Notwithstanding the provisions of this chapter, chapter three or chapter four of this title, when a dwelling unit subject to this chapter is later reclassified by order of the commissioner, the supervising agency or by any other governmental agency supervising such dwelling unit, or by operation of law to a dwelling unit subject to any of the provisions of article II, IV, V or XI of the private housing finance law, regulation under chapter four of this title or the emergency tenant protection act of nineteen seventy-four, or when a dwelling unit subject to regulation under such act, chapter four or chapter three of this title is reclassified by order of the commissioner or the supervising agency or by operation of law to a dwelling unit subject to the provisions of article II, IV, V or XI of the private housing finance law or subject to a mortgage insured or initially insured by the federal government pursuant to section two hundred thirteen of the national housing act, as amended, a head of the household who held or holds a valid rent increase exemption order/tax abatement certificate at the time of the reclassification shall be issued a rent increase exemption order under this chapter or chapter four of this title, as applicable, continuing the previous exemption notwithstanding the reclassification of the dwelling unit.