That's a huge increase from the Productivity Commission's estimate of between 2 to 5 percent. The carbon footprint of New Zealand's buildings currently takes into account operational emissions like heating and lighting.

But the author of the Thinkstep report, Jeff Vickers, said their approach only took into account what was produced, not what was consumed.

"If you factor in the whole life cycle so taking account of production of the building products, also the operational energy and end of life, you get to a number that's 20 percent of New Zealand's total.

"It changes the game on how significant the built environment really is," he said.