RELIABILT Replacement Windows
RELIABILT replacement windows fit inside existing window frames without exterior construction. The most common window upgrade.
RELIABILT replacement windows are designed to fit inside your existing window frame, making them the simplest upgrade option. No exterior siding work, no new framing, no changes to interior trim. You remove the old sashes and install the new insert window in the existing frame. Available in single hung, double hung, and sliding styles from $89 to $300+. This is the right choice for upgrading old, drafty, or single-pane windows.
How Replacement Windows Work
| Step 1: Measure | Measure width at top, middle, bottom. Measure height at left, center, right. Use smallest of each. Deduct 1/4" for clearance. |
| Step 2: Remove | Remove old sashes, stops, and weatherstripping. Leave the existing frame in place. |
| Step 3: Install | Set new window in opening, shim for level and plumb, screw through frame flanges, insulate gaps with low-expansion foam. |
| Step 4: Finish | Replace interior stops, caulk exterior, test operation. |
How to Choose a Replacement Window
Sizing: Accurate measurement is critical for replacement windows. Measure the width between the side jambs at three points (top, middle, bottom) and the height between the sill and head jamb at three points (left, center, right). Use the smallest measurement for each dimension, then deduct 1/4 inch for fitting clearance. An incorrectly sized window cannot be returned once the protective film is removed.
Window style: RELIABILT replacement windows are available as single hung, double hung, and sliding. Match the style you currently have for the most straightforward installation. Switching styles (for example, from double hung to sliding) is possible if the rough opening dimensions work, but may require trim modifications.
Energy ratings: Replacement windows deliver the biggest energy savings when you are upgrading from single-pane glass. Even upgrading from older dual-pane to modern Low-E dual-pane can reduce energy costs. The 3500 Series with argon fill provides the best thermal performance and qualifies for Energy Star across all US climate zones. Check whether your state or utility offers rebates for Energy Star-rated replacement windows.
Frame condition check: Before ordering, inspect your existing window frame for rot, water damage, or structural issues. Replacement windows rely on the existing frame for support. If the frame is damaged, you need new construction windows with a full frame replacement instead.
Glass area trade-off: Because a replacement window fits inside the existing frame, the visible glass area is slightly smaller than the original window. This is normal and typically amounts to about 1/2 inch less glass on each side. For most homeowners the difference is not noticeable, but it is worth knowing before you compare side-by-side with a neighbor's new construction installation.
Common Problems and Fixes
Condensation on the interior glass: Interior condensation on replacement windows usually means your home's humidity is too high for the outdoor temperature. This is common right after installation because the new windows seal much tighter than the old ones, trapping more indoor moisture. Run exhaust fans in kitchens and bathrooms, and consider a dehumidifier. If condensation appears between the panes, the IGU seal has failed and the glass needs replacement under warranty.
Drafty after installation: Air leaks around a newly installed replacement window typically indicate gaps between the insert frame and the old frame that were not properly insulated. Remove the interior trim, check for gaps, and fill with low-expansion foam. Use only low-expansion foam rated for windows and doors. Standard expanding foam can bow the frame and interfere with sash operation.
Sash balance failure: If the sash drops when released or is hard to raise, the balance mechanism has worn out. This is more common in double hung models because both sashes use balances. Match the weight rating and length of the original balance when ordering a replacement from Lowe's.
Difficult to open or close: If the window operated fine at installation but became stiff over time, dirt in the tracks is the likely cause. Clean and lubricate with dry silicone spray. If the window was always stiff from day one, the frame may be slightly out of square due to improper shimming during installation. Re-shim to correct.
Exterior condensation: Dew on the outside of the glass is normal with modern Low-E replacement windows and indicates the coating is working. It is especially common in fall and spring mornings. This is not a defect and evaporates as outdoor temperatures rise.
Noise from the old frame: Replacement windows sometimes transmit more wind noise than expected because the existing frame may have gaps behind the interior trim. Remove the trim, fill any voids with low-expansion foam, and reinstall. This both reduces noise and improves energy performance.
Maintenance Guide
Cleaning vinyl frames: Wash with mild soap and warm water using a soft cloth or sponge. Avoid bleach, acetone, or abrasive cleaners that can damage the vinyl surface. For mold or mildew on the frame (common in humid climates), use a solution of one part white vinegar to three parts water. Clean frames at least twice a year.
Lubricating tracks and hardware: Vacuum sash tracks twice a year to remove dust and debris. Apply dry silicone spray to the tracks and any pivot points on the tilt hardware. Do not use petroleum-based lubricants. For replacement windows specifically, also check that the cam locks and keepers are aligned properly, as settling can shift them slightly over the first year.
Replacing weatherstripping: The weatherstripping on replacement windows seals the sash against the frame. Over several years, it compresses and loses effectiveness. Peel off the old strip and press in compatible self-adhesive weatherstripping. For the meeting rail on double hung units, use the specific profile designed for that location to maintain a tight seal.
Re-checking the installation seal: Once a year, inspect the caulk between the replacement window frame and the old window frame, both inside and outside. This joint is critical because it is the primary barrier against air and water infiltration. Re-caulk any gaps with a flexible sealant rated for exterior use.
Screen and hardware care: Remove the screen annually, rinse with water, and check for tears. Inspect the sash locks, tilt hardware, and balances. Tighten any loose screws and lubricate moving parts with dry silicone. Catching small issues early prevents costly repairs later.
Seasonal checks: In fall, verify that all windows close and lock securely before heating season. In spring, open each window to confirm smooth operation after months of being closed. This simple habit catches problems like stuck sashes or deteriorated weatherstripping before they affect comfort or energy bills.
Frequently Asked Questions
What is the difference between replacement and new construction windows?
Replacement windows (also called insert windows) fit inside your existing window frame. New construction windows have a nailing fin that attaches directly to the wall studs and require the old frame to be completely removed. Use replacement windows when your existing frame is in good condition. Use new construction when the frame is damaged or when building a new wall.
Can I install RELIABILT replacement windows myself?
Yes, replacement window installation is one of the more accessible DIY window projects. The old sashes are removed, the new insert is placed in the existing frame, shimmed, screwed, and sealed. Basic tools are needed: tape measure, level, drill, shims, low-expansion foam, and caulk. Most homeowners can install one window in 30-60 minutes after the first one.
Will replacement windows reduce my energy bills?
If you are upgrading from single-pane windows, expect a noticeable reduction in heating and cooling costs. Dual-pane Low-E glass blocks heat transfer far more effectively. The exact savings depend on your climate, the number of windows replaced, and your current energy costs. Homes in extreme climates (very hot or very cold) see the biggest return.
The 3500 Series with argon fill provides the best efficiency. Check whether your state or utility offers rebates for Energy Star-rated replacement windows, which can offset part of the cost.
For new construction where no frame exists, see new construction windows instead. Replacement windows use existing interior trim, so you typically do not need new moulding. Check warranty coverage and customer reviews.
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