Green Tau: issue 15

3rd September 2021 – revised 11th January 2023

Heating homes without carbon?

Domestic energy use, ie for heating, lighting and electrical appliances, generates around 22% of the UK’s carbon footprint. The majority of that 22% comes from heating our homes. This is not surprising when you consider that 90% of homes are heated using gas boilers. Gas, one of the main fossil fuels, is burnt to heat water to warm our homes. As it burns, carbon dioxide is released. A three bedroom house with a 30KW condensing boiler will, for every hour the boiler is running, will emit around 7kg of CO2 or over the course of year around 3.65 tonnes of CO2.

It is obvious that we cannot continue to heat our homes using gas (or oil or coal) if we are to prevent the catastrophic rise in global temperatures. The Paris Agreement signed by parties at the Paris COP in 2015 set as it goal that participants should reduce carbon emissions so as to keep the rise in mean global temperature to below 2 °C .

In April 2021 the UK’s sixth Carbon Budget set the goal of cutting emissions by 78% by 2035. This time the Budget was set to also include the UK’s share of international aviation and shipping emissions. This revised budget should put us three-quarters of the way to achieving net zero by 2050.

Parties at COP27 in November 2021 agreed that this target should be reduced further to just 1.5 °C. To achieve this target the means by which we heat our homes will have to be radically transformed. 

This can happen in surprising ways. In Islington waste heat from the Northern Line is being soused to heat 1350 homes, a primary school and two leisure centres. In addition the heat is also generating electricity that powers lifts and communal lighting in a nearby tower block. Similar district heating solutions are being developed in other parts of the country too, for example heat  extracted from a flooded coal mine in Durham will heat 1500 homes. 

Both these projects use heat pump technology. This is the most promising solution for drastically reducing carbon emission whether heating a large office block or the average house. A heat pump is a scaled up fridge that works in reverse. Its refrigerant liquid absorbs heat from the air – or the ground – outside the building. This is compressed and transfers inside the building  where it is released as heat via warm air or via warm water (for radiators or underfloor heating). The heat pump is powered by electricity. Heat pumps, in terms of energy used and heat produced, are at least 3 times as efficient as gas boilers. In terms of running costs, the carbon footprint of a heat pump will depend on the source of the electricity it uses. Electricity from a wind farm has a carbon footprint of 10-20g/KWh compared with 450g/KWh for electricity from a gas fired power station. 

The Government’s net zero carbon targets anticipates the installing of 600,000 heat pumps a year by 2028. However in 2021 only 42,779 heat pumps were installed make this target look questionable.

There needs to be an expansion of both the production capacity of heat pump manufacturers and of the number of qualified heat pump installers, as well as improved Government finance to make the switch affordable for everyone.

The other approach to reducing the carbon footprint arising from heating our homes, is to insulate them. The better insulated a property is, the less additional heat is needed to achieve a comfortable level of warmth. Thus less energy is needed and one’s carbon footprint is reduced. A well insulated home also reduces draughts and cold spots which makes spaces feel warmer. 

Home insulation options include:

• cavity wall insulation 
• External wall insulation suitable for buildings with solid walls
• Loft insulation 
• Draught proofing doors and windows 
• Double – or even triple – glazing windows
• Underfloor insulation
• Thermal external doors
• Fully enclosed porches

Information on the potential cost savings of upgrading home insulation plus available grants can be viewed in various websites including https://www.which.co.uk/reviews/home-grants/article/insulation-grants-aGAZv8p9hGkY

NB Relevant information is constantly changing.