Will Anderson's home radiates warmth on a cold, clear November day. It's 10C outdoors, and a toasty 20.5C inside – but not a single degree of that warmth is generated by energy from the national grid.

When Anderson completed his house in 2006, zero carbon homes were few and far between. But since a government target announced in the same year by Gordon Brown to build all new homes with zero-energy demands as standard by 2016, dwellings like Anderson's will not be such a rarity.

Even the current financial crisis has given the zero-carbon initiative added impetus. As the conventional construction industry suffers, the sustainable building industry has seen an opportunity to grow. Early findings from a survey this week from the UK Green Building Council (UK GBC) indicate that sustainable building is a growth sector.

Asked whether the financial crisis has impacted on their organisation in tackling sustainability, 56% of its members said sustainability had become a bigger focus. Only 18% said the credit crunch has had an adverse effect on efforts to address sustainability.

Paul King, the chief executive of UK GBC, says: "I think we've seen an end to 'boom and bust' for sustainability. This time it's going to remain high on the political and corporate agenda because the climate change imperative is now so strong. This is reflected in what the building industries are facing in terms of government policy and regulation – not just in the UK but around the world. Failure to adapt and innovate will lead to obsolete buildings and obsolete companies. Those that grasp the opportunity will prosper, those that don't will fail. UK-GBC members recognise this and want to be among the winners not the losers."

Zero-carbon building focuses on renewable sources of power and reducing demand for heating, which accounts for around half of the UK's carbon dioxide emissions.

Electricity at Anderson's Tree House is produced on the roof by 30 square metres of solar photovoltaic panels supplied by Solar Century. Their output peaks at about 4.3kW and even on a late autumn day, his PV panels had produced more than 5KWh by mid morning.

The panels generate around 4,470kWh of electricity a year and is used to power the lights, appliances and a heat pump which provides underfloor heating throughout the house. The excess – 118KWh last year – is sold back to the grid.

As the energy bill nears the statute books, Anderson believes that feed-in tariffs, where the price of electricity exported to the grid is at a fixed rate, will stimulate greater interest in zero carbon homes.

"I can't wait for feed-in tariffs. It's an obvious way to stimulate the market and it's worked well in Germany. It just depends on what tariffs are agreed," he says.

Anderson's house is so successful at producing its own energy that over the year it is a net exporter of electricity, making it a carbon negative house.

But energy production is only part of the story, says Anderson. Tackling energy demand in the home is instrumental in achieving the government's target of reducing carbon dioxide emissions by 80% by 2050. Anderson calculates that he consumes around 4,400Kwh of power a year whereas the UK average is around 26,000Kwh.

"There is a lot of fretting in the building industry about how to achieve a zero spec, but it's all to do with demand. People get obsessed by the supply side. And the supply side, with all the technology is more visual, so fair enough. But the key thing is to get the demand down. Insulation and airtightness are key.

"Airtightness is a very big thing and that's what we're not very good at in this country. That was one of the biggest challenges because builders had never done it before. We actually used Canadian details for air tightness. So we have a draught-free house."

The house was pressure tested by experts who sealed the doors and windows and installed a huge fan to see how many air changes there were in an hour. They found there were around 2.3 air changes an hour - most buildings have more than 10 changes an hour.

Optimism in the green building trade is also supported by the government's apparent determination not to let its plans to tackle climate change become derailed by economic conditions.

A spokesman for the Communities and Local Government ministry says: "Our long-term priorities must not be forgotten. Climate change is one of the most pressing issues facing not only this country but the entire world. With buildings contributing more than a quarter of our carbon emissions, we must take our responsibilities in this area seriously."

While making new build zero-carbon is realistic, the challenge for the government is reducing emissions from its existing housing stock.

"We have already tightened house-building standards to deliver a 40% reduction in the level of carbon emissions from an average new build home since 2002, alongside a £1bn programme to improve the energy efficiency of existing homes. We will continue to increase the sustainable standards for new homes, and from 2016 they must be zero-carbon — the most demanding timetable in the world."

