Time for a sustainability quiz (I know, right – the best kind), so here’s your starter for ten. What links the following? A Venetian-Gothic water tower in London built in 1877. A heavy-goods barge, dating back to 1909, now on one of Stockholm’s islands. A water-pumping station in Yorkshire built in 1848. An iconic Manhattan water tower. And a century-old petrol station in New Orleans. The answer, of course, is that they’ve all been turned into homes.

Sprucing up old buildings isn’t new – though it’s usually dumpy office buildings which seem to get a makeover and turned into stunning houses or loft apartments. (Architects also seem to have a yen for converting churches and shipping containers into homes.)

In any event, faced with a growing population and a deepening housing crisis, making the most of the existing built environment and repurposing it is a smart and sustainable solution. After all, more than half of the current building stock in the world will still be standing in 2050, with this figure closer to three-quarters for OECD countries. Preservation and adaptive reuse should very much be the watchwords.

More interesting though, are plans to develop buildings in ways that create new, affordable and energy-efficient ways of housing – and at same time help to decrease buildings’ carbon emissions. That’s the approach to the existing built environment taken by Northeast Collaborative Architects, and one project in particular is its calling card.

Early last year, the firm transformed one of America’s oldest shopping malls into a series of energy-efficient, contemporary “micro apartments”. Though the architects respected the historic design of America’s first indoor shopping mall – the Arcade Providence, built in Rhode Island in 1828 – gone are its boutiques and balconies. Instead it boasts 48 micro lofts and 17 micro retail spaces.

The apartments are furnished one-bedroom units with storage, bathrooms and kitchens. Cosy is the word that springs to mind. The apartments range in size from 21 to 42 square metres (225 to 450 square feet) and doubtless appeal only to tenants who don’t need much space or mind sharing amenities such as ovens and stoves. Mind you, they don’t have to go far for food: the ground floor has an array of shops and restaurants, plus a lounge. And with monthly rents starting at $550, is it any wonder that the waiting list long ago topped 1,000 people?

Even so, it’s the sustainable design elements that matter, not the floor plans. The Arcade boasts high-efficiency gas units, new double-hung windows, a central skylight that provides extensive daylight, and a new insulated roof that reduces the building’s cooling requirements and minimises the urban “heat island” effect. What’s more, the carpeting is 100 per cent recyclable and all appliances in the micro apartments are ENERGY STAR certified.

Besides the environmental benefits, there are crucial economic and social benefits stemming from the preservation of Providence’s almost 200-year-old mall. For one thing, the micro lofts provide affordable housing in an urban area. And because they’re near social gathering spaces, they provide a degree of connectivity that helps support downtown businesses.

Meanwhile, the rejuvenation of the landmark mall has revitalised the city’s business district, with even more buildings being renovated. All of which goes to show that if the ambition is lofty enough, even the most shopped out of spaces can be reborn for future generations.

This innovation is part of Sustainia100; a study of 100 leading sustainability solutions from around the world. The study is conducted annually by Scandinavian think-tank Sustainia that works to secure deployment of sustainable solutions in communities around the world. This year’s Sustainia100 study is freely available at www.sustainia.me – Discover more solutions at @sustainia and #100solutions

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