Project 49
Even with a very low energy use home, the cost of installing renewables to achieve genuine zero carbon emissions is prohibitive for most self builders.
Perhaps we should ask what the purpose of zero carbon homes is.
The answer is simple-To reduce the overall carbon emissions from the housing sector.
To achieve this is not difficult. All new houses should be very energy efficient and offset their total energy requirements [from all sources] by energy produced from new renewable sources. The renewable energy source should be inextricably linked to the house rather than the occupier. [This prevents the renewables subsequently being sold on to another property which could then claim zero carbon status as well.] In addition there should be a mechanism for the renewable source to be maintained and/or replaced as necessary for the lifetime of the house.
The most cost and energy effective way of achieving this is for each house to ‘own’ a share in a large renewable source according to the actual energy usage of the house and the operational capacity of the source. This share would generate energy which has a value. After costs are deducted the net value could be paid out as a dividend to the share owner.
A share in a large onshore wind turbine will cost approx £1000 per kW of installed capacity. Our 5000kWh/pa house would need to purchase 3 kW of the installed capacity at a cost of £3000- 10% of the cost of an individual system- saving £29000. If the Treasury extended the zero stamp duty to houses which met the above criteria then the purchase of the renewable share would be cheaper than not purchasing it. The prospects for affordable zero carbon housing would look much more promising. The £200 odd dividend each year would be a helpful bonus.
The homes at Hockerton are extremely low energy users. The energy use for space/water heating, appliances, lighting and ventilation for all 5 houses was 18723 kWh last year. This is less than 30kWhm2/pa [21.5kWhm2/pa including sunspaces] 80% of the energy was produced on site from renewable sources. The remaining 20% came from a green tariff using 100% renewable sources.
We consider the houses have zero carbon emissions because we know this is the case. The CSH definition says we are not zero carbon.
The zero carbon specification is currently a recipe for very expensive housing. It doesn’t have to be that way. A functional approach to house design and a tweak in the definition contained in CSH will allow genuine zero carbon emission houses to be built within normal cost parameters. And that is where we should be heading.
For more information: For more information about the Hockerton Housing Project (HHP) see
www.hockertonhousingproject.org.uk email
hhp@hockerton.demon.co.uk call 01636 816902.
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