Later this week Boris Johnson will unveil his housing strategy, the latest in a series of big policy initiatives this month. He has five billion quid at his disposal to help him meet his campaign pledge to provide Londoners with an extra 50,000 "affordable homes" over the next three years by various means. How will that money be spent? Where will those homes become available? What does "affordable" actually mean?

We already know that the policy's main thrust will be a shift in emphasis away from the provision of "social housing" for rent towards helping people on to the private sector housing ladder. The First Steps Scheme outlined in Johnson's election manifesto - no longer available online, as it ought to be - is designed to make shared ownership schemes available to a larger number of middle-income households - couples with combined incomes of up to £72,000 per annum would qualify. The mayor will surely argue that this will assist key workers vital to London's wellbeing, including many in the public sector. But where will it leave those in the acutest housing need?

Concern has already been expressed by Shelter's chief executive, Adam Sampson, after Johnson put into effect his promise to dispense with Ken Livingstone's policy of requiring London's boroughs to ensure that half of all the new accommodation they create had to be affordable. The new mayor wants to "work with the boroughs" instead of bossing them about and has now suggested a negotiable target for each one set in accordance with local circumstances.

As the invaluable Inside Housing has reported, this cooperation will extend to allowing boroughs to decide for themselves how much of their new "affordable" provision will be for social rent. Johnson won't insist that any of it is. He reckons his policy will help some 63,000 social renting tenants on to the property ladder but critics will ask how much use that is given the third of a million - and rising - on London waiting lists for social rented homes. "We simply don't have anything like enough of them," says a spokesman from the Local Government Association.

It's important to recognise that providing affordable homes however they are defined doesn't only mean building them - just as well, given the plight builders are in - but with housing associations finding it harder to invest in new socially rented homes those council waiting lists won't be getting shorter any time soon. In his victory speech in May the new mayor promised to address London's gross inequalities. It's hard to see how his housing strategy will help.

Dozens of Scottish homes were sold at knock-down prices in a one-off, multi-million-pound property clearance sale yesterday. Some were advertised with discounts of up to 40 per cent - nearly £100,000 off.

The biggest discount was on a penthouse flat in Kilmarnock; originally on the market at £245,000, it sold for £150,000. The buyer, Ian Hamilton, had queued with half a dozen others overnight and was at the front when the sale started at 8am yesterday. 'I loved the property and didn't want to run the risk of losing it, so queuing overnight seemed the best way to do it,' he said.

Mr Hamilton, who had never even considered living in Ayrshire before seeing the property, is now selling his Glasgow home and moving into the penthouse.

The sale followed the biggest price fall in at least 16 years in the Scottish housing market. The cost of homes dropped 4 per cent in the three months to the end of October, according to Lloyds TSB Scotland, bringing the average price to £165,398, down from £172,185.

Countrywide estate agents, which was running the sale, said it was giving developers, builders and investors a chance to clear their stock. Properties included repossessions, fallen-through sales and new homes and a quarter had been sold within two hours of the sale opening.

'This was a window of opportunity for first-time buyers, families, landlords and investors,' said Mairi Eckford, Countrywide's managing director in Scotland. Many of the 95 properties had tens of thousands slashed off the price and buyers were eligible for further discounts if they signed the contract on the day.

A detached four-bedroom house in Stewarton, Ayrshire, valued at £235,000, was offered at £165,000 and went for £160,000 to Alexander Wardrop and his wife, who had queued from 5pm. 'This is a perfect family house for us and our kids and is the best Christmas present we've ever had,' he said.

David Green, 24, managed to achieve what many of his peers are still dreaming of by buying his first home at the sale. The first-year student at Strathclyde University bought a two-bedroom apartment on the outskirts of Glasgow for £90,000 with help from his dad.

