(a) Notwithstanding the provisions of a charter or special act, a zoning commission may adopt, as part of the zoning regulations adopted under § 8-2 or any special act, regulations establishing an incentive housing zone in accordance with the provisions of sections 8-13m to 8-13x, inclusive.

(b) An incentive housing zone shall satisfy the following requirements:

(1) The zone shall be consistent with the state plan of conservation and development and be located in an eligible location.

(2) The regulations of the zone shall permit, as of right, incentive housing development.

(3) The minimum allowable density for incentive housing development, per acre of developable land, shall be: (A) Six units per acre for single-family detached housing; (B) ten units per acre for duplex or townhouse housing; and (C) twenty units per acre for multifamily housing, provided that a municipality whose population as determined by the most recent federal decennial census is less than five thousand, when applying to the commissioner for a letter of eligibility under § 8-13q, may request approval of minimum as of right densities of not less than four units per acre for single-family detached housing, not less than six units per acre for duplex or townhouse housing, and not less than ten units per acre for multifamily housing. In making such request, the municipality shall provide the Commissioner of Housing with evidence of sewage disposal, water supply, traffic safety or other existing, substantial infrastructure limitations that prevent adoption of the minimum densities set forth in this subdivision. If the proposed incentive housing zone otherwise satisfies the requirements of this section, the commissioner may issue the requested letter of eligibility. A municipality may request a waiver of the density requirements of this subdivision and the commissioner may grant a waiver if the municipality demonstrates in the application that the land to be zoned for incentive housing development is owned or controlled by the municipality itself, an agency thereof, or a land trust, housing trust fund or a nonprofit housing agency or corporation. The proposed incentive housing zone regulation shall require, in an enforceable manner, that one hundred per cent of the proposed residential units will be subject to an incentive housing restriction, and the proposed incentive housing zone will otherwise satisfy the requirements of this section.

(4) In order to qualify for financial incentive payments set forth in § 8-13s, the regulations of an incentive housing zone concerning the minimum as of right densities set forth in subdivision (3) of this subsection shall constitute an increase of at least twenty-five per cent above the density allowed by the underlying zone, notwithstanding the provisions of said § 8-13s with regard to zone adoption and building permit payments.

(5) The minimum densities prescribed in subdivision (3) of this subsection shall be subject only to site plan or subdivision procedures, submission requirements and approval standards of the municipality, and shall not be subject to special permit or special exception procedures, requirements or standards.

(6) An incentive housing zone may consist of one or more subzones, provided each subzone and the zone as a whole comply with the requirements of sections 8-13m to 8-13x, inclusive.

(7) The land area of an incentive housing zone shall not exceed ten per cent of the total land area in the municipality. The aggregate land area of all incentive housing zones and subzones in a municipality shall not exceed twenty-five per cent of the total land area in the municipality.

(c) A zoning commission may modify, waive or delete dimensional standards contained in the zone or zones that underlie an incentive housing zone in order to support the minimum or desired densities, mix of uses or physical compatibility in the incentive housing zone. Standards subject to modification, waiver or deletion include, but shall not be limited to, building height, setbacks, lot coverage, parking ratios and road design standards.

(d) If a zoning commission adopts a regulation for an incentive housing zone that permits single-family detached homes on subdivided lots, requiring subdivision approval under the subdivision regulations of the municipality, the zoning commission shall make a written finding that the applicability of such subdivision regulations will not unreasonably impair the economic or physical feasibility of constructing housing at the minimum densities and subject to an incentive housing restriction as required in sections 8-13m to 8-13x, inclusive. If housing on subdivided lots is proposed in an incentive housing zone, the zoning commission shall use its best efforts to adopt or encourage the planning commission to adopt subdivision standards that will ensure consistency of the single-family detached housing with the purposes of sections 8-13m to 8-13x, inclusive.

(e) The regulations of an incentive housing zone may allow for a mix of business, commercial or other nonresidential uses within a single zone or for the separation of such uses into one or more subzones, provided that the zone as a whole shall comply with the requirements of sections 8-13m to 8-13x, inclusive, and that such uses shall be consistent with as-of-right residential uses and densities required under this section.

(f) An incentive housing zone may overlay all or any part of an existing historic district or districts, and a municipality may establish an historic district within an approved incentive housing zone, provided, if the requirements or regulations of such historic district render the approved housing incentive zone not in compliance with the provisions of sections 8-13m to 8-13x, inclusive, the commissioner shall deny a preliminary or final letter of eligibility, deny or revoke a certificate of compliance, or deny any financial incentive payments set forth in § 8-13s.

(g) An applicant for site plan or subdivision approval to construct an incentive housing development within an approved zone may, through an incentive housing restriction, exceed the minimum requirements for such a development as follows: (1) More than twenty per cent of the total proposed dwelling units may be subject to the restriction; (2) the maximum annual income of qualifying households may be less than eighty per cent of the area median income; or (3) the duration of the restriction may be longer than thirty years. An application for approval of an incentive housing development may not be denied on the basis that the proposed incentive housing restriction contains one or more of the provisions set forth in this subsection.

(h) The provisions of this section shall not be construed to affect the power of a zoning commission to adopt or amend regulations under chapter 124 or any special act.