Protecting a National Historic Landmark requires more than meeting prescriptive code requirements. It demands a fire protection strategy that balances life safety, property protection, and preservation of irreplaceable historic materials. RAN Fire Protection Engineering was retained by H2M architects and engineers to design a comprehensive fire detection and hybrid suppression solution for Grant Cottage in Wilton, New York, the site where President Ulysses S. Grant spent his final days.

The structure consists of a basement, two stories, and an attic. The first-floor rooms are maintained as they existed at the time of President Grant’s death, placing strict limitations on visible system components and invasive construction. Additional constraints included limited available water supply, winter interior temperatures maintained at approximately 55 degrees Fahrenheit, and the need to minimize structural alterations within fragile framing and concealed cavities.

System Selection and Code Analysis

RAN conducted a detailed site walkthrough and review of existing documentation, followed by a comprehensive code analysis to establish the applicable fire protection requirements. Multiple suppression strategies were evaluated against the owner’s objectives, which prioritized full building protection while preserving historic finishes and architectural features.

Traditional wet or dry pipe sprinkler systems were determined to be unsuitable due to water supply limitations and the potential for collateral water damage to historically significant materials. High pressure water mist alternatives were also evaluated but would have required extensive bracing and structural reinforcement that conflicted with preservation goals.

The selected solution was the Victaulic Vortex hybrid fire extinguishing system. The system was designed in accordance with the manufacturer’s published design criteria and the draft edition of NFPA 770, Standard on Hybrid Fire Extinguishing Systems, to ensure compliance with emerging industry standards for hybrid technology.

Hybrid Suppression Engineering

The Victaulic Vortex system utilizes a dual agent discharge consisting of nitrogen and ultra fine water mist delivered through a common nozzle assembly.

• Nitrogen discharge reduces the oxygen concentration within the protected space from 21 percent to approximately 14 percent within three minutes. This concentration is below the threshold required to sustain combustion while remaining tenable for occupant egress.
• Water mist discharge produces droplets in the 10 micron diameter range, creating a fog that cools the fuel surface and surrounding gases to prevent re flash while significantly limiting water usage compared to conventional sprinkler systems.

To preserve historic finishes, piping was concealed on the first and second floors and permitted to remain exposed in the basement where visual impact was less critical.

A dedicated, conditioned tank room was constructed beneath the porch to house nitrogen cylinders, water storage tanks, and control equipment. HVAC was provided to maintain environmental stability for system components.

The hybrid system’s lower operating pressure reduced structural bracing requirements compared to high pressure alternatives, allowing installation with minimal impact to historic framing and concealed structural members.

Detection and Integration

Because hybrid suppression systems depend on precise activation, early and reliable detection was a critical component of the overall strategy. RAN specified an air aspirating smoke detection system capable of very early warning through continuous air sampling. Multiple alarm thresholds were established in coordination with the owner to allow investigation and response prior to system discharge.

The integrated fire alarm and releasing design included:

• A new fire alarm control panel
• Dedicated releasing panels for Vortex system activation
• Manual pull stations and audible and visible notification appliances in accordance with NFPA 72
• Carbon monoxide detection in compliance with New York State requirements

The detection and releasing sequence was coordinated to ensure code compliant operation, controlled discharge, and reliable system performance.

Conclusion

Through detailed code analysis, system evaluation, and multidisciplinary coordination, RAN delivered a fire protection solution that satisfies modern performance standards while preserving the historic fabric of this nationally significant structure. The project demonstrates how hybrid suppression technology can be thoughtfully integrated into preservation sensitive environments without compromising life safety or architectural integrity.