(a) In this subchapter, "new residential construction" includes:
(1) residential construction of a single-family house or duplex on a vacant lot; and
(2) construction of an addition to an existing single-family house or duplex, if the addition will increase the square footage or value of the existing residential building by more than 50 percent.
(b) The term does not include a structure that is constructed in accordance with Chapter 1201, Occupations Code, or a modular home constructed in accordance with Chapter 1202, Occupations Code.