The Unico System is a small duct central heating, air conditioning and ventilation system manufactured by Unico System International Limited (USIL), headquartered in Wales. The product has been on the market in the United States and Canada for the past 20 years, and over 250,000 of these systems have been installed there. The system has been profiled in numerous North American magazines and media outlets, most prominently on the television programme This Old House.