Households in the UK have cut their carbon emissions by around 2.4 million tonnes since 2005 thanks to the take-up of high-energy condensing boilers, new research has shown.According to H&V News, research carried out by Valiant Group indicated that building regulations put into place three years ago have prevented the level of emissions from domestic heating systems from rising over one million tonnes.The research claimed UK households could make a further carbon cutback if all cast iron boilers over 15 years old were replaced by more energy-efficient models.It also claimed that up to 150,000 tonnes of carbon emissions could be saved annually if ten per cent of the planned three million new homes to be constructed in the UK by 2020 install a solar hot water system or heat pump."We estimate there are around four million old, inefficient boilers still installed and operating in UK homes," said Jim Moore, UK managing director of Valiant Group."The government should make a concerted effort to incentivise householders to replace these," he added.According to the Manchester Evening News, installing an energy-efficient boiler could represent a savings of around £150 per hear on heating bills for the average UK household.