Pella ThermaStar is a line of basic, inexpensive vinyl windows sold exclusively at Lowe's and qualified Pella dealers. If you're looking for standard windows—for new construction or remodeling, not replacement windows—and don't need a lot of bells and whistles, ThermaStar might be a good fit for your project.
Window Types and Options
The ThermaStar line includes single-hung, double-hung, casement, awning, and slider windows as well as sliding patio doors. They also come in combination windows (which combine two standard-size windows into one unit), special-size/shape windows, and bay or bow windows. The one notable exception is hinged patio doors, which tend to be exclusive to high-end product lines. You're likely to find several of the basic types in standard sizes on the shelves at Lowe's, but for non-standard sizes or windows with any special features, you'll probably have to order them.
Keep in mind that availability of window types, sizes, and options varies by geographic location. ThermaStar windows that are sold in Pella's Eastern territory may not be available in their Western territory. Any local ThermaStar retailer or dealer will be able to give you details on what's available in your area.
All ThermaStar windows are double-paned and have argon gas between the panes. Argon is an inert gas that helps reduce heat transfer through the window. Most thermal windows—that is, double- or triple-paned—have argon or other inert gasses between the panes because they resist heat transfer better than air. One optional energy-efficiency upgrade is a Low-E coating that reduces heat gain, or the amount of heat that is allowed through the window from the outside.
ThermaStar windows and patio doors come only in white.
New-Construction, Not Replacement
These are not replacement windows. Rather, they have an integrated nailing fin on the outside that allows you to nail the window directly to the house sheathing. This type of window goes in before the siding is installed.
If you're replacing your siding at the same time as the windows, or you're building a new house or addition, ThermaStar is an appropriate type of window. If you're simply taking out your old windows and installing new ones without changing the siding or window trim, you're in the market for replacement windows. These have no nailing fin and attach to the inner window frame. Other than the presence or lack of a nailing fin (also called a nailing flange), new construction and replacement windows are the same.
ThermaStar tends to be a rather tepid offering from Pella. While the line includes basic modern features, such as double-glazing, optional Low-E coating, and insulating gas, consumers report issues such as problems with locking mechanisms and trouble sliding the window sashes. Also, the overall "fit and finish" of ThermaStar windows is not stellar. The corner welds tend to be very prominent, and the overall build quality is decent, but certainly what you'd expect for a budget product.
The chief advantages of ThermaStar appear to be its availability (grab a window from Lowe's and install it the same day, rather than waiting 6 weeks for delivery); the opportunity for self-pick-up (saving delivery charges); and low prices. The energy performance of the ThermaStar line is pretty good for the price. To compare energy performance, look to the U-factor, Solar Heat Gain Coefficient, and Visible Transmittance ratings.