Ventilation
Historic buildings often face unique challenges when it comes to energy efficiency. Due to aging infrastructure, outdated materials, and the need to preserve their architectural integrity, upgrading ventilation throughout the home can be laborious. Fortunately, older homes and buildings were often designed to maximize passive heating, cooling, and ventilation to make a living space comfortable. To improve indoor air quality, temperature regulation, and humidity in older buildings, property owners must find ventilation strategies that take advantage of the efficiency already inherent in historic buildings and balance them with modern technology.
Proper ventilation is often achieved through efficiency upgrades, including interior and exterior weatherization, HVAC systems, and insulation. However, there are three broad strategies for improving ventilation in a home:
Natural ventilation: In the past, natural ventilation came through the natural gaps in the home and through windows and doors. Natural ventilation is often used in warmer climates and homes without central air. However, because many homes in the northeast are at least partially sealed, natural ventilation may be insufficient as the sole method for pollutant removal, heating, and cooling. Additionally, while still beneficial, natural ventilation is less reliable than other methods because air fluctuates with the weather and seasons.
Spot Ventilation: Spot ventilation can help ease the burden on exhibiting systems by adding additional air circulation in high areas with high pollution or humidity. Bathroom fans and vent hoods above stoves are examples of spot ventilation.
Whole-House Ventilation: Whole-house ventilation is the most intrusive of the three options, requiring mechanical systems to force air into and out of the building. While there are different types of ventilation strategies, the key components of whole-house ventilation are fans, ducts, duct terminations, and free-flowing air circulation indoors.
Ventilation Strategies for Energy Efficiency
Air sealing and insulation: Ensure the building envelope is properly sealed and insulated to minimize air leaks and improve the effectiveness of ventilation systems.
Natural ventilation: Use operable windows, vents, and other passive techniques to promote airflow and reduce reliance on mechanical systems.
Heat recovery ventilation (HRV) systems: Install HRV systems to recover heat from exhaust air and preheat incoming fresh air, reducing heating and cooling demands.
Demand-controlled ventilation: Implement sensors and controls to monitor indoor air quality and adjust ventilation rates accordingly, optimizing energy use.
Preservation Considerations
Sometimes, it may be necessary to make changes to maintain a healthy and comfortable environment; however, if preservation is the highest priority, there are a few key considerations:
Minimizing intrusions: Choose ventilation systems that minimize alterations to the building's structure and aesthetics, such as ductless air conditioners, or add to existing systems when possible. If a new whole-system approach is needed, consider raised floors or drop ceilings to disguise ductwork.
Reversible modifications: When possible, look for reversible or removable systems that do not permanently damage the interior or exterior of the building. Such modifications may include retrofits for improved insulation, removable AC units, and fans.
Compatible materials: Use materials compatible with the building's original construction and have minimal visual impact.
Before updating existing heating, ventilating, and Air Conditioning systems, please consult the U.S. Department of Interior’s Guidelines on Sustainability for Rehabilitating Historic Buildings to preserve as much of the original property as possible. Properties that are Certified Historic Landmarks or part of the National Register of Historic Places must follow these guidelines or risk losing their financial incentives.
