Zero Carbon in Buildings

Zero Carbon in Buildings


Net Zero in Housing:

Whichever target date you support, Extinction Rebellion’s 2025 or Theresa May’s 2050, it’s clear we’re not going to achieve net zero greenhouse gas emissions without big changes to our homes.  And if we live, as many of us do, in solid wall houses built in an age of coal, the challenge is magnified.

The built environment (including much needed new build for our growing population) is responsible for 42% of all UK greenhouse gas emissions, with housing approximately half of that.

Heating our homes is the biggest polluter, at 10% of emissions, a household average of 2.7 tonnes a year.  And that gas combi boiler hanging on our kitchen wall is the biggest culprit.

Emissions from the residential sector have reduced by a relatively low 16% since 1990 compared with an overall reduction of 43.5%, though that does include a quarter new homes.  Most of that residential reduction has come from the steady decarbonisation of electricity supply with the virtual elimination of coal and the growth of renewables, the one great UK success story in the fight against climate change. Grid electricity is now cleaner than gas, and still has a way to go as more and more zero carbon capacity comes on stream.

Alternatives to natural gas

So what can we do?  Let’s look at alternatives to natural gas.  Some could come from district heating schemes powered by biomass or, in a few parts of the country, by geothermal energy.  The bulk, however, has to come from the two options of renewably produced hydrogen and decarbonised electricity.  The conversion of the gas grid to hydrogen and the changes to 23 million sets of internal pipework and appliances is a logistically complex infrastructure upgrade comparable to the transition from town to natural gas in the 1960s, not to mention the additional requirement of creating a huge hydrogen supply industry from scratch.

The government, in its consultation document on The Future Homes Standard, concedes that hydrogen ‘may have a role to play in heating systems of the future’ (page 19), but is clearly planning for the second option of decarbonised electricity, with homes built from 2025 completely disconnected from the gas grid.

Direct electric heating is very straightforward, though much more expensive to run than gas. The best electric option is the heat pump.  These work like fridges in reverse and extract heat from the air, the ground or water into the building.  If your building is already well insulated, you can run your heating system solely at night on an off-peak electricity tariff.   This is how the Ullet Road Eco Offices manages to bring its heating cost to below the price of gas.  Its Air Source heat pump consumes renewable electricity from Good Energy at a night rate of 11.3p/kwh.  Over the winter months, it generates 3kwh of heat for each 1kwh of electricity, bringing the price per unit of heat down to a third of the electricity cost, or 3.76p, below the Good Energy gas price of 4.3p.

Performance at the Eco Offices during Spring and Autumn, when it is used intermittently is not as good, and this is currently being investigated. Selecting and configuring the right type of Heat Pump system is not as straightforward as installing a gas boiler, and a whole building approach together with independent expertise may be required.

However, as heat pumps become the norm, costs will fall, and standard solutions will develop for the different types of houses.

Generating our own renewable heat and power

Unfortunately, the abrupt terminations of a number of green energy schemes since 2015, without adequate and timely replacement, decimated the nascent residential solar industry, and the spread of domestic solar PV and solar thermal has stalled.

There are, however, grounds for optimism.  Installation costs have plummeted, battery technology has advanced and a number of installers known to us have managed to survive through diversification. The likely inclusion of PV for new homes in the Future Homes Standard from 2020 will provide a steady market for them too.

And the re-instatement of an export tariff may well stimulate interest from existing householders.

Insulation, Air tightness and Heat Recovery

Again, these have been affected by government cuts and confusion. Many residents have, however, successfully installed internal and external wall, sub-floor and loft insulation, as well as upgrading windows and doors for air-tightness and double or triple glazing. A smaller number have installed continuous ventilation with heat recovery, especially useful in kitchens and other damp areas. Waste water heat recovery has been mandated for new homes from 2020 under the Future Homes Standard.

Low carbon building standards for new build are on the way

The Ministry of Housing, Communities and Local Government has published a consultation document on the Future Homes Standard for new homes announced in the Chancellor’s 2019 Spring statement.  They have asked for responses from developers, builders and other construction professionals, property owners and occupiers as well as environmental groups and local authorities by the 10th of January 2020.

They are proposing a 20-31% improvement on building performance compared with the current 2013 building regulations by 2020 and 75-80% by 2025, when all heating systems in new homes will have to be non-fossil fuel.  These are interim solutions only toward the goal of zero net emissions from the building sector by 2050.

They have proposed two options for 2020:

  • a 20% reduction based on fabric alone – air tightness measures, triple glazing and waste water heat recovery, and
  • a 31% reduction for houses and 20% for flats using slightly less stringent fabric measures, plus ‘technologies’’ like solar PV.

Both proposed 2020 standards are still based on the use of gas boilers.

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