Michael Miller, Countrywide's sales director, said the company believed it was the first sale of its type in Scotland. 'Many builders and developers need turnover between now and the end of the year,' he said. 'It was designed as a one-off, but has been very successful and we may consider another one.'

It is a scene that would not look out of place in Soviet-era Belarus. Rank with weeds, parkland is dotted with burst pallets of bricks, drink cans, and a builder's broken barrow. A burnt-out car was recently towed away. Streetlights are missing or faulty on some roads. The new community centre is fenced off, its glass doors shattered by stones.

Welcome to Arbury Park, a "contemporary, attractive and vibrant" private development of 900 homes in affluent Cambridge. Residents lured here by jobs in the nearby science park and the developer's promise of a sustainable suburb boasting green spaces, shops, and excellent public transport are instead living in a desolate landscape created by the recession.

With 380 homes completed, two of the three big construction firms, Persimmon and Martin Grant Homes, have downed tools because of the meltdown in the housing market, leaving residents surrounded by large swaths of a derelict construction site.

Antisocial behaviour has flourished. Residents, many with young families, complain of hooded gangs roaming the streets and robbing garden sheds. "We've had trouble with kids throwing stones at the house when we moved in. The builders left loads of rubble outside which is ammunition for them," said Emma Wren. "There are no pavements so you can't walk along with a buggy. Even walking to the bus stop you have to go through long grass and weeds."

The master developer, Gallagher Estates, promised shops, cycle lanes, bus routes, a multi-function hall, all-weather sports pitches, children's play areas, and even a "sensory garden" for disabled families. A primary school and one well-equipped play area have opened, but residents are still waiting for the other facilities.

Stella and Yemi Macaulay were among the first residents, moving into their four-bedroom townhouse almost two years ago. The pavements on their street are still unfinished. "They said it was going to be a new luxury place but Arbury Park is like a construction site. It's like a rubbish dump," said Mr Macaulay. "There are no basic amenities." He feared the credit crunch would mean the estate would not be finished for another five years. "We don't know what is going to happen now. Nobody knows. When is the business centre going to come? When are they going to finish the pavements?"

Arbury Park is being rebranded as "Orchard Park", and an oasis of tidiness is maintained around the show homes, still open for business in the centre of the site. Elsewhere there are bollards, temporary fences, holes, and messy plots of unfinished construction work. Many roads lack finished pavements and are rough and muddy in wet weather.

"With the dark nights coming on and no street lights on some roads, most residents feel holed up in their houses," said resident Nick Warren. "I'm sure Gallagher are feeling the credit crunch just as much as anyone else, but they are contractually obliged to deliver all [the public facilities]. They cannot use the credit crunch as an excuse."

Severine Leclair struggled with her child's buggy to find a safe place to cross the busy main road outside the estate to catch the bus. She said: "They obviously didn't foresee that they would have to stop building, because it's half-finished everywhere."

Gallagher Estates said the housebuilder Laing was continuing to build while Persimmon and Martin Grant Homes had stopped "for the time being". In a statement, it said: "Where construction work has halted, the housebuilders are responsible for keeping their sites safe and tidy.

"As the building work slows down due to the current difficulties in the housing market, the main contractor appointed by Gallagher will be passing through the site tidying up and making all areas safe. A programme of works is in place for unfinished footpaths around completed areas to be surfaced by Christmas 2008 and additional street trees will be planted later this year."

It would not give a date for the completion of the suburb.

A spokesman for Gallagher Estates added: "There are many positive features of this development, which should not be forgotten or overlooked, including the high-quality play areas, public open spaces, tree planting, landscaping, the new primary school, the public transport links, the early delivery of award-winning affordable housing as well as the community centre and community art projects."

South Cambridge district council said it was working with the developer to "make sure everything is tidied and made safe" while work is halted.

Councillor David Bard said: "These are difficult times for the construction industry everywhere in the country. In South Cambridgeshire we are monitoring carefully the effect the credit crunch is having on planned development across the district."