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Ensure Proper Installation of Replacement Windows

  • A window can only perform well if properly installed. Quality installation is critical for an airtight fit and a continuous water barrier to prevent drafts, water damage and condensation. The complexity of the installation depends on whether you are considering complete window replacement or inserting windows or sash kits within the existing frame. Make sure to follow manufacturers' recommendations on whether the particular installation requires trained professionals or whether do-it-yourself is an option.

    Finding Quality Installers

    The first place to inquire about quality installers is the manufacturer from whom you are purchasing the windows. Each manufacturer has detailed installation requirements and specifications for their products and may have recommendations of in-house installers and programs, 3rd party installers, or installation certification programs.

    There are standards for proper window installation, and installers are well advised to follow these along with the manufacturer's installation requirements. The most prominent of these standards is ASTM Standard E 2112 exit disclaimer. Installers who are certified through nationally recognized certification programs or through the training programs offered by manufacturers are likely to be familiar with this standard.

    Window manufacturers may have certification programs for installers of their own products. Installers may also be certified by nationwide programs such as:


    Ultimately, finding trusted installers is a case-by-case decision. References may help with recommendations.

  • Some Installation Basics for Window Replacement

    1. Always follow manufacturer's installation guidelines and specifications.
    2. Install level, plumb, and square.
    3. Install water tight: water must be prevented from penetrating behind the water control system of the wall. Different techniques apply to different water control systems:
      • Surface barrier system (masonry, concrete or brick with no cavities): the window frame must be carefully joined with the surface barrier because no water must penetrate this barrier;
      • Drainage membrane system (house wrap or building paper behind exterior cladding material such as siding, brick veneer, or stucco): the window must be installed so that any water that gets behind the cladding is drained down and out over the drainage membrane.
    4. Allow movement and thermal expansion (¼" to ½ tolerance around the frame)
    5. Seal it up: Maintain the integrity of any air barrier and vapor retarder used in the wall system and seal all gaps around the window frame with caulk. Insulate all voids with foam or batt, but only use low-expansion foam to avoid pressure that could distort the window frame.