(a) A person is guilty of arson in the second degree when the person intentionally damages a building by starting a fire or causing an explosion.
(b) In any prosecution under this section it is an affirmative defense that:
(1) No person other than the accused had a possessory or proprietary interest in the building, or if other persons had such interests, all of them consented to the accused's conduct; and
(2) The accused's sole intent was to destroy or damage the building for a lawful purpose; and
(3) The accused had no reasonable ground to believe that the conduct might endanger the life or safety of another person or damage another building.
Arson in the second degree is a class D felony.