Operable Windows
INSIDE THE FLOODPLAIN | OUTSIDE THE FLOODPLAIN

What Is It?

Cost: Site, size, and project specific. Operable windows will typically cost 50 – 75% more than fixed windows.
Applications: Can be installed in retrofits or in new construction.
Service Life: 30-35 years

The installation of operable windows can give building occupants greater control over building temperature. During cooler summer days where outdoor air temperature is comfortable, building windows can be opened to allow for natural ventilation. In buildings with mechanical ventilation systems, the need for cooling and its associated energy costs will be reduced. Operable windows are essential in buildings that utilize passive ventilation strategies for cooling (i.e. cross ventilation and stack ventilation). Operable windows can also provide backup ventilation in the event of power outages or during other times when ventilation systems are inactive. A wide variety of windows are available depending on building needs and location.

Operable windows will have a larger capital cost compared to fixed windows, though the additional cost can be offset by reduced energy use for cooling and increased worker comfort and productivity. Not all windows in a commercial building need be operable; 15 to 20% operable windows positioned to allow for cross ventilation can be a cost-effective investment for a building owner. Ultimately, the cost-effectiveness of operable windows will often depend on occupant behavior. While building occupants will typically be more satisfied with having greater control over some workspace/living conditions, building energy use may increase if occupants do not properly close or open windows during the winter.

Benefits

  • Operable windows allow for greater control over building temperature. This can result in increased building occupant satisfaction and productivity.
  • Building energy use can be reduced if less mechanical cooling is required when windows are opened.
  • Operable windows can be washed from the inside, potentially reducing cleaning/maintenance costs.
  • Provide continued ventilation during power outages or other HVAC downtime.

Drawbacks

  • Operable windows are significantly more expensive than fixed windows.
  • If windows are left open or improperly closed, a building ventilation system can experience excessive heating or cooling loads, increasing energy costs.
  • Benefits of operable windows require buildings to utilize multiple HVAC zones so that the system can be switched off when windows are opened. These ventilation systems are more expensive and place space configuration limitations on realizing the benefits of operable windows. Failing to shut off HVAC systems when windows are opened can increase energy use for that area by as much as 30%.
  • May be impractical on the upper floors of high rise buildings. Wind levels may be too high due to the stack effect or higher outdoor wind speeds.

Regulatory Impacts and Requirements

A summary of potential regulatory touchpoints follows below.
Operable-Windows

Additional Resources

Project Examples

SAMPLE OF SUPPLIERS

SOURCES

Photo Credit: National Parks Service, Image is part of the Public Domain