Zero carbon housing
Most commonly zero-carbon housing is taken to mean zero emissions of carbon dioxide, which is the main climate pollutant from homes, although fugitive methane may also be emitted from natural gas pipes and appliances.
The Chancery Lane legal climate project gives 6 definitions of zero carbon housing or buildings,[1] of which 2 explicitly allow for the inclusion of off-site emissions reductions, via off-site renewables or other carbon offsets, and one is a net zero definition, allowing for net renewable energy export to be included.
For a refurbishment to be genuinely zero-carbon, the embedded carbon needs to be "paid back" by the emissions saved by the house within a timescale relevant for action on climate change (normally within a few years), and well within the lifetime of the equipment concerned.
While these are currently (2024) few (eg Iceland, Nepal[4]), a significant number of countries are targeting zero carbon electricity grids by 2035, including Austria, Belgium, Canada, France, Germany, Luxembourg, the Netherlands, Switzerland and the UK.
For this reason some governments provide householders with grants or subsidies towards the cost of the shift, for example the Boiler Upgrade Scheme[12] in the UK, which helps to fund heat pump installations.
In this situation the house will typically import electricity for heating and other purposes in the winter, and export excess solar power in summer.
Home batteries are widely used with solar power, to provide electricity at night or dull conditions, and for cost advantage where export rates are low.
At a national / economy level greater domestic energy efficiency reduces the need for large scale grid generation and transmission infrastructure, and electricity imports.
Opponents of fabric first suggest that major building upgrades such as wall and floor insulation and new windows are expensive and disruptive, and may deter residents from taking any action at all to move their homes towards zero carbon.
By comparison, they say, energy supply equipment such as heat pumps and solar PV panels are cheaper and deliver larger reductions in carbon emissions and bills.
In hotter climates a house can be orientated North-South to minimise insolation in the middle of the day and reduce overheating and cooling demand, although having a south facing roof for PV is still an advantage.
High insulation and air tightness: this applies to all elements of a building envelope, ie floors, roofs, walls, windows and doors.
Zero carbon houses offer much cleaner indoor air because they curb fossil fuel combustion which releases volatile gases and pollutants.
Appliances such as gas stove, heaters, dryers, and ovens that rely on burning fuel inside the home worsen the air quality indoors and can lead to respiratory issues for the occupants.
[21] Replacing appliances that run on fossil fuels can improve indoor air quality and reduce asthma symptoms in children by up to 42%, as well as decrease fire hazards in homes.
[21] It is now routinely possible to achieve net zero carbon housing, even without significant energy efficiency retrofit, by combining heat pump and solar PV technologies.
This gives a total electrical demand of 5,900kWh per year, which can be supplied by a solar array of about 6.3 kW (figures derived from Energy Saving Trust calculator in 2024[23]), which is about 16 panels.
