Yet these are far from an easy option, which prompts the question: what do organisations stand to gain from them?
Royal Botanic Garden Edinburgh (RBGE) head of project management Chris Minty speaks for many when he says: "We're in the sustainability business - our ethos is to reduce our impact on the environment as much as possible."
Having completed a new sustainably built visitor centre at its regional garden at Dawyck in the Scottish Borders, RBGE's energies are now focused on an ambitious new welcome centre at its main Edinburgh site, to be called the John Hope Gateway in honour of an 18th-century keeper of the garden.
"Sustainable technology is becoming more and more affordable," says Minty. "The cost of things like solar panels are coming down, though they are still quite expensive. But as a concept it has to be economically viable."
Many design decisions involve trade-offs between initial outlay and anticipated savings in running costs, he says, and this has limited what has been achievable at Dawyck. "We've not been able to do everything we wanted to in terms of sustainability. We had to use concrete and we still have to draw energy from the National Grid."
Likewise, the Gateway, while boasting a wind turbine, will not be self-sufficient in electricity. But visitors will be able to monitor the energy the turbine generates. "The purpose is not necessarily to be state of the art, but to provide an opportunity to see what's possible," he says.
"The construction industry has been slow to pick up on the potential of sustainable technology," he adds. "But since we started plans for the Gateway five or six years ago, a lot more companies are developing environmental solutions.
"Bridging the two cultures of construction and horticulture is often challenging. But we were fortunate - Max Fordham Consulting Engineers has been extremely helpful in directing us to the right technology."
Such role-model designs have particular value in the context of tighter building regulations and initiatives in cities such as Edinburgh to promote green technology, he says. "It's becoming more mainstream because it has to - it's no longer the cranky option."
Minty's own recent work has served as a sustainability boot-camp, he adds. The RBGE's field station in Maya Forest, Belize, where he was previously based, is a five-hour Land Rover ride from civilisation and so had to be self-sustaining.
"There's nothing new about solar panels, wind turbines or water harvesting and recycling there," he says. "It's the hard end of sustainability."
The RHS has also put sustainability at the heart of recent projects in its gardens. According to a representative: "We are very focused on the environmental elements - it's part of our organisation's positioning."
On its new learning centre at Harlow Carr, where construction is due to begin in January, she says: "We've done a lot of consultation and taken a lot of advice. The building itself will be a teaching tool and during its construction we will give people the opportunity to see what goes into it."
Workshops involving planners, architects and other professionals are planned at the site from December onwards.
The new entrance building at RHS Hyde Hall in Essex, meanwhile, will also boast a rainwater harvesting system linked to the garden's reservoir, and heating via a ground source heat pump.
Public parks are also benefiting from the trend. Royal Parks director of major projects Greg McErlean says: "I've been here 12 years and it's been developing all that time. It's got more exciting - there are grant schemes, and help and encouragement out there, along with a growing awareness of the benefits. That's more powerful than legislation in moving it forward."
Opting for "green" buildings was originally down to the nature of the parks themselves and the effect of buildings on them, he says. "Earth shelter buildings gave us literally a green aspect. They also improve the thermal performance of the building, which can also be oriented to benefit from the winter sun."
But other approaches are being taken at the Royal Parks' new Heritage Lottery Fund-supported Pheasantry Welcome Centre, which is currently under construction in Bushy Park, south-west London.
"We reckoned the grass wouldn't establish on the roof and that you'd need a stronger structure," he says. "It doesn't have a conventional foundation, which means you don't have to cart around a lot of concrete."
The building is made of sustainably sourced timber and will be heated by a biomass boiler, though this will not be powered from wood arising in the park. "We have no facility to generate wood pellets at the moment," McErlean says.
Even small-scale projects can have an impact on the professions and public, says City of London's Burnham Beeches superintendent Andy Barnard. A new cafe and visitor centre at the Buckinghamshire wood, which opened last autumn, relied on locally sourced materials and labour.
"You have to push for sustainability," he says. "It's not hard, but you have to keep an eye on it. You have to include things like what you do with waste as part of the tender - what contractors can and can't do should be laid down from day one."
However, firms that Barnard approached were happy to meet such specifications. "They see it as a way of securing their future," he says. "Even a humble project is an opportunity to learn and expand, and profit from sustainable building in the future."
The buildings have shown that not every sustainable-building element is compatible with every other, he says. "We would have liked to be able to flush the toilets with collected rainwater, but with a green roof you get very little run-off."
However, the toilets have yielded a surprising economy in being lit entirely by natural light. "It saves in maintenance as well as electricity - there are no switches or bulbs to worry about, and no moving parts," says Barnard.
Light tubes conduct daylight from glass cones on the roof, which is then dispersed around the room by a diffuser in the ceiling. "The effect is amazing, especially in small rooms," he says.
One year on, Barnard reckons the building has been a hit with both trade and public. "The green roof gets a laugh, but then people want to know why it's there. So you can tell them about its role as a habitat and in minimising water runoff."
It also has a security purpose, he adds. "There's no one around at night and it would be easy to break in through a tile roof. But you're not going to want to dig through 10' of soil and membrane to get in."
Barnard is proud of the buildings' role in moving the sustainability debate forward. "We have a fantastic audience - half a million visitors a year - with a bent toward the environment and a lot of industry professionals among them," he says. "We've had local authorities and even the Scouts come to see the buildings.
"It's all about reaching a critical mass, so this sort of building becomes run of the mill."
SIX OF THE BEST
- John Hope Gateway, Royal Botanic Garden Edinburgh
Client: Royal Botanic Garden Edinburgh
Design: Edward Cullinan Architects
Completion: Summer 2009
This imposing timber, glass and stone construction boasts biomass boilers, rain-water harvesting and a wind turbine mounted on its sedum roof.
- Learning Centre, RHS Garden Harlow Carr, North Yorkshire
Design: Eco Arc Architects
Completion: Early 2010
Containing three teaching areas, a library and exhibition space, the new centre will allow a three-fold increase in school visits to the garden. It boasts a zero- carbon footprint and includes a natural reed bed sewage system in the surrounding landscape.
- Visitor Centre, Dawyck Botanic Garden, Scottish Borders
Client: Royal Botanic Garden Edinburgh
Design: Simpson & Brown Architects
Completion: May 2008
The RBGE's first bespoke visitor facility is built of heat-retaining blue limestone, and topped with a sedum roof. A biomass boiler provides underfloor heating.
- Visitor Centre, Anglesey Abbey, Cambridge
Client: National Trust
Design: Cowper Griffith Architects
Completion: June 2008
This "dry-build" project houses a restaurant, shop, reception area, function room, toilets and staff offices, and features automatic venting and air exchange as well as rainwater harvesting.
- Pheasantry Welcome Centre, Bushy Park, London
Client: Royal Parks
Design: Randall Shaw Billingham
Budget: around £1m
Completion: Spring 2009
Tucked away in woodland, this will consist of a cafe, toilets and reception area, giving information to visitors on all areas of the 450ha park, to encourage more adventurous use, and a community room.
- Cafe and Information Centre, Burnham Beeches, Buckinghamshire
Client: City of London
Completion: September 2007
Locally sourced green oak clads this green-roofed building in the heart of a 220ha woodland. Its green roof features grasses rather than the more usual sedum.