Engine 16 Retrofit project, New York, NY

The goal for the Engine 16 retrofit project was to rehabilitate the mixed-use, multi-family residential building while increasing efficiency, without compromising the historic character

Updating for efficiency while preserving the past 

Located in Manhattan’s Kips Bay, 223 East 25th Street is a former firehouse built for Metropolitan Steam Fire Engine Company 16 in 1882. The building features a classically-informed, cast iron and rose-colored brick façade adorned by historic aesthetic elements including sturdy Corinthian columns, dog-tooth detailing above the window spandrels, terra cotta tiles and a statement cast metal cornice. The building was decommissioned and sold in the 1960s and, over time, fell into a state of disrepair. It received its new lease on life in 2018, with the new owners engaging Baxt Ingui Architects to redesign and retrofit the former firehouse into a mixed-use, multi-family residential building. The plans sought to preserve the façade and many of the historical features, while adding two additional floors to create a five-story structure housing four residential units and a ground-floor community facility.   

The Goal: Adaptive re-use and retrofit to Passive House standard 

The goal for the Engine 16 Retrofit project was to rehabilitate the building while increasing efficiency, without compromising the historic character. The design and build team targeted the Passive House Institute’s (PHI) EnerPHit Classic certification, the established Standard for the refurbishment of existing buildings using Passive House components or the energy demand method via climate zone. Because of the numerous buildings of similar scale and condition in New York City, the project sought to be a model to promote a systemic, replicable approach to EnerPHit, highlighting best practices and the benefits that a deep energy retrofit can bring to a historic property—preventing demolition that can be costly from a monetary perspective, avoiding lost history, and reducing embodied carbon. 

The Challenge 

The building envelope presented the greatest challenge for the Engine 16 project. It was imperative to the owners and design team that the façade of the building be preserved. While the architectural firm was limited in possible approaches to retrofitting the front of the building due to its historical significance, fewer restrictions allowed for greater design freedom in updating and retrofitting the rear exterior. The exterior wall needed to meet the requirements of New York’s Local Law 126 (LL126)—a recent update to the building code that is inclusive of new and more strict requirements for keeping building enclosures fire safe. The code update goes above and beyond those of the International Building Code, establishing new protocols for fire-blocking concealed spaces within exterior walls and limiting the use of combustibles around windows, balconies, and other penetrations of the structure. In addition to LL126, designers sought an exterior wall that would help control moisture, improve thermal and acoustic performance, and incorporate more sustainable materials. 

The Solution 

Several factors made this Exterior Insulated Finishing System (EIFS) incorporating ROCKWOOL Frontrock™ stone wool insulation boards an attractive option in the New York City market. Primarily, the system, with its noncombustible insulation, allowed for steel framing without additional fire-blocking requirements or additional NFPA 285 testing. The EIFS wall assembly, covering approximately 1,000 sq. ft., also added passive fire resilience to the building, with Frontrock stone wool insulation boards resisting temperatures up to 2,150°F. This can be especially important in New York and other high-density urban centers in zero- and reduced-lot-line installations. EIFS wall assemblies with ROCKWOOL Frontrock may be permitted for construction in Types I through V as outlined in the International Building Code (IBC) and may also be permitted for use around balconies and in retrofits where no sprinklers are installed. In addition, these EIFS wall assemblies address energy efficiency including requirements such as the International Energy Conservation Code (IECC) model code and state- or city-specific standards such as Local Law 97 in New York City. 

Frontrock stone wool insulation within the EIFS wall assembly provides excellent R-value (R4 per inch) and contributes to greater energy efficiency, in keeping with the project goal to achieve EnerPHit Classic certification. Use of this exterior wall system will help reduce energy demand, maintain long-term thermal performance over the life of the building, and keep indoor temperatures more stable, protecting occupants during power outages or unplanned events impacting mechanical systems. Retrofitting with Frontrock as part of an EIFS wall assembly will help future-proof the building, ensuring it can stand the test of time and conditions for generations to come given its historical significance. Sample testing from existing buildings shows that ROCKWOOL stone wool retains its performance for 65 years. Plus, the combination of air sealing and insulation in this project can help reduce the need for heating and cooling of interior spaces by 80 – 90 percent.  

Incorporating Passive House measures, the building’s design and architect team also sought to reduce the carbon footprint of the existing building. Frontrock stone wool insulation is made primarily from natural and recycled materials, including basalt rock (abundant in the earth). The architects also liked ROCKWOOL’s commitment to transparency, given the company’s numerous certification and listings, Environmental Product Declaration (EPD), Lifecycle Assessment (LCA), Health Product Declarations (HPDs), and voluntary participation in the Declare labelling program that promotes healthy building materials through product transparency and ingredient disclosure. The Declare Label for Red List Approved was important to ROCKWOOL’s specification in the EIFS wall assembly and the Engine 16 Firehouse retrofit project. 

Moisture management was also a key benefit provided by the stone wool EIFS wall assembly. The insulation boards allowed for easy application of the adhesive ribbons to create an effective drainage plane compliant to ASTM E2273. The EIFS with stone wool insulation provides excellent vapour permeability, allowing any vapour or moisture ingress to dry to the inside or the outside of the assembly. Ultimately, the vapour permeability and drying potential of the system appealed to the owners, given the potential to mitigate moisture issues, reduce the chances of costly remediation in future, and increase the long-term durability of the historic building.  

Frontrock insulation boards, installed in 2” and 3” thickness for this project, also help reduce sound transmission from outside to inside, which can be a significant hinderance impacting resident productivity, sleep, and wellbeing in dense, noisy metropolitan centres. The stone wool EIFS can help improve indoor environmental quality and occupant comfort. 

During installation, Frontrock insulation boards helped conform to any unevenness or irregularities of the substrate. Mechanical fasteners are used for permanent securement of the insulation boards and to support wind load resistance of the assembly. The EIFS wall assembly overall provides compatibility with a number of substrate materials where approvals permit its use, including brick and masonry, concrete, wood, gypsum, providing wide appeal to architects and designers. Brick, block, and gypsum were the primary substrates for the Engine 16 Firehouse project. The stone wool insulation boards were easy to cut around penetrations including exhaust vent piping and window and door openings. The dense stone wool boards also facilitated the use of recessed fasteners which were then covered by stone wool plugs to help reduce both thermal bridging and reading of the fasteners into the lamina.  

ROCKWOOL Frontrock provides sufficient compressive strength and flexibility to support the EIFS lamina and provides rigid surface resistance against accidental impacts to the wall assembly. The inherent qualities of the insulation also help the boards act as a buffer for differential movement between the substrate and the lamina. Frontrock has been shown to be dimensionally stable when tested to ASTM 356, with minimal linear shrinkage. As such, it can be relied on to provide long-term thermal performance without gapping. Tested in accordance with ASTM E2486, the stone wool EIFS provides excellent impact resistance, meeting or exceeding industry standard.