Separate specifications for building contracts.

Every officer, board, department, or commission charged with the duty of preparing specifications or awarding or entering into contract for the erection, construction, or altering of buildings for the state, when the entire cost of such work shall exceed $10,000, may have prepared separate specifications for each of the following branches of work to be performed:

(1) Heating and ventilating and accessories.

(2) Plumbing and gas fitting and accessories.

(3) Electrical installations.

(4) Air-conditioning, for the purpose of comfort cooling by the lowering of temperature, and accessories.

All such specifications may be so drawn as to permit separate and independent bidding upon each of the classes of work enumerated in the above subdivisions. All contracts hereafter awarded by the state or a department, board, commissioner, or officer thereof, for the erection, construction or alteration of buildings, or any part thereof, may award the respective work specified in the above subdivisions separately to responsible and reliable persons, firms or corporations regularly engaged in their respective line of work; provided, however, that all or any part of the work specified in the above subdivisions may be awarded to the same contractor.