THE HOCKERTON HOUSING PROJECT (HHP) IS THE UK'S FIRST EARTH SHELTERED, SELF-SUFFICIENT ECOLOGICAL HOUSING DEVELOPMENT. THE RESIDENTS GENERATE THEIR OWN CLEAN ENERGY, HARVEST

THEIR OWN WATER AND RECYCLE WASTE MATERIALS CAUSING MINIMAL POLLUTION OR CARBON DIOXIDE EMISSIONS. THE HOUSES ARE AMONGST THE MOST ENERGY EFFICIENT IN EUROPE.

By 2016 all new homes built in the UK will be expected to reach a zero carbon standard. According to the house building industry, reaching this standard will be extremely expensive, unrealistic, unfeasible or just plain impossible.

These views are supported by studies that give a detailed breakdown of the additional costs involved at different levels within the CSH culminating in the zero carbon house.

This view is at odds with our experience.
The question being asked is ‘How much extra will it cost to bring standard houses up to the required levels?’

Ask a different question ‘How do you build to this standard with no additional cost?’ you, perhaps surprisingly, find that it can be done.

The definition of a zero carbon home- ‘Where net carbon dioxide emissions resulting from ALL energy used in the dwelling are zero or better. This includes the energy consumed in the operation of the space heating/cooling and hot water systems, ventilation, all internal lighting cooking and all electrical appliances. The calculation can take account of contributions from on site renewable/low carbon installations’- can be found in the background documents to the CSH.

Using a ‘Green’ tariff is not permitted probably because many of these tariffs are green in name only. This leaves new on site renewable sources.

How much will it cost? We have to make the assumption that the average new house is not going to be on the optimum site for renewable energy generation. Very few sites include streams or rivers for micro hydro, or decent average wind speeds with no obstructions causing turbulence for wind turbines, or even unobstructed access to sunlight on the southerly façade. The most likely usable resource is sunlight as this is the only resource that can be optimised through the design of the house rather than selection of the site.

WE SHOULD ASK WHAT THE PURPOSE OF ZERO CARBON HOMES IS. THE ANSWER IS SIMPLETO REDUCE THE OVERALL CARBON EMISSIONS FROM THE HOUSING SECTOR.

Hold on! Is it being suggested that appliance energy is somehow different to heating, space heating, ventilation and lighting energy? That appliance energy can be generated anywhere, whereas all other energy requirements have to be generated on site or by private wire arrangement? Is this positive discrimination for the avid TV watcher [I include myself in this category], the toast and coffee consumer [and in this one] or the obsessive clothes washer and hooverer [not this one] Where is the logic?

There are other questions to be answered.
Does the on site renewable source have to last the lifetime of the house?

If the energy use calculation is theoretical, are the renewable sources output theoretical as well?

If not, who is going to monitor it and over what period?

If the house is extended, does the renewable source have to be upgraded?

If the house uses less energy with a different occupier can the occupier sell off some of the renewable source?

If the renewable energy source consumes more energy in its manufacture than it generates over its lifetime, does it still count as a renewable?

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.

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