Window Rehabilitation

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Description

The amount of work required to rehabilitate the windows will depend on the starting condition of the windows. Before beginning this work, the window should be assessed as outlined within the Ensuring Success tab.

For windows that are generally good condition (square, with sashes that properly fit to the window frame, and no broken or missing glass), the following work would be recommended (this work is covered in detail by Davis 2007):

  1. Remove the sashes by removing the interior stops and parting bead of the window frame.
  2. Clean the frames and sashes of any flaking paint or other coatings that may impede the proper installation of gaskets and seals.
  3. Replace broken glass and repair or replace damaged frames, sills, or sashes (not specifically described in this guide). Other retrofit measures, including sash replacement, window insert replacement, or complete window replacement should be considered for severely deteriorated windows.
  4. Replace all loose or missing window glazing (not specifically described in this guide).
  5. Caulk and seal the corners and joints in the window frame. This includes all joints between the sill and jambs as well as between the casings and frames.
  6. Cut grooves into the sashes where new gaskets will be installed.
  7. Prime and paint the window frames and sashes.
  8. Install new gaskets around the perimeter of the sashes. V-groove type gaskets will likely work the best at the jambs and meeting rails, while bubble gaskets work well at the head and sill interface.
  9. Reinstall the sashes, meeting rails, and interior stops.

Recommended sealant location as part of window frame rehabilitation

Figure 1 - Recommended sealant location as part of window frame rehabilitation Reference

If weight pockets are to be retained, then cleaning and lubrication of the pulleys, replacement of the sash cords or chains, and balancing of the weights should be completed as part of the work.

The weight and balance system could also be abandoned and replaced with a spring-loaded tape balance. The weight pockets can then be insulated and sealed, improving the overall thermal performance of the window frame-to-rough opening interface.

Windows requiring more extensive rehabilitation such as re-glazing, replacement of rotten wood, or rebuilding of sashes are outside the scope of this guide. Other retrofit measures, including sash replacement, window insert replacement, or complete window replacement should be considered for severely deteriorated windows.

Ensuring Success

Wood window options for existing homes

Identifying Risks
Prior to any retrofit work being conducted, it is important that the following conditions of the building systems be reviewed:

  • Lead and other hazardous materials
  • Site conditions and project staging
  • Identification of water infiltration concerns
  • Identification of deteriorated or damaged materials
  • Identification of user comfort concerns

Contractor/Homeowner Safety

US EPA: Lead in Paing, Dust and Soil: Renovation, Repair Painting

OSHA: Fall Protection (if window work is to be done at height, from the exterior)

Lead and Other Hazardous Materials
Old wood windows and trim are a common location of lead paint in homes. Any work being completed on the window systems should follow all appropriate state and federal laws regarding handling of hazardous materials.

Site conditions and Project Staging
The home and site should be reviewed to identify impacts and potential risks with completing the work.

If the work is to be done for the exterior, scaffolding, lifts, ladders, or other means to access work areas may be needed. Work done at height may require fall protection be used. Proximity to adjacent property or vegetation may limit access or create unsafe work areas.  Exterior staged work may also damage existing landscaping or vegetation.

If the work is intended to be completed from the interior, consideration should be given to disruption of the occupant and clearances for moving equipment and materials into and out of the space. With any interior work there is always a chance of damage to interior finishes.  Appropriate planning and protection is required.

Identification of Water Infiltration Concerns
Windows, above all other enclosure systems, are a common location of water infiltration issues.  It is important to understand the various pathways for potential water infiltration, and identify current water leakage problems. While the details presented in this document are all intended to improve the moisture performance of the window assemblies, it is not intended to address all possibilities, and is not a replacement for inspection and evaluation of the performance of an individual window.  Existing problems should be identified, and the strategy chosen that will be most appropriate to address the concern. Window systems water leaks can be grouped into four general categories (Figure 1 below):

  1. Between the window frame and rough opening
  2. Through the joints in the window frame
  3. Between the window frame and the operable sashes
  4. Through the joints between the glass and the sash frames

Common window water infiltration pathways

Figure 1 - Common window water infiltration pathways Reference

Prior to any work being done, interior and exterior inspection and monitoring of the conditions of the building should be completed. Water staining, peeling paint or wall paper, and staining on trim or floor assemblies below window systems are indications of water infiltration and/or condensation. Leakage between the sashes and the frame and between the glass and the sash is usually marked by water staining on the interior window frame itself. Condensation on the window frames can also lead to staining of the interior finishes. It is important to monitor the questionable area to prevent a false diagnosis of the water management problem being experienced.

