Solar radiation is an interesting heat source for applications requiring a limited amount of energy, such as pre-heating cold fresh air used in venting livestock barns. The objective of this study was to evaluate the energy recovery efficiency of a solar air pre-heater consisting of an unglazed perforated black corrugated siding where the incoming fresh ventilation air picks up heat from its face and back. Installed on the southeast wall of two broiler barns located 40 km east of Montreal, Canada, the performance of solar air pre-heaters was monitored over 2 years. Sensors inside the barns monitored the temperature of the ambient air, that pre-heated by the solar collector and that exhausted by one of the three operating fans. An on-site weather station measured ambient air temperature, wind direction and velocity and radiation energy absorbed on a vertical plane parallel to the unglazed solar air pre-heaters. The measured vertical solar radiation value was used to evaluate the heat recovery efficiency of the unglazed solar air pre-heaters. Using data from the Varennes Environment Canada weather station located 30 km northwest, the solar sensors were found to measure the absorbed solar radiation with a maximum error of 7%, including differences in exterior air moisture. Unglazed, the efficiency of the solar air pre-heaters reached 65% for wind velocities under 2 m/s, but dropped below 25% for wind velocities exceeding 7 m/s. Nevertheless, the unglazed solar air pre-heaters were able to reduce the heating load especially in March of both years. Over a period starting in November and ending in March, the solar air heaters recovered an energy value equivalent to an annual return on investment of 4.7%. (C) 2011 Elsevier Ltd. All rights reserved.