Exploring Natural Ventilation in the Healthcare Setting

Healthcare architecture today places a high priority on views and daylight, but not the more physical connection to the outdoors through an operable window. Recently, increased awareness of patient comfort now provides spaces that feel less “institutional,” however the risk of infection limits the creation of spaces that breathe.

of hospital’s annual energy costs is from heating/cooling/ventilation (according to the Energy Information Administration)

With industry initiatives like the 2030 Challenge and other sustainable design initiatives, hospitals must find ways to reduce their energy consumption while continuing to provide increased levels of patient comfort and care.

We conducted a national survey to better understand the current opinion on natural ventilation in the United States from the perspectives of designers, engineers and facilities personnel. While most designers favored the incorporation of operable windows, there still remains suspicion from facilities personnel about the impact an open window has on infection control, patient safety, controllability and thermal discomfort. If natural ventilation is incorporated in a healthcare setting, the top benefits include; the connection to the natural environment for patient healing, resiliency planning to help keep the hospital ventilated during a natural disaster and reduced operating cost due to potential energy savings.

Part of the challenge to incorporating natural ventilation in hospitals is tied to local environmental conditions that must be analyzed to determine if natural ventilation is appropriate and how often it could be utilized throughout the year. Some climates in the United States are more favorable, like San Francisco with its mild weather year round, while others, like Miami are too hot and humid most of the year to make natural ventilation a viable energy savings strategy. Then there are climates like Boston that have hot, humid summers, and very cold winters, where natural ventilation could only be used in the shoulder seasons.

In Europe, natural ventilation is much more common due to their more mild weather and energy consumption limitations. In Southeast Asia despite hot and humid conditions, natural ventilation is provided with the assistance of a fan to help draw air through the room while also providing thermal comfort through increased air flow to create the sensation of cooling. Both these regions provide many case studies that can be analyzed to better inform designing for natural ventilation here in the United States.

Beyond climate, designers must be able to analyze the effective area of a window to determine whether or not there is adequate ventilation provided to a patient. There are two ways of determining what constitutes adequate ventilation: providing for the required ACH (Air Changes per Hour) based on building codes or looking at a strategy that takes ACH and combines it with analysis of air speed to determine thermal comfort by limiting drafts. These metrics are further impacted by patient safety such as screens and window limiters to prevent falls and the amount of façade available in which to locate windows.

While an individual patient room can be designed to provide thermal comfort and meet the minimum air change requirements, ventilating the shared public spaces of a patient wards/ floor proves more difficult. With current hospital planning often resulting in the creation of a double loaded corridor of patient rooms very few areas have available exterior façade to locate and position windows effectively. The incorporation of a ventilation shaft is necessary for this type of ward configuration to allow greater displacement between where air comes in versus where it is allowed to exit to allow the natural buoyancy of warm air to rise while pulling cold air in. The sizing of the shaft is then determined similarly to calculating the effective area of an individual window.

 
Ventilating shared public spaces in a patient ward/ floor is greatly impacted by the available area of façade in which to locate windows along with the height of an internal ventilation shaft.

Overall, our research aimed at identifying relevant design and patient care issues, and outlined safe and effective approaches for incorporating natural ventilation into the healthcare setting. After exploring the current best practices in natural ventilation and lessons learned from some of our current projects, we are eager to use our new knowledge when designing future projects at PAYETTE.

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