154 Broadway

154 Broadway is a Passive House pre-certified, 45-unit, market-rate multi-family residential building with a mass timber structure. Four stories of rental units sit over a podium of residential services and commercial/retail space. The podium is type IA construction, comprising a concrete composite deck, steel frame, and metal stud walls, while the residential floor slabs are CLT and bear on light-frame wood stud walls below. The CLT is typically 5-ply thick, with isolated areas 7-ply thick for longer spans. The project was one of two pilots for the use of eastern hemlock-tamarack CLT, which was deployed over common areas and in one accent wall to highlight the potential for native New England species in CLT construction. Steel HSS columns are threaded through the building from the podium slab to locations on the fourth and fifth floors where unique plan conditions required increased structural capacity. At the fourth floor, this was to carry a HSS beam spanning a fully glazed façade at the amenity room that provides views over an expansive green roof terrace of the Boston skyline, while at the fifth floor a 10-foot setback creates private unit terraces and reorients unit plans such that steel beams were needed for the increased spans.

The building is designed to Passive House specifications, meaning it is exceptionally airtight and features continuous exterior insulation around the building envelope for increased thermal comfort and energy efficiency. Sun shades over most south-facing windows minimize glare and unwanted solar gain in the summer while allowing solar gain in colder months to reduce heating loads. The project was designed to be “PV ready” on day one, and the owner has separately pursued permitting for a photovoltaic array that is being installed now to further reduce the building’s off-site energy loads. The project further reduces the carbon footprint associated with it through the elimination of on-site car parking, due to its location along major bus routes and within the walksheds of two light rail mass transit lines.

The project’s unit mix of mostly studio apartments (40 studios, three 1-bedroom units, and two 3-bedroom units) caters to young professionals to aid in the City of Somerville’s affordability goals by reducing demand from this demographic for family-sized units elsewhere. The compact units make efficient use of space and are complemented by a generous shared amenity room and large communal terrace on the fourth floor. The terrace’s green roof features trees and, along with landscaping in the rear of the ground level, decreases stormwater runoff from the project and enhances the urban canopy.

The façade design is inspired by the vibrant textures, colors, and scale of materials observed throughout the neighborhood and along Broadway. The ground floor features active retail frontage and residential lobby space, both with storefront windows to visually connect ground floor uses and the public realm. The height of the ground floor aligns with a key datum on the building just to the north for street front continuity. The upper floors of the building are clad in a mosaic of rainscreen siding, which reduces the massing by means of relief, shadow, and color variation. The front façade takes advantage of the depth of the windows for both shading and play of light throughout the day. The massing of the setback at the fifth floor recalls pitched roofs from the residential neighborhood, reinterpreted in a contemporary composition.