Alan Mackay, your comment is a very naive view of business and the building sector. House Builders, (like all businesses) aim to maintain and increase their existing profit margins.

When house builders look to purchase land, they will calculate their profit margin based on curret house prices, land prices and build costs - not what they expect the house to be worth in say 12 months time once built. For example, if land costs = £60k, build costs = £25k, and the current market value of the house = £100k, the builder will be hoping to make the £15k as profit, in otherwords a 15% profit margin. Any extra costs related to 'Green Housing' will increase build costs and in order to maintain their margin, the house builder will have to pass the costs on to consumer and, for example, increase the house price to £110k.

Any additional profit made due to a rise in house prices is fortunate and will be of benefit to the builder but they also take the risk should house prices fall.

Nick, London, UK

The model shown here (and indeed all of Barratt's eco-village) is nothing more than that of a regular house with good insulation and lots of 'eco-bling' bolted on. Compensating for the inadequacies of accepted 'standard' construction houses by throwing pieces of technology at them to see if they stick is not a responsible approach.

Good low/zero carbon designs integrate material considerations, solar orientation and environmental factors right from the start to produce designs that naturally perform better with less energy.

Barratt & other volume house builders have already chalked up scores of miserable anonymous boxes around the outskirts of Bristol - please tell me we're not seriously thinking of holding them up as exemplar house-builders because they bought a few turbines and heat-pumps, etc.

Renewable energy is good, but it's only a small part of the picture.

Ben Harries, Bristol,

"All new homes built from 2016 must be carbon-neutral, according to new rules issued in March." It is the running costs of the building which need to be carbon neutral not the construction. I agree with the writer regarding their style and look. Planners are going to have to get ahead of the curve for once as most builders claim to be able to deliver CN homes but in reality few can. In Scotland Das Securities are seeking to build their DAS home (dwellings achieving self-sufficiency.) These buildings have been under development since 1986 and are light years ahead of anything else currently proposed. However, the pricing should be viewed as the cost of prepaying for an element of the buildings' energy needs up front rather than by way of quarterly bills to the local electricity and gas supplier who will become redundant for this type of building. Das Securities define the DAS home as one not requiring connection to external services for energy.

DiJit, Glasgow, Scotland

Surely the challenge is to build a zero Carbon house which is also desirable and aspirational- unlike those built currently for the purpose of marketing and promotion of the manufactures and housebuilders producing them!

Ben, Hatfield, Herts

80-90,000 a building plot is already a heavy discount on the market rate of 150,000. The building companies are allsitting on land and keeping prices up, but do nothing but winge. Its perfectly possible to build an eco house for less than a normal house.

dave kendall, Bristol,

Why do we talk as if the housebuilders make a loss if there are extra costs involved in Green housing as the price of a house has very little to do with building costs and more to do with market conditions. A new house that cost 70,000 five years ago and now costs 200,000 is not because of increased building costs but because of market conditions.The 20,000 extra quoted for carbon neutral just comes of the builders huge profit margin.It is simply just less profit per house so there is no real reason for buyers to pay extra.

Alan Mackay, ABERDEEN, Scotland

Very low or zero carbon homes ar radically different from carbon neutral ones (which allows carbon offsetting) and a zero carbon home will look very different indeed from the carbon neutral home in your illustration.

The only prototype zero carbon home built to date is at the Building Research Establishment's site at Garston. Called the "Lighthouse, it is a highly unusual shape, rather like a slice of cake. The "Lighthouse" has a biomass boiler and photovoltaics, a heat recovery system, roof-mounted wind catcher and light funnel, and a solar thermal array. Zero carbon homes will be radically different in operation and appearance from more traditional new build homes; the acid test is whether the public (and local planning authorities ) will like them and whether purchasers are happy to pay considerably more money for them.

Vivien Aldred, Norwich, UK

Just one question. Define ' carbon-neutral ' As usual with people with ' vision ', their utopian dreams are already results in their minds. When the real results come in, as not being what they said they would be, watch out.! The person who argues against the ' vision ' will be vilified, and the results held up to ridicule. Facts are an ' inconvenient ' truth to the elites.

Desmond Taylor, Houston, USA Texas

Just a more costly house. Why are we being taken in by all this. The house will cost £30.000 more. You will never get that mony back in energy saving. Are these the same people that think wind farms are the answer.

Johnny Norfolk, Mileham Norfolk,