London (CNN) -- Mike Putnam seems right at home in front of the "Green Wall" in Skanska's London headquarters.
As UK CEO, Putnam explains the wall, and its grading from light to deep green, to employees and clients alike.
Along the wall are various projects in which construction giant Skanska is the builder or developer and show how "green" each project is according to current building industry standards.
"The journey is to "Deep Green", and that is how we describe it internally and externally," Putnam said.
"But when we look at our business plan to 2015, we say we want a certain percentage of our projects to be (carbon neutral). But we expect a big chunk of them to be somewhere in the middle, but moving in the right direction."
Skanska is behind some of the more well known buildings developed of late --the 'Gherkin' in London and the New Meadowlands Stadium outside New York City are two well known ones.
Maybe not so well known, but key to Skanska's aim to be the most green construction firm in the world, are a new "green" McDonald's in North Carolina and a new civic center being built right now next to Wembley Stadium in north London.
The McDonald's met the industry's gold standard in green construction (LEED Gold for Retail) and the civic center should be the first public building in the UK to receive the British equivalent -- the so-called BREEAM Outstanding.
"We have deliberately positioned ourselves to be a leader, or the leading contractor in this space, in this whole green space," says Putnam.
To back up its claims, Skanska points to winning The Sunday Times newspaper's "Greenest Construction Firm" award in 2010.
Constructing "green" buildings is clearly a major step to cutting carbon emissions for companies. But these days its not just about more efficient light bulbs, rainwater capture, solar panels and green roofs.
Its about the "greening" the whole construction supply chain; its about clearing the site and reusing the rubble and waste in the new build; its about well placed stairways so employees walk more, its about being close to public transport.
For the civic center at Wembley, it's about using vegetable oil as the fuel to generate heat in the building.
Skanska runs seminars for its suppliers to help them become more green. Its also initiated a four-year plan in the UK to switch some 2,000 company cars over to hybrids - 65% now are.
"Yes, it costs us money," says Putnam when talking about the company's entire green push.
"We've had a pretty significant investment in the UK, I would say, in recent years. Here in the UK, we spend £1 to 2 million ($1.6 to 3.2 million) per annum, but its starting to give us rewards. Our clients tell us, it differentiates us in the market."
In fact, Skanska says this past year the investment has increased to £4 million ($6.4 million).
Now Skanska is moving into a newer market -- retrofitting older buildings to be more green. Here the Swedish firm is joining with Arup and GE in a joint venture to supply companies with the tools to even make one floor of an older building more green - and to run tests to make sure the floor or building is ever closer to carbon neutral.
"Its very much in its infancy at the moment, so its only really the enlightened clients, the enlightened tenants, and enlightened developers that are taking that leap of faith... but we are convinced that in coming years its going to be big business," says Putnam.
And Putnam sets down a marker to any company in any field that calls itself green. "If you want to be a green company, then you have to live those values, and you have to be in a green building."