RSA 540:13-d Defenses to Violations of Fitness.

I. No action for possession based on nonpayment of rent shall be maintained in regard to any premises leased or rented for residential purposes, other than for vacation or recreation, if such premises are in substantial violation of the standards of fitness for health and safety set forth in RSA 48-A or in local codes, ordinances or bylaws established pursuant thereto, and such violation materially affects the habitability of said premises, provided that:
(a) The tenant proves by clear and convincing evidence that, while not in arrears in rent, he provided notice of the violation to the person to whom he customarily pays rent; and
(b) The landlord failed to correct the violations within 14 days of the receipt of such written notice or, in an emergency, as promptly as con