Low-speed fans provide needed ach at this remote mountain hospital.

All buildings, regardless of age, are susceptible to IAQ deficiencies. Chemical exposure from new construction, tight building envelopes, and humidity and moisture build-up are all contributing factors. Hospital settings are even more susceptible since airborne diseases can adversely affect IAQ. Both first- and third-world countries are up against the same predicament, yet obviously the resources available to improve conditions are unbalanced. The World Health Organization (WHO) set forth guidelines to introduce proper ventilation for facilities in several ways: natural air movement from open air environments, mechanical ventilation, or a hybrid (or mixed-mode) ventilation system.

Most western medical facilities employ intricate mechanical systems that not only regulate temperature as needed but help filter the air routinely throughout the day to remove airborne viruses. Other hospitals rely on natural ventilation to provide the needed fresh airflow. In Butaro, Rwanda, a mountainous community with a population of 340,000, architects utilized design as a tool to combat the spread of disease by introducing natural ventilation and Big Ass Fans in conjunction with UV lighting to kill the airborne pathogens.

According to Garret Gantner, a project architect with the MASS Group, who, along with several global health organizations, took on the task of designing and building a hospital for the residents of Butaro, “Tuberculosis rates are fairly high, and health centers have too often been the culprits in spreading airborne diseases due to poor ventilation in their facilities,” he said.


Included in final blueprints for the 65,000-sq-ft clinic were outdoor walkways, al fresco waiting rooms, and large windows strategically placed on opposing walls to aid in air circulation along with seven 12-ft large-diameter fans.

“Using [large diameter, low speed] fans allows us to have only one or two fans per ward, running them at speeds low enough that it will not make people feel cold,” said Gantner.

In addition, these fans are engineered with very small motors, drawing only a fraction of the amperage of the numerous small fans originally specified for the project. On average, each fan pulls less than 20W. The facility is run on 100% hydroelectric power from a newly constructed dam located one mile from the facility.

The idea to use fans along with UV lights was developed in conjunction with an infectious disease specialist at Partners in Health. In order to determine the number of fans necessary to meet or exceed WHO guidelines, several factors were taken into consideration per the designers’ requirements.

“The design team supplied a minimum air turnover rate,” said Christian Taber, senior applications engineer with the Big Ass Fan Company. “We measured air velocity at occupant level with the fans at the design mounting height to determine the maximum speed the fan could operate without causing a draft. We then measured the airflow rate of the fan at that operating speed and determined the minimum number of fans to meet the design air turnover rate requirement for each space.”

There is a series of UV lights installed around the wards and public areas where diseases are most likely to be transmitted.  The fans help draw air up, pass it over the UV lights, and ultimately ventilate it through the louvers on the windows.


With the exception of the fans, the clinic operates entirely on natural ventilation, meaning they have no A/C, heat, or ductwork. It is required that the fans remain on 24 hrs/day to produce an adequate number of air changes per hour.  It was imperative that the fans circulate the appropriate amount of air, provide quiet operation, and did not create a draft, which would discourage people from turning them off.

Beyond hospital settings, industrial, educational, and commercial buildings benefit from the use of large diameter, low-speed fans as well to help reduce or eliminate moisture and mold buildup and maintain acceptable IAQ levels. According to the Center for the Built Environment, temperature and air quality are the most important factors when considering comfort and productivity. Whether aiding ventilation, providing comfort, and helping to combat the spread of disease, large diameter, low-speed fan technology addresses IAQ issues through the simple act of air circulation.ES