The Pella 450 and 850 series is a collection of branded windows and doors manufactured by the Pella Corporation. Pella is a family-owned corporation, which began in 1925, in Pella, Iowa. As of September 2011, Pella ranks as the second largest manufacturer of windows and doors in the world. The 450 and 850 series are sold under the brand trade names of Pella 450 ProLine and the Architect Series 850.
The Pella 450 series is called the "ProLine." It includes sliding patio doors, awning-style windows, casement, double-hung windows and half-circle windows. The 450 ProLine series offers three windowpane grill patterns to choose from, eight interior wood stain colors, and the option of windows painted with a white prefinished that owners could paint themselves to match and compliment the homes exterior and interior colors and décor.
The Pella 850 series is called the "Architect 850 Series." In addition to awning-style windows, casement, double-hung windows and half-circle windows, the 850 series includes French patio doors. The 850 series is more refined and upscale, with mahogany, alder, Douglas fir and pine wood finishings. Customers can select from 27 exterior colors to match and coordinate with the exterior of their home, along with a wide variety of grille designs and patterns to simulate the look of divided light as it filters through the windowpanes. Like the 450 series, the 850 series offers eight interior stains to choose from or the option of a basic white prefinished window for customization.
The Pella Corporation exclusively manufactures the 450 and 850 series. Each series provides customers with many options for window and door styles and features. For example, double-hung windows allow you to open the window from the top and from the bottom. Casement windows are hinged at the side so you can open them outwards to the outdoors instead of inside the room. Awning-style windows are hinged at the top and open outwards from the bottom. The 450 and 850 series are sold at Lowe's home improvement stores and can be ordered from select retailers.
The 850 line provides far more choices in terms of window grille styles, wood finishes, interior wood stain colors and exterior color possibilities, compared to the 450 series. The 850 series also includes French sliding glass doors with hinges, while the 450 series only has conventional sliding doors. Window and door glass are measured for energy efficiency in terms of their U-factor, which is a numeric value assigned by independent testing laboratories. The U-factor measures the rate of non-solar heat loss or gain of the window or door. The lower the U-factor, the greater a window's resistance to heat flow. The 450 series windows and doors have U-factors that range from 0.32 to 0.35, and the U-factor for the 850 series ranges from 0.35 to 0.39, according to ratings published as of September 2011 by Efficient Windows Collaborative.org, which is a non-profit partnership between the University of Minnesota, the Center for Sustainable Building Research, the Alliance to Save Energy, and Lawrence Berkeley National Laboratory.