Sri Lanka has all the right conditions for an eco-factory - warm enough to keep the windows open and wet enough to grow plants.

There is, of course, far more to it than that, but ultimately you need the right climate to prevent climate change itself. Solar powered lighting, harvested rain water systems and 'evaporative cooling', for instance, simply wouldn't work in much of Europe.

On the other hand, Asian countries with tropical climates have no excuse not to follow Sri Lanka's lead. Indeed, most of the Western buyers were drawn here for this year's Sri Lanka's Design Festival (SLDF) because of the country's green garment plants.

Today (11 November) just-style was given a guided tour of MAS Intimates Thurulie, the so-called 'eco-factory' famous for its green credentials.

The plant, opened in 2008 in conjunction with UK retailer Marks and Spencer's Plan A pledge, is designed to use 40% less energy and 50% less water than normal factories.

As soon as you step through the door there is an electric display of energy usage that working day. Next you reach offices that are kept at the right temperature by the evaporative system and a cooling grass roof.

The architecture of the building, meanwhile, is built into the landscape and uses bricks made of 10% cement and 90% soil. The building is surrounded by a large lake, with every drop of rain water used in the building or to grow trees that also keep things cooler.

A mainly female workforce at MAS, who produce lingerie products for M&S, are given plenty of space and natural light to go about their trade too.

MAS, which has 33 other factories in Sri Lanka, also makes sportswear and swimwear for brands including Nike and The North Face.

The firm's eco-plant snapped up a CIMA International Award for CSR in 2007 and is certified as an LEED Platinum factory.

"We are driven by a desire to make and change and not just for awards and recognition," says MAS's head of marketing Surein Wijeyeratne. "The most important resource we have clocks off and goes home at 5.30."

Aside from the bells and whistles, the MAS eco-plant is a template for how garment factories might look in the future.

But the dependence of this plant on the right weather demonstrates how location could be as important to sustainability as it is to sourcing.

Sri Lanka would do well to replicate this template, while buyers are feeling green and before its neighbours cotton on.