True Cost of the 2012 IECC for New Homes in Idaho Climate Zone 5 True Cost of the 2012 IECC for New Homes in Idaho Climate Zone 5 This fact sheet provides background on the costs of building new homes in Climate Zone 5 in Idaho to the 2012 IECC and demonstrates how quickly would-be homebuyers would break even on the added investment. Maureen GuttmanAIA President Washington, DC