Lowell Window Replacement: Bay & Bow, Double-Hung & Casement Windows

A bay is three windows set at angles, usually a fixed center pane between two operating units; a bow is several narrower units in a gentle curve. Both project from the wall, so the job includes a seat or head board, support under the unit and a small roof or cap above it. That's why HomeGuide prices bays at $2,000 to $6,000 installed and bows at $3,000 to $8,000 or more, and why a bay or bow can take an installer the whole day.

See bay and bow windows in Lowell for angles, seat boards and what a cap adds to the price.

This choice changes both the price and how much of the old window stays. An insert (also called pocket replacement) slides a new window into the existing frame, so the interior trim and exterior casing stay put and the bill is lower. Full-frame replacement strips the opening down to the rough framing and replaces frame, sill and sashes, which is the answer when the old sill is soft or the frame is out of square. Ask the contractor to probe the sills at the measuring visit: a rotted sill under an insert just hides the problem.

See full-frame vs insert replacement for how each is measured and when Lowell's permit applies.

Two sashes that both slide, with modern versions that tilt in so the outside glass can be washed from the room. Replacing like with like keeps the look of a triple-decker or colonial facade. HomeGuide's installed range is $350 to $2,500 depending on size and frame.

See double-hung windows for tilt-in, single-hung and grille options.

A casement is hinged on the side and cranks outward; an awning is hinged at the top and tilts out from the bottom. A casement opens its full width, which helps both airflow and escape. They suit the spot over a kitchen sink where reaching up to lift a sash is awkward. Installed, HomeGuide lists casements at $400 to $3,000 and awnings at $400 to $2,000.

See casement windows for crank and push-out styles, or awning windows for sink, bath and stacked layouts.

A picture window doesn't open, which gives it the most glass for the money and the fewest moving parts to wear out. It's often flanked by two casements or double-hungs so the room still gets air. HomeGuide puts an installed picture window at $300 to $1,300. Glass in a panel beside an entry door has to be safety glass under Massachusetts law, so mention where the window sits when you call.

See picture windows for flanker combinations and transoms.

Horizontal sliders fit wide, short openings: ranch bedrooms, 1960s and 1970s additions, and spots above a counter. One or both sashes glide sideways on a track, so nothing swings into a walkway or a porch. HomeGuide's installed range is $300 to $2,300.

See sliding windows for two- and three-lite sliders.

A basement or ground-floor bedroom needs an emergency escape opening. The base code asks for 5.7 square feet of clear opening (5.0 at or below grade), at least 24 inches high and 20 inches wide, with the sill no higher than 44 inches. Cutting a new egress opening in a foundation means excavation, a bigger hole in the concrete and a window well, which is why HomeGuide puts an egress window at $3,000 to $7,000, or $6,000 to $8,000 with the well and excavation. Massachusetts relaxes the rule for single- and double-hung windows: 3.3 square feet of clear opening, at least 20 inches wide and 24 inches high, is enough.

For bedroom escape openings, see egress windows; for hoppers, glass block and rusted steel frames, see basement window replacement.

Wood is the traditional choice for Victorians and for houses where the trim and muntin pattern matter. It's also the costliest frame: HomeGuide lists wood at $800 to $3,800 a window installed, against $400 to $2,000 for fiberglass. Composite frames fall in a similar band at $400 to $2,300, and HomeAdvisor's averages run vinyl $550, composite $900, fiberglass $1,100 and wood $1,250.

Read more on wood windows (primed, clad, insert) or fiberglass windows and how they compare on price.

The number to read on the NFRC sticker is the U-factor, which measures heat loss through the whole window, frame included: lower is better. The energy code Massachusetts uses caps new and replacement windows at U-0.30 in climate zone 5, and ENERGY STAR's Northern zone asks for U-0.22 or lower. Argon is the usual gas between the panes, and it leaks out at about 0.5% a year; triple-pane adds a third layer of glass for HomeGuide's $450 to $3,000 a window, against $400 to $2,000 for double-pane.

See energy-efficient windows for the code, ENERGY STAR and Mass Save details, and triple-pane windows for when a third pane is worth it.