Choosing and Installing Replacement Windows

Compare the pros and cons of partial versus full window replacement.

It's usually pretty easy to tell when your home needs new windows. You can see the drafts blowing the curtains, water damage is clearly visible, or frost is present on the inside layer of glass during the winter. What may not be so apparent; however, is what replacement window option best suits your needs, and what installation methods may pose potential headaches for you and your contractor.

There are basically three different replacement options: sash replacement, frame-and-sash replacement and complete unit replacement. Each has its benefits and drawbacks, and each carries its own installation quirks.

Sash Replacement

Sash replacement is a good option if the window frame is in good condition with no signs of water damage and the opening is still square and true. These are installed by removing old sashes and parting stops and installing new jamb liners. Most replacement sashes are compression-fit into the liners, making an airtight seal. This is the least expensive way to upgrade energy efficiency; there is no need to disturb trims or casings. However, the overall performance may fall short of other two options, and the new look may make the frame and sash appear too bulky.

"You can get virtually any glazing package with sash replacements that you could on any complete unit," says Brad Oberg, chief technology officer at IBACOS Inc. (www.ibacos.com), an architectural and engineering consulting firm in Pittsburgh. "There's no real sacrifice in performance with these units or the frame-and-sash units, but there may be in aesthetics for some people."

Sash-and-Frame Replacement

Sash-and-frame replacement can work well if the windowsill is showing signs of moisture damage or air is leaking between the sash and frame but everything else is in good shape. Typically, a single unit is fit into existing jambs and against the interior or exterior stops, then screwed or nailed into the jambs. These are the most expensive units to buy, but homeowners save in reduced labor costs. However, this option can reduce the daylight opening much more significantly than sash replacement.

Complete unit replacement — basically a new window with new flashing, sealants, caulking and insulation — is the best option for significantly compromised or damaged windows and openings. Requiring removal of old casings and trim, it often causes significant disturbance to interior and exterior finishes and siding. Although this may seem like the most invasive method, with proper installation you will get the best performance of all three options.

When it comes to choosing quality windows for a home, Brad recommends that homeowners look at these key areas:

  • A sturdy frame with multiple chambers (with vinyl and composite frames) for support and thermal resistance and reinforced corners (fully welded on vinyl units, not simply sealed).
  • The water management system should depend on flashing rather than caulking.
  • Installation aids such as adjustable screws on jamb liners to fine-tune the frame squareness.
  • All hardware and mechanisms are strong and well-attached.
  • Identify the weep system (typically on the bottom edge of the frame) and ensure it will drain moisture outside the particular siding system where it will be applied.
  • Smooth, easy-to-operate sashes.
  • Tilt sashes for easier cleaning and maintenance.
  • Any accessories such as between-the-glass blinds, snap-in grilles and screens should be durable and won't negatively affect the look of the window. Additionally, Brad urges homeowners to buy the best windows they can afford, even if it means doing a whole-house replacement in two or three stages rather than all at once.

Framing Options

Just as in replacements, there are different options available for framing:

Vinyl. Typically the least expensive, virtually maintenance free, only available in light colors (dark colors absorb too much heat from the sun and warp).

Fiberglass/composite. More expensive than wood or vinyl, but more durable as well. Requires virtually no maintenance, and can be painted any color, with faux woodgrains also available.

Wood. A popular choice for aesthetics, typically only a little more expensive than vinyl, requires diligent maintenance, can take any stain or color and available in many species.

Aluminum clad. Typically the most expensive but maintenance free, wood exteriors can be stained to match existing décor, while aluminum exteriors can take almost any color. May not be suitable for coastal environments where saltwater is a concern.

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