Greener building practices could cut North America's greenhouse gas emissions more effectively than any other available measure. Canada, Mexico and the US are being urged to embrace greener construction methods That is the conclusion of a new report from the Commission for Environmental Co-operation (CEC). Green Building in North America: Opportunities and Challenges says buildings release about 35% of the continent's total CO2 emissions and this could be the quickest and cheapest way to reduce North America's impact on climate change.