House owners in Scotland will face barriers to selling their homes unless they switch from fossil fuel-powered boilers to greener methods under plans being considered by the SNP-Green alliance.
Boilers in millions of properties may be denied the official energy rating required to avoid replacement by alternative power sources, such as electricity-driven heat pumps.
It could mean the change to greener alternatives would have to be made before houses are put on the market.
The plans are part of a transition away from fossil fuels, such as gas and oil, which is necessary for the Scottish government to meet targets aimed at reducing the impact of climate change.
Ministers have pledged to cut 1990 levels of carbon emissions by 75 per cent in seven