ID request: The builder intends to purchase and retire certified CO2 offset credits sufficient to "neutralize" the contribution of greenhouse gases due to extraction, manufacturing, assembly, and delivery. Based on available data, the average house embodies ~40 tons of CO2 emissions. The builder would purchase credits from projects that avoid or sequester 40 tons of CO2, as validated by the Chicago Climate Exchange (see www.chicagoclimatex.com). Invoices and appropriate documentation could be provided.