Case Study: Consulting Engineering

Ingalls Building

SREE HotelsCincinnati, Ohio

Achieving Sustainability in a Historic Preservation Project

Built in 1903, the 83,000 SF Ingalls Building in downtown Cincinnati, Ohio, is recognized as the first concrete-reinforced high-rise building in the world, standing at 16 stories. In the 1970s, the building was given landmark status by the American Society of Civil Engineers and added to the National Register of Historic Places. Unfortunately, the space was partially abandoned and fell into disrepair in the 2000s, igniting the need for a complete renovation to revitalize the building. This project demonstrates that historic preservation does not require sacrificing sustainability and energy goals in an urban community.

The Challenges

  • Renovate the building while preserving historic architecture and beauty
  • Pursue sustainable design and significant energy goals in an urban community
  • Design and install systems that allow for easy maintenance
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We completely brought the energy and life back into the building...The simple architectural details that are here, they are original. We wanted to make sure that we could salvage what we could...We had to put the extra work in to make sure that it looks the way it used to. Created with Sketch.

Vernon Burchett

Courtyard Marriott General Manager

The Solutions

The facility program utilizes the basement spaces for operational back-of-house and a guest gym, the lower two levels for public gathering, dining, and cooking, the upper 13 floors for guestrooms, and the top-level and roof for MEP infrastructure.

The 2020 renovation and hotel conversion balanced sustainable design decisions with historic preservation goals—a challenge when receiving preservation tax credits that prioritize historical aesthetics. CMTA worked closely with the owner to implement multiple cost-shifting measures to keep LEED and energy goals intact. Our team overcame several constraints to achieve drastic energy reduction. First, the tight, 5,000 SF urban site eliminated the option for a geothermal wellfield. The west facade imposed a significant and unavoidable solar heat gain with a window-to-wall ratio of 0.4. Historical criteria constraints prevented removing, externally shading, or significantly altering the glazing. To circumvent these constraints and increase the building’s energy efficiency, storm windows were incorporated, reducing the U-value of the windows from 1.0 to 0.5. Additionally, a layer of spray foam insulation was added to the uninsulated concrete walls, increasing the R-value from R-2 to R-22.

High-efficiency water-source heat pumps (WSHP) were chosen for space conditioning, with a cooling tower and condensing boiler used for heat rejection and addition. The guestroom WSHP temperature sensor uses passive infrared occupant-sensing to reset the temperature when the room is vacant, maximizing energy efficiency. The high-rise design meant building pressurization was especially important. Ventilation and exhaust are provided 24/7—as required by the hotel standards—via the roof-mounted dedicated outside air system (DOAS) with sensible and latent energy recovery. To promote guest comfort and prevent winter infiltration due to the stack effect, the DOAS unit was designed to provide outside air 100% above code. This positively pressurizes public spaces and allows the building to maintain less than 800 ppm of CO2 when the space is fully occupied.

In addition, a one-pipe mechanical design was chosen to save 30% of total piping, fitting, and labor costs. In place of traditional supply and return piping, the one-pipe design allowed quicker installation and reduced the overall project budget without sacrificing efficiency.

An added egress stair, existing concrete columns, and new MEP shafts meant the 3,000 SF floorplate had to be carefully programmed to achieve the desired guestroom count. This tight floorplate left no room for floor-mounted mechanical equipment. The owner had negative prior experiences with above-ceiling horizontal WSHPs, as access was inadequate. The design team worked with the owner to arrive at a solution that mitigated their concerns over maintenance while keeping the floor plan compact. Each guestroom entryway includes 8-foot ceilings to accommodate a vertical WSHP—not a typical high-rise heat pump—in the space above because of a 14-foot floor-to-floor. A single hinged 30” x 30” access panel is all that is required to maintain the unit and its runout piping accessories. The filtered return grille allows for a 2” pleated filter to be easily replaced from the floor without requiring ceiling access.

Carbon Footprint of Historic Building

Though the overall goal of the project was to preserve and restore the historic character of the building, the renovation also proved to be environmentally friendly. The overall carbon footprint outpaces a comparable new build partly because of the decision to renovate the 110+-year-old concrete building. A new construction project of identical size and scope, with an EUI of 106 (Zero Tool for 2030 Challenge), emits 32% more CO2e on an annual basis. Additionally, the embodied carbon associated with a new construction project is around 4,000 Metric Tons of CO2e. The embodied carbon associated with the Ingalls Building, however, is around 250 Metric Tons of CO2e, mainly accounting for finishes and interior frame walls.

The total carbon (operational and embodied) associated with a new building is approximately 40,000 Metric Tons of CO2e, compared to just 25,000 Metric Tons of CO2e associated with Ingalls. This amounts to a 38% reduction over 30 years. The annual carbon emissions decrease over time, as the electrical grid is expected to become cleaner in the coming decades. As a result, the cumulative emissions flatten out over the study period. Thus, by choosing to sustainably renovate the Ingalls Building rather than construct a new facility, the structure's carbon footprint is significantly reduced for both the short and long term.

The Results

CMTA was proud to partner with SREE Hotels to renovate the historic Ingalls Building. This project proves that historic preservation does not require sacrificing energy efficiency or sustainability. Rather, through innovative design and collaboration, renovations can modernize a building’s MEP systems while maintaining the historical integrity and architectural beauty of historic buildings.

Ingalls Building Energy Use

What does this data mean?
Baseline: The Measured Energy Use Before the Renovation
Actual: The Measured Energy Use of This Project After Renovation