Phillip Johnson's Glass House in New Canaan, Connecticut built in 1949 is on 47 acres and currently owned by the National Trust for Historic Preservation. Only the bathroom is enclosed. Johnson died at 98 in 2005.
Rice University Professor of Architecture Michael Bell's Hudson River Valley House evokes Johnson's design. Originally designed for the long impoverished Fifth Ward of Houston. Cost of building was $113K.
Werner Sobek's R128 House in Stuttgart, Germany is the efficient example we should move towards today.