Planning construction that is green-friendly has become an expectation for architects and builders.

However, most buildings standing today will still be in use for decades. The challenge is to modify existing buildings so they are more energy efficient. The “built environment” is massive compared to new construction and bringing it into a green future, while managing costs, is a major hurdle.

The most cost-effective solution to this is “green retrofitting” older buildings.

Retrofitting is the most cost-efficient way to combat climate change and save on power bills according to analysis from the Mckinsey Institute and the International Energy Agency.

Older buildings often have outdated heating, cooling and lighting systems and can have air leaks. This means they are the worst for energy consumption and carbon emissions.

Many older buildings are now trying to achieve the goal of a green future through retrofitting.

One of the biggest retrofits to take place is on New York’s Empire State Building. The 102-storey historic building can now add ‘Energy Efficient’ to its list of attributes.

The project dedicated to retrofitting the building was motivated by the desire to find the truth about cost-effectiveness of energy efficient retrofits. Developed in 2010, the project achieved a 38% reduction in energy use, with measurements and verification continuing to monitor the return on the investment.

The Clinton Initiative, Jones Lang LaSalle, Rocky Mountain Institute, Johnson Controls Inc and the Empire State Building Operation all played a part in the retrofit. Upgrades that were carried out were balanced between financial and environmental returns, which included window retrofits, upgraded heating, ventilation and air-conditioning, improved air quality, lighting and tenant education.

A five per cent reduction in energy usage was recorded with just retrofitting the more than 6000 double hung windows. Other strategies contributing to the 38% reduction include the installation of digital demand controls, an air handling unit, retrofitting the chiller plant and tenant energy management.

Not only has energy efficiency being the most valuable benefit from this retrofit, thermal comfort for the tenants has been improved.

With such an iconic building able to achieve these results, a buzz of inspiration has sparked around the world. Melbourne has developed a scheme called the 1200 Buildings Programme in order to address the 48% of greenhouse gas emissions produced by commercial buildings across the city.

Retrofitting 1200 existing commercial buildings in Melbourne is expected to decrease greenhouse gas emissions by 383,000 tonnes over the next decade and improve energy performance by 38%.