THV Compozit - Who We Are

THV Compozit Windows & Doors, Where Innovation Creates Value

THV Compozit Windows & Doors is a family owned and operated company. Since our establishment in 1984 by Al Leingang, THV Compozit, previously named Thermal Line Windows, has grown to be a leader in the ever-changing world of today's remodeling industry, manufacturing, selling, and installing quality replacement windows across the United States.



Our top-of-the-line replacement windows are manufactured in a 65,000 sq. ft. factory that is located in Mandan, ND –home to one of the coldest cities in North America, making it an ideal setting to design an energy efficient window. Our factory contains the latest in design, engineering, and manufacturing equipment which enables us to develop THV Compozit Window and Door Systems that continue to keep us on the forefront of quality and innovation in the window and door industry.



In 2005, Charles L. Smith, current CEO, became a major shareholder in THV Compozit Windows & Doors with the knowledge that the company was well-known throughout the Midwest for having a unique energy efficient window. Smith brings a wealth of knowledge and expertise to THV Compozit Windows & Doors, enabling the company to produce windows that not only look and operate great, but also meet customers' precise needs.

A second generation to the window industry, Smith grew up around glass and screen repair working in his father's shop after school. As his father was one of the first window dealers to ever handle replacement windows, Smith gained an abundance of knowledge from his experiences at an early age. In 1972, at age 16, Smith was working on job sites replacing windows, gaining installation experience, and engaging with customers. This same year, accompanied by his father, Smith was involved in the design of a new state-of-the-art replacement window, the Thermal Guard window. Ten years later in 1982, he started his own retail company, as well as helped design the new next generation replacement window, the Bristol Window, sold by Winchester Industries. Both windows were way ahead of their time depicting the triple pane structure, what is known today as state-of-the art. However, THV Compozit Windows & Doors has been making Triple Insulated Glass for more than 30 years.



We are committed to providing you with the highest standards so you can obtain the low-maintenance lifestyle you prefer

At THV Compozit Windows & Doors, our reputation depends on our everlasting commitment to quality and customer service. To assure you peace of mind, we use state-of-the art materials, precision engineering, and proven construction methods for windows that last. Since we can assist in all phases of decision making, specification, and production, we can make sure that your THV Compozit Window and Door System will improve the value, comfort, and appearance of your home.


When it comes to home expenditures, THV Compozit replacement windows rank as one of the best returns on your investment. Because the addition of new Compozit windows can save fuel consumption while also increasing your home's value substantially, you should think of new replacement windows as an investment that will enhance your living.



  • Pioneer in Compozit Windows since 1989
  • Design, manufacture and installation of replacement windows since 1984
  • 50 year transferrable warranty
  • Independent laboratory tested and certified products
  • Founding member of the NFRC (National Fenestration Rating Council)
  • Energy Star qualified products
  • Window & Door Top 100
  • 30 years experience in making Triple Glass
  • Proud member of the NDSC (North Dakota Safety Council)
  • Employer Supporter of the Guard and Reserve (ESGR)
  • 1995 Lineal Sales Award from Complast
  • 1998 Fabricator of the Year Award (For Outstanding Sales and Marketing in Compozit Window Technology)
  • P.H. Tech True Performer Award Winner, 2001-2002

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