Leakage between the window and rough opening or through the joints in the window itself are typically contained within the wall assembly and may go unnoticed, or could manifest as staining and peeling paint below the window or damaged flooring.

Other problems such as water infiltration at the window head may be indications of failed or missing head flashing. However, other problems not associated with the window system may in fact be the cause of the water infiltration. Care must be taken to properly diagnose the infiltration pathway.

If it is a known recurring problem, then the infiltration problem must be addressed prior to or in conjunction with the window retrofit work.

If no obvious signs of water infiltration problems exist and the window elements and connection wall components are in good condition, no additional work may be needed. However, as stated above, water infiltration problems are often concealed within wall cavities with no outward signs. This becomes more of a concern if the window retrofit work is being done in conjunction with the addition of cavity fill insulation. With the addition of insulation to the wall cavities, water infiltration problems that previously may have had sufficient drying ability, may now lead to prolonged moisture accumulation. Prolonged moisture accumulation can lead to material deterioration. If there is suspected leakage, then further investigation, including but not limited to thermal scans, moisture content measurements, and cutting of investigation holes below window assemblies to look for signs of moisture problems would be recommended.

Unless the problem is obvious, it may be prudent to contact someone with experience with diagnosing water infiltration problems prior to proceeding.

Identification of Deteriorated or Damaged Materials
If damage to existing elements is noted, the materials should be removed and replaced as part of the retrofit. Certain elements will be more critical to the proper implementation of the chosen strategy.

Failed window sill with replacement window installed

Figure 2 - Failed window sill with replacement window installed Reference

The window sill is arguably the most important element of the window assembly, as water will drain downward by gravity either into the wall (e.g., hole through sill) or directly onto the wall (failure of the sill extension). For all proposed measures in this document excluding complete window replacement, the condition of the sill is critical to the performance of the measure. Cracked or rotting sills need to be replaced prior to any work being done.

The window frame including the exterior casings is the next most critical element. If the casing is deteriorating, its replacement may be warranted. This should not be confused with the exterior trim, which is often installed as a decorative element on top of the casing. 

Deteriorating trim may not affect the water management performance of the window however; it may be an indication of other problems and generally creates an aesthetic problem.

Failed window sill with replacement window installed

Figure 3 - Failed window sill with replacement window installed Reference

Depending on the measure being examined, the condition of the window sashes may or may not be a concern to the performance of the measure taken. For window rehabilitation, sash retrofit, or interior storm retrofit, the condition of the sashes is critical to the performance of the window.  For exterior storms, the sashes are more protected from the elements, and the condition is less important from a water management perspective, yet still critical from an energy and condensation resistance perspective. For sash replacement, window insert, or full window replacement, the condition of the sash is irrelevant, as they will be removed. For this reason, windows with severely deteriorated sashes may be better candidates for the latter retrofit measures.

Identification of User Comfort Concerns
As part of the initial review, associated comfort concerns relating to the window systems should be evaluated.  Window air leakage is a significant source of occupant comfort problems.  Unlike other common enclosure leakage pathways, window air leakage is commonly very direct, resulting in distinct drafts. 

Radiation effects from cool glass surfaces are another common comfort problem. This is more difficult to identify, as the tendency is to assume that the discomfort felt when near a window is from air leakage or drafts. This results in some misdiagnosis of the dominant function. A general recommendation is to increase the interior surface temperature of the window system to reduce the radiant heat transfer from the occupant to the window. This is commonly done by adding additional panes of glass (or films) to create an insulating air (or other gas) space between the layers.

Window Rehabilitation

This measure improves the existing performance of the window without significant modifications or additions to the window. This measure has practically no impact on the appearance of the window as the modifications are all concealed and minor.

Key points to consider when selecting Window Rehabilitation are as follows:

  1. Maintains both the interior and exterior appearance of the building. (This is an important strategy where historic preservation is required.)
  2. This work is best done in conjunction with other measure strategies, including interior and exterior approaches (such as the addition of interior and exterior storms).
  3. This work will not address any current condensation problems that may be occurring on the window system.
  4. If sash weights are maintained, other potential energy and durability considerations may not be addressed, such as air leakage and thermal conductance losses at weight pockets.
  5. Cost can be highly variable depending on the size, complexity, condition, and value of the windows.

Scope

Recommended sealant location as part of window frame rehabilitation

As summarized within the Ensuring Success tab, inspect the interior and exterior of the building, including each window, to identify impacts and potential risks with completing the work. Diagnose water and air infiltration pathways, and choose strategies most appropriate to address each leak. Add gaskets and seals at common air infiltration locations to improve the overall air tightness of the window assembly. Some methods are covered in detail by Davis (2007).

