The Manager's report back on potential amendments to the Affordable Housing Overlay (AHO)

In consultation with local affordable housing builders, an additional suggested edit was made to the red lined text which allows particularly small lots (5,000 square feet or less) to waive required open space when the lot abuts a Public Open Space that consists of at least 1,500 square feet of contiguous area. The result would allow smaller lots to redevelop under the AHO where providing open space on the lot itself would be infeasible, while ensuring future residents would have access to open space resources directly adjacent to the site.

Consultation with Local Affordable Housing Builders on Proposed Amendments

In preparing this response, we consulted with Cambridge affordable housing builders regarding the proposed modifications to the AHO and confirmed their support for the amendments being proposed. They expressed broad interest in exploring ways to maximize the affordable housing benefits of a site by building taller buildings and welcomed the proposed change to the AHO to allow heights of 12 stories in the corridors and 15 stories in the squares. Notwithstanding this interest, builders noted that, for the near future, it is unlikely that many AHO 2

developments will exceed 11 or 12 stories due to other constraints beyond zoning:

• Funding: A fully affordable building of larger size requires substantial financing subsidies from multiple sources. While local funds are more readily accessible, it is challenging to secure the amount of state and federal funding needed to complete a development of that scope.

• Construction Technology: At this time the most feasible option for affordable housing construction is light-gauge steel, which has its own limitations as a construction method. It is expected that building technology will keep improving and will provide a wider range of options to make high-rise construction more feasible in the future, including buildings taller than 15 stories. This includes emerging construction technologies such as mass timber, that are emerging and should expand what is feasible, construction-wise, for 100% affordable housing developments.

Viability of Mass Timber Construction Pathways for Affordable Housing

Mass timber construction, also known as cross-laminated timber (CLT), is construction that uses multiple thick, compressed layers of wood, either nailed or glued together, as structural components to a building. This is not to be confused with heavy timber, which is a traditional construction method using heavy beams to create a framing system. Mass timber construction is allowed in jurisdictions that have adopted the 2021 International Building Code (2021 IBC).

Under this building code, the use of mass timber is allowed for buildings up to 18 stories in height. The Massachusetts Board of Building Regulation Standards (BRRS) is currently considering the adoption of the 2021 IBC, which would include the new mass timber construction pathways (types IV-A, IV-B, and IV-C). BBRS has been meeting since 2022 regarding this potential change, and a vote is expected in Summer or Fall 2023.

If approved, mass timber construction will be permitted use in buildings up to 18 stories in Massachusetts. 3

Two buildings in Massachusetts have already been built using mass timber: UMass Amherst John Oliver Design Building and 201 Hampden Street in Boston. Though mass timber is not yet allowed in Massachusetts, both projects were able to obtain a variance that allowed them to do so. While mass timber is not yet widely available, it is an emerging technology which could be useful for building affordable housing in the future.

We expect that once approved for use in Massachusetts, there will be some time for builders to learn about how best to utilize the technology, and to assess its cost in comparison to other construction types. Staff will continue to monitor the approval of the 2021 IBC and this new construction approach. When the new building code is adopted here, staff will work with affordable housing builders to understand where it might be advantageous to consider this construction approach to build new affordable housing.

Amend Article 2.000 as follows:

AHO Corridor – One or more Lots with frontage on one or more of the following streets: Albany Street, Alewife Brook Parkway, Bishop Allen Drive, Broadway, Cambridge Street, Concord Avenue, First Street, Fresh Pond Parkway, Massachusetts Avenue, Memorial Drive, Mount Auburn Street, Prospect Street, and Sidney Street.

AHO Square – One or more Lots located entirely within the confines of the Central Square Overlay District, Harvard Square Overlay District, Lesley Porter Overlay District, or the area bounded by the centerline of Elm Street to the west, the Somerville/Cambridge municipal boundary to the north, the centerline of Windsor Street to the east, and Cambridge Street to the south; but not including ML 81-50, ML 81-101, or ML 81-100.

Amend Section 11.207 as follows:

11.207.5.1 General Provisions (a) For the purposes of this Section, the phrase "District Development Standards" shall refer to the development standards of the base zoning district as they may be modified by the development standards of all overlay districts (with the exception of this Affordable Housing Overlay) that are applicable to a lot.

(b) District Dimensional Standards shall include the most permissive standards allowable on a lot, whether such standards are permitted as-of-right or allowable by special permit. A District Dimensional Standard that is allowable by special permit shall include any nondiscretionary requirements or limitations that would otherwise apply.

(c) An AHO Project that conforms to the following development standards shall not be subject to other limitations that may be set forth in Article 5.000 or other Sections of this Zoning Ordinance, except as otherwise stated in this Section. (d) An AHO Project containing more than one base zoning district shall follow the requirements of the zoning district that covers the largest percentage of the area of the lot or development parcel, as if the entirety of the lot was served by a single zoning district.

Section 3.32 shall generally not apply to development that proceeds under the provisions of this Section 11.207. (e) Where an AHO Project may have various applicable Building Height and Stories Above Grade limitations as specified in 11.207.5.2.1, the most permissive height limitations shall generally control. Notwithstanding the provisions set forth in Section 11.207.5.2.1, an AHO Project may match the height of an existing building on an adjacent lot. 11.207.5.2.1 Building Height and Stories Above Grade.