INTRODUCTION There are several debates over the existence@ causes@ and effects of global warming; however@ most people agree that anthropogenic emissions have increased over the last 100 years. World human-sourced greenhouse gas (GHG) emissions increased 70% from 1970 to 2004@ and carbon dioxide (CO2) emissions grew 80% in this same time period and accounted for 77% of the total 2004 GHG emissions (IPCC 2007). GHG emissions are coming increasingly under voluntary and regulatory controls as the world moves toward reducing our impact on climate change. Terms such as carbon footprint and carbon offsets are becoming common parts of our daily language@ but they are not well understood. There are several on-line carbon calculator tools to help interested users@ but these tools often produce different results and there is little information about how they should be applied to buildings. We naturally want an easy solution such as a single number with our monthly utility bills. The utility companies are very good at measuring how much energy they sell@ but going from the energy sold back to the primary energy used and calculating the emissions associated with delivered energy are problematic. There are other sources of emissions and tracking them all down can be challenging. This paper examines many issues associated with estimating these emissions and provides recommendations about what should be included in calculating GHG emissions from building operations.