The Code for Sustainable Homes is intended to cover all possible sources of carbon dioxide (and other gases which cause even more global warming) during building and using the house. Level 5 ensures that heating and lighting the home don’t contribute to global warming; Level 6 covers cooking and domestic appliances like fridges and washing machines too.

The first principle is to make everything in the house as energy-efficient as possible, so no energy is wasted. The second principle is to use the energy of the sun in various ways. The third principle is to reduce to a minimum the amount of energy used in building the property.

Measures used to meet the zero carbon standard in this house include:
- super insulation of walls, roof, doors and windows
- airtight construction (warm air seeps through ordinary walls)
- heat exchanging ventilation (warm the fresh air coming into the house using the stale air going out)
- making the most of daylight
- making the most of the warmth of the sun to warm the house
- storing the sun’s heat in the walls and a special water tank
- using “solar thermal” panels on the roof to heat water
- using “photovoltaic” panels on the roof to generate electricity. Some of this is used in the house – some is exported to the national grid, to compensate for the electricity which is imported when there is not enough sunlight. (The imported electricity comes from a wind farm, but this does not count for the Code because a future owner could change this.)
- using the most efficient electrical appliances available
- growing firewood in the garden to burn in a wood burning stove in the house. Because of all the other measures, one stove is enough for the whole house, and will only be needed on the coldest six weeks of the year. As the trees grow back, they re-absorb from the atmosphere the same amount of CO2 as the chimney emits.

The Energy Saving Trust has a more technical explanation of how Levels 5 and 6 can be applied in this PDF , and there’s a great deal squeezed into one page at greenspec.co.uk.

Zero-carbon definition abandoned

In March 2011 the UK Government short-sightedly abandoned the recognised definition of zero-carbon homes (net zero-carbon emissions over the course of a year) that the industry has been working to, and for which there was broad backing from across the sector. While there will still be a so-called zero-carbon requirement, it will no longer apply to all energy used.
Heating, lighting, hot water and building services, are measured; but built-in electrical appliances (eg hobs, ovens, washing machines) and all electrical equipment that is plugged in (eg computers, TVs, supplementary heaters, etc) are all ignored. The plans were detailed in the Plan for Growth published at the time of the March budget. http://www.hm-treasury.gov.uk/ukecon_growth_index.htm

See

http://www.melstarrs.com/elemental/2011/03/27/the-zero-carbon-homes-debacle/

http://www.wwf.org.uk/wwf_articles.cfm?unewsid=4799

http://www.guardian.co.uk/uk/2011/mar/23/budget-2011-zero-carbon-homes

http://www.insidehousing.co.uk/greenest-government-ever-under-threat/6514206.article

http://www.insidehousing.co.uk/news/regeneration/wwf-quits-zero-carbon-task-group/6514363.article

Despite this very disappointing development, the Birmingham zero carbon house has been built to true zero carbon standards. All the energy used in the home is net zero carbon, and in the first year of operation 147% of its energy needs were met by the on-site renewable energy. So in effect it is not just zero carbon, but carbon negative. It can be done. It has been done. It works!

This UK Government code sets standards for energy and water use, and assesses nine areas of sustainability:

• Carbon dioxide emissions, and energy use
• Water use (including the use of rainwater)
• Materials (including their “embedded energy”)
• Surface water run-off (should be minimised)
• Waste (including facilities to make recycling easy)
• Pollution (including pollution from insulating materials)
• Health and well-being (including good use of daylight)
• Management (including the process of construction)
• Ecology (including preserving wildlife)

A Level 6 home is highly sustainable, and over the course of a year, the net carbon emissions are zero. From 2016 all new homes should be built to this standard.

More details can be found at www.communities.gov.uk. There is a new website at www.zerocarbonhub.org, “established to make Zero Carbon homes a reality from 2016. ”

These key features have been suggested for Level 6 (see www.greenspec.co.uk)

Key features

• Excellent levels of insulation.
• Minimal thermal bridges.
• Advanced windows.
• Excellent levels of airtightness.
• Effective orientation for winter solar gains and summer cooling.
• Mechanical ventilation with heat recovery and very efficient in its use of electricity.
• Space and water heating normally from a large solar heating system supplemented by a low-powered gas, oil or LPG fired condensing boiler.
• Lighting by high-efficiency fluorescent lamps.
• Electrical appliances normally A+ rated or better.
• Sufficient on-site electricity generation from renewables to offset the electricity used for lighting, appliances and ventilation.
• A guidebook to explain to users how/why the building differs from normal.