paul-fred,
Estimating the in-use carbon footprint is not too difficult, as, I assume, it is just proportional to the mass of fuel burned. If you want to include the carbon used in constructing the house, well, that is difficult.
Assuming you want to estimate the in-use carbon footprint, and you want to express it as the mass of CO2 released in the atmosphere, then you just need to do a chemical balance for completely reacting all the fuel used. For example, assume No. 2 fuel oil is the energy source. Fuel oil has a H/C molar ratio (atom ratio) of about 1.85. The atomic weight of H is about 1.0, and C is about 12.0. Therefore, fuel oil is made up of about 0.866 C, or is 86.6% carbon. When you completely burn carbon, you get CO2, which multiplies the weight of carbon by a factor of 3.667, since O has an atomic weight of 16. Multipling 0.866 x 3.667, I get about 3.175. So for each kg of fuel oil I burn, I create 3.175 kg of carbon dioxide. The specific gravity of fuel oil is about 0.85, so each liter of fuel oil creates about 2.70 kg of carbon dioxide. If you work in antique units, you can look up the conversions. I have no idea if this is the official approach for computing carbon footprint, but it is the way that I would do it.
For electrical power, you've got to account for generation losses and line losses. DOE gives a figure of around 3.3x times the electrical energy required at the source in terms of fuel energy, varying somewhat with the fuel type. You can look up the energy content for fuel oil, should be about 43 MJ/kg, and compute amount of fuel required to generate the electricity. Then go through same calculations above. |