Training

Right and Wrong Images

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Presentations

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Videos

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CAD Images

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Compliance

ASTM E-2112-07

Standard Practice for Installation of Exterior Windows, Doors and Skylights. Available from ASTM. The standard covers fenestration product installation from pre-installation through post-installation procedures in new and existing construction.

2009 IECC

Section 101.4.3 Additions, alterations, renovations or repairs. Additions, alterations, renovations or repairs to existing buildings, building systems, or portions of buildings or systems must meet the requirements of the code as they relate to new construction.  Unaltered portions do not need to comply. Exceptions are included for storm windows installed over existing fenestration and glass-only replacements in an existing sash and frame. Section 402.3.6 Replacement fenestration. When some or all of an existing fenestration unit is replaced, including sash and glazing, the replacement unit must meet the U-factor and SHGC requirements in Table 402.1.1. *

2012 IECC

Section R101.4.3. Additions, alterations, renovations or repairs. Additions, alterations, renovations or repairs to existing buildings, building systems, or portions of buildings or systems must meet the requirements of the code as they relate to new construction.  Unaltered portions do not need to comply. Exceptions are included for storm windows installed over existing fenestration and glass-only replacements in an existing sash and frame. Section R402.3.6 Replacement fenestration. When some or all of an existing fenestration unit is replaced, including sash and glazing, the replacement unit must meet the U-factor and SHGC requirements in Table R402.1.1. *

2009 IRC

Section N1101.3 Additions, alterations, renovations or repairs. Additions, alterations, renovations or repairs to existing buildings, building systems, or portions of buildings or systems must meet the requirements of the code as they relate to new construction.  Unaltered portions do not need to comply. Exceptions are included for storm windows installed over existing fenestration and glass-only replacements in an existing sash and frame. Section N1102.3.6 Replacement fenestration. Where some or all of an existing fenestration unit is replaced with a new fenestration product, including the sash and glazing, the replacement unit must meet the U-factor and SHGC requirements of Table N1102.1.1. AJ102.4 Replacement windows. When an existing window is replaced, including the sash and glazing, the replacement must meet Chapter 11 requirements. AJ401.2 Door and window dimensions.  Minor reductions in the clear opening dimensions of replacement doors and windows that results from using different materials are allowed.*

2012 IRC

Section N1101.3 (R101.4.3) Additions, alterations, renovations or repairs to existing buildings, building systems, or portions of buildings or systems must meet the requirements of the code as they relate to new construction.  Unaltered portions do not need to comply. Exceptions are included for storm windows installed over existing fenestration and glass-only replacements in an existing sash and frame. Section N1102.3.6 (R402.3.6) Replacement fenestration. Where some or all of an existing fenestration unit is replaced with a new fenestration product, including the sash and glazing, the replacement unit must meet the U-factor and SHGC requirements of Table N1102.1.1. AJ102.4 Replacement windows. When an existing window is replaced, including the sash and glazing, the replacement must meet Chapter 11 requirements. AJ401.2 Door and window dimensions.  Minor reductions in the clear opening dimensions of replacement doors and windows that results from using different materials are allowed.*

*Due to copyright restrictions, exact code text is not provided.  For specific code text, refer to the applicable code. 

More Info.

Case Studies

None Available

References and Resources*

  1. Author(s): Wilson
    Organization(s): National Research Council Canada
    Publication Date: May 1960

    Document about condensation between the panes, on the inside surface of the outer glass of double pane windows.

  2. Author(s): EIA
    Organization(s): EIA
    Publication Date: January 2009

    Federal statistics about national energy consumption in residential homes.

  3. Author(s): Davis
    Organization(s): Fine Homebuilding Magazine
  4. Author(s): National Fenestration Rating Council
    Organization(s): National Fenestration Rating Council
    Publication Date: January 2010

    Standard providing a procedure for determining fenestration attachment product U-factors.

  5. Author(s): National Fenestration Rating Council
    Organization(s): National Fenestration Rating Council
    Publication Date: January 2010

    Standard for determining fenestration attachment product SHGC and visible transmittance.

  6. Author(s): Brown
    Organization(s): National Research Council Canada
    Publication Date: January 1997

    Research study dcribing an evaluation of selected windows undertaken by IRC researchers at Ottawa’s Laurier House (now being used as a museum) to determine their effectiveness in controlling condensation.

  7. Author(s): Baker
    Organization(s): BSC
    Publication Date: December 2012

    Document providing information and guidance about rehabilitating, retrofitting, and replacing wood window assemblies in residential construction.

Last Updated: 10/01/2013

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