A Turbine Ventilator is a device based on direct combination of a wind turbine and extract fan. Turbine Ventilators are attractive replacements for electrical fans in terms of using renewable energy. They are commonly used in attic, loft and rooftop spaces to facilitate ventilation in buildings at both domestic and industrial level. This study presents a performance testing of four commercial turbine ventilators on a specifically designed test rig. The measurements of their ventilation rates and rotational speeds are taken at different wind speeds and compared with a simple open column and two standard vent hats.