The Old Stone House is the oldest building in Washington, DC, constructed circa 1765. The three-story stone structure, located in the heart of Georgetown, serves as a historic house museum for the National Park Service with a furnished first floor open to the public. The building is listed on the National Register of Historic Places.

The renovation includes repairs and reconstruction of the stone foundation and walls, upgrades and replacements to the HVAC system, and renovations to the electrical and plumbing systems, to include lighting system upgrades.

The Old Stone House’s construction, age, and historic nature pose air temperature and humidity control challenges. Challenges include relatively high HVAC loads, significant air leakage into the building, limited space for replacement systems, and lack of insulation and vapor barrier in the walls. To address these challenges, Summer Consultants designed a heat pump with  refrigerant hot gas reheat and electric heating. The hot gas reheat will help to dehumidify the building in the summer. The design makes use of air leakage into the building as natural ventilation. Due to the lack of insulation and vapor barrier, humidification is not provided to avoid condensation buildup on windows and walls during winter months.