I know from personal experience that greenwood (freshly cut) does not provide as much heat energy as seasoned wood (has been down for 6-12 months). When burning it spends a lot of it's energy boiling the water out of the wood. It takes more green wood to provide the same amount of heat as you would get from seasoned wood.
Assuming I let my firewood season for 12 months, if I burn seasoned fire wood and my neighbor burns green wood, how much more fire wood will he burn in season?
According to the Wikipedia article Heating value of firewood there are a lot of variables. I am just looking for general rule of thumb. I always burn seasoned wood, but my neighbor just moved into his homestead and will need to burn greenwood this winter. How much more wood should he expect to need, compared to my normal usage?