By Mark Kinver Science and nature reporter, BBC News

Fewer than 2% of US offices are classified as "green buildings"

Improving the environmental performance of buildings in North America can cut the region's carbon emissions more than any other measure, a study suggests.

The rapid take-up of current and new technologies could save the equivalent of the amount of carbon dioxide emitted by transport in the US, it concluded.

However, it added that developers and homeowners were not willing to pay the extra cost for energy saving measures.

Buildings are responsible for about 35% of the region's man-made CO2 emissions.

The report published by the Commission for Environmental Co-operation (CEC), an international organisation created by Canada, Mexico and the US, said it was possible for the most efficient buildings to consume 70% less energy than conventional properties.

Each year, it said, energy used by buildings in North America resulted in more than 2,200 megatonnes of CO2 to be released into the atmosphere.

But it said that it was possible to reduce this by 1,700 megatonnes, compared to a "business as usual" approach, by 2030.

'Low-hanging fruit'

"Improving our built environment is probably the single greatest opportunity to protect and enhance the natural environment," said CEC executive director Adrian Vazquez.

POWER HOUSES Percentage of national energy consumption used in buildings: Mexico - 17% Canada - 33% United States - 40% (Source: CEC)

"This report is a blueprint for dramatic progress throughout North America, mostly using the tools and technology we have on hand today.

"Green building represents some of the ripest 'low-hanging fruit' for achieving significant reductions in climate change emissions."

Despite the potential energy and financial savings, the study found that less 0.5% of homes in the US and Canada could be called "green buildings".

"At the moment, there is no real reason for the private sector to change its practice from a purely financial standpoint," explained Jonathan Westeinde, chairman of the CEC advisory group.

"Generally, because of the leasing and financing structures, there is a split incentive between the owner or developer who is making the financial investments, and the tenant or occupier who will benefit.

Insulating properties is the most effective way to reduce energy use

"I think this is where the biggest hurdle remains."

Mr Westeinde said the biggest energy reductions could be achieved by getting the basics right, such as installing the most effective windows, doors and insulation.

"The number one thing is the need to take an energy conservation approach, and not think about spending a whole bunch of money on leading edge technology.

"The next most cost-effective measure is passive measures, such as making the most of natural lighting."

Retro-fashion

The study also highlighted that "retrofitting" - improving the energy performance of existing buildings - was the most important factor when it came to reducing emissions in the region's property sector.

"It has been proven quite easily that new construction can perform much better for a minimal marginal cost, but we won't get anywhere unless we focus on existing buildings," Mr Westeinde said.

Almost three-quarters of the buildings that will be standing in 2050 have already been built, research shows.

He added that the report would hopefully pave the way for greater co-operation between the three nations to develop the necessary regulations to deliver energy savings in the property market.

This would, he said, enable local authorities to act as "gatekeepers to advance the green building agenda".

"Ultimately, every building out there gets a site plan or permit, and this happens at a municipal level.

"Federal and state level policies are great, but it is all about getting the right tools and channelling the right resources to the municipal gateway."