In China, the area of existing buildings in urban and rural has exceeded 43 billion m(2) at present and more than 90% of them are high energy consumption buildings, which have poor thermal insulation performance, low energy efficiency technologies and equipments, and severe energy waste in HVAC system. Carbon trading, in construction field not only promotes energy efficiency retrofit of existing buildings and energy-saving technologies, but also reduces the financial pressure of government. The most important technical issue is how to estimate the carbon trading volume reasonably. Based on the requirements of energy efficiency retrofit of existing buildings, relevant national or professional standard standards and CDM small scale project methodologies, this paper puts forward a simplified and practical method of checking and certifying the carbon trading volume of existing buildings retrofits in China and calculates four typical cases for trail. Moreover, a comprehensive methodological framework is presented to make the method guide actual cases more directly and apparently. The framework comprises project analysis, scenario determination, data collection and envelope calculation. (C) 2013 Elsevier Ltd. All rights reserved.