Spiral Pipe of Texas manufactures a wide range of internally insulated rectangular duct products. Insulation is necessary for most HVAC duct applications, ducts internally insulated by the manufacturer offer consistent quality, greater material options, better appearance, liner protection, and reduced field labor. There are several methods and options for insulating rectangular ducts, we strive to produce products that not only meet the highest requirements of performance and function, but also utilize materials and methods that are environmentally conscious.