What does “zero carbon” mean?

Chris Duggan — Sat, 11 Apr 2009 10:05:55 +0000

An explanation of the thinking behind the Code for Sustainable Homes

Burning oil, petrol, gas or coal to build houses, heat our homes or generate electricity produces carbon dioxide (CO2). The increasing amount of CO2 in the atmosphere is causing global warming, rising sea levels, extinction and more unpredictable weather patterns across the world. A “zero carbon” or “carbon neutral” building uses a whole variety of methods to ensure that it does not increase the amount of CO2 in the atmosphere.

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.

Energy design summary

Chris Duggan — Tue, 13 Jan 2009 11:08:26 +0000

Quick notes on the ways the design avoids the use of fossil-fuel energy

Thermal insulation: the new roof and walls will be 20 times better insulated than the existing ones.
Airtightness: sealed to a level 28 times better than existing, but retaining vapour permeability to stop condensation. This includes using a special membrane in the walls. Research shows that limiting warm air leakage, even through concrete walls, is an essential element of radically reducing heating needs.
Windows: triple glazing, 12 times more insulating than the current windows.
Heavy construction: stores heat and cool to keep the house warm in winter and cool in the summer.
Passive solar: glazing to provide winter solar gains. Summer shading with the existing ash tree.
Low-energy lighting and A++ fittings to minimise electricity use, including an electric cooker with induction hob.
Solar roof: photovoltaic (PV) panels will convert the sun’s energy into electricity and any surplus can be exported to the national grid. This offsets the electricity that will imported (for example at night).Solar hot water: roof panels use the sun to heat hot water, stored in a large cylinder.
Ventilation system: supplies fresh air warmed by recovering 95% of the heat from extracted stale air. Another essential element in preventing heat loss.
Wood-burning stove: top-up space and water heating fuelled by wood from the garden. The heating needs are so low that prunings from 2 large ash trees will be sufficient. The regrowth of the trees captures the carbon dioxide emitted by the stove.

Zero Carbon House, Birmingham UK » Energy

What does “zero carbon” mean?

Energy design summary