But inside, things are very different – because this is Ulster’s greenest home.

Property firm Sky Developments has designed and built a pad so eco-friendly it would free residents from the misery of ever-increasing household bills.

In 2006 Gordon Brown decreed that all new homes in Britain would be zero-carbon rated by 2016, the first time any country has made such a sweeping promise.

Sky Developments’ directors Stephen McCready and Alan Johnston are giant steps ahead of him.

Number 5a The Esplanade in Holywood, open to the public for the first time today, is Northern Ireland’s first zero-carbon property – meaning it has no running costs.

If it was for sale, it would probably go for something in the region of £700,000.

Builders of carbon-neutral homes say the asking price is justified by future savings.

Carbon-neutral homes must use green methods to produce more energy than they use, liberating the homeowner from oil, gas and electricity costs.

Stephen and Alan say the 2,300sq ft home is so energy efficient that Northern Ireland Electricity will owe the householder £200 at the end of the year because it will produce so much energy it will feed the surplus back into the grid.

Stephen, 47, said: “The technology built into the structure will provide 130 per cent of the energy needed for lighting, heating and cooking.

“That means 30 per cent is fed back to Northern Ireland Electricity, making the home an extra £200 a year.”

The house’s carbon-neutral status means it’s been granted an A Energy Performance Certificate.

Average Ulster homes are rated E and the UK’s 21 million houses are responsible for 27 per cent of CO2 emissions.

Stephen revealed his “green house” uses four main methods to keep costs at less than zero:

n the roof has been constructed of photovoltaic panels designed to resemble black slate tiles that harness the sun’s rays for electricity;

n structural insulated panels (SIPS) make up the shell of the house, with their superior heat-retaining ability cutting down on the need for electricity;

n an air source heat pump uses wind energy to pump out water at 37 degrees;

n quadruple glazing in each window blocks out the cold.

Underfloor heating has also been built into the first floor, but Stephen said it is not needed because the insulation is so effective.

“The lighting is also state-of-the-art.