NCATs approach has been to improve energy efficiency without forcing dramatic changes in building or construction techniques. NCAT has developed several prototype designs and has distributed more than 1.000 sets of energy efficient house plans. Several hundred houses have been constructed using these plans. For example. in South Dakota. an Indian housing authority is currently developing housing for migrant and seasonal farmworkers using NCAT plans. NCAT is currently working with the State of Montana to build five homes based on these plans. These homes yielded annual savings of over $500 for heating and $150 for hot water. when compared with comparable HUD units.