen Hydrogen First Initiative at the Cloverhill development in Bridge of Don will include a pilot scheme incorporating micro-CHP fuel-cell technology into 30 homes.

2.2 million homes in the UK already use electric radiators and smart controls make them an efficient way to control heat requirements and thus reduce energy bills. They are currently perhaps the most likely replacement for gas boilers in existing houses.

Modernising construction of housing is also key to achieving the energy efficiency standards needed to meet the country's net zero targets. The Advanced Industrialised Methods for Construction of Homes Project (which includes north east housebuilders, Stewart Milne Homes and Barratt) has been developing the use of panelised offsite systems tol enable a house to be constructed on-site quicker and cheaper than traditional masonry methods, with improved build quality and reduction in waste.

These and other sustainable measures may save the planet, but they come at a cost to housebuilders and homebuyers. A heat pump costs approximately £5000 more than a gas boiler, yet surveys show that homebuyers are only willing to pay an extra £3000 to have green technologies in their home. The Scottish Government is therefore looking at cash-back and grant schemes for home and building owners who install zero emission heat improvements in their properties.

'This article was originally published in the Press and Journal, September 2021'