Green Tau: issue 15

Varodrig took this photo from the Ula platformFirst – gas from the Oselvar module burns on the flare of the BP Ula oil platform in the North Sea on April 14th, 2012

3rd September 2021

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 , and preferably no more than 1.5 °C. To achieve this Theresa May announced in June 2019 that the UK would set itself the target of cutting its carbon emissions to net zero by 2050. To achieve this Government 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 this target will be hard to meet unless there is an that expansion of both the production capacity of heat pump manufacturers and of the number of qualified heat pump installers.

Surprisingly the cost per KWh for gas is less than that of electricity –  this can impact on the cost of running a heat pump. Part of the higher cost of electricity is due to the government’s carbon tax designed to fund renewable energy developments. Whilst this tax is levied on electricity it is not levied on gas!  

If you would like to petition the government to reverse this situation go to https://petition.parliament.uk/petitions/588159/signatures/new

To some extent the cost of running a heat pump can be subsidised by applying for the Renewal Heat Incentive scheme. This makes payments according to how much heat you generate via a renewable source such as a heat pump, but as they say, ‘conditions apply’.

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

Some grants are available for low income households to improve the insulation of their homes through the Energy Company Obligation scheme. Further information can be found here: https://warmauk.com/blog/who-qualifies-for-the-free-insulation-grant/

However the Government’s Green Homes Grant that would have seen an upgrading of the insulation of 600,000 homes has been cancelled. 

Next week’s Eco Tips will feature ways of keeping warm at home.

Author: Judith Russenberger

Environmentalist and theologian, with husband and three grown up children plus one cat, living in London SW14. I enjoy running and drinking coffee - ideally with a friend or a book.

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