'A beacon of hope' and 'a modest masterpiece' - those are some of the superlatives bestowed on a Norwich council estate which has just won the title of the best new building in the UK.

Eastern Daily Press: Goldsmith Street in Norwich. Pic: Tim Crocker.Goldsmith Street in Norwich. Pic: Tim Crocker. (Image: Tim Crocker)

But, just what is it which makes the £17m Goldsmith Street homes so special and led to it scooping the Royal Institute of British Architects (RIBA) Stirling Prize.

Here are five of the features which so impressed the judges:

1. They are ultra-low energy

Eastern Daily Press: Goldsmith Street in Norwich. Pic: Tim Crocker.Goldsmith Street in Norwich. Pic: Tim Crocker. (Image: Tim Crocker)

The homes have been built to rigorous 'Passivhaus' environmental standards - good for the environment and for the wallets of people who live there.

Timber-framed homes have insulation pumped into an airtight membrane to prevent heat loss, with triple-glazed windows.

The homes are also kitted out with a mechanical ventilation heat recovery system. That is essentially a duct which comes into the building, with a fan blowing fresh air in and another duct with a fan blowing stale air out.

A heat exchanger takes the heat from warm air, produced by the likes of washing machines, televisions and body heat. It then transfers that heat to cold air, so that all rooms are a comfortable temperature. Each property also has a radiator, just in case a boost is needed.

Annual energy costs are estimated to be 70pc cheaper than for the average household).

To maximise solar gain, all homes face south and every wall is over 600mm thick, and the roofs are angled at 15 degrees to ensure each terrace does not block sunlight from homes in the street behind.

2. It's the little things which make a difference

Even the smallest details have been meticulously considered: letterboxes are built into external porches, rather than the front doors, to reduce any possibility of draughts; and perforated aluminium 'brise-soleils' provide sun shades above the windows and doors.

3. It's a proper community

More than a quarter of the site is communal space. The back gardens of the central terraces share an alleyway for children to play together in, while a wide area for communal gatherings runs through the middle of the estate. Parking has been intentionally pushed to the edges of the estate - so people, not cars, own the streets.

4. The modern design harks back to the city's past

The palette of building materials references Norwich's history, such as the glossy black roof pantiles - a nod to the city's Dutch trading links - and the creamy clay bricks, similar to Victorian terraces nearby.

To ensure the windows echoed Victorian proportions but also met 'Passivhaus' requirements, the architects developed a recessed feature, giving the impression of a much larger opening but limiting the amount of glass.

Bespoke steel mesh garden gates and brightly coloured front doors give each home a strong sense of individuality and ownership.

5. It's a rarity

RIBA president Alan Jones praised Goldsmith Street as "a beacon of hope" and lauded Norwich City Council for its construction.

It is the first social housing project to win the Stirling Prize, at a time when not many councils are building such homes.

All of the properties are let through the city council's Home Options scheme on secure tenancies.

The judging panel said: "This is proper social housing, over ten years in the making, delivered by an ambitious and thoughtful council. These desirable, spacious, low-energy properties should be the norm for all council housing.

"Goldsmith Street is a ground-breaking project and an outstanding contribution to British architecture."

The homes - a mix of 45 one-bedroom flats, 40 two-bedroom houses, three two-bedroom flats and five four-bedroom flats - were built by RG Carter and designed by architects Mikhail Riches and Cathy Hawley.

MORE: What is it like to live in the Norwich homes named the UK's best new building?