Installation Guide: Window Balance Replacement & Repair
Preserving Historic Wood Windows with Modern Solutions
Today’s homeowners value the quality craftsmanship of original wood sash windows. Rather than replacing these beautiful architectural elements with aluminum or vinyl alternatives, many are choosing restoration. In fact, numerous historic districts now require maintaining or authentically replacing original windows to preserve neighborhood character.
Why Preserve Wood Windows?
Wood provides superior insulation compared to modern materials, though traditional single-pane glass remains a weak point for energy efficiency. Fortunately, you can improve performance by:
- Retrofitting existing frames with new sashes
- Installing double-pane glass
- Adding UV-protective window films
Important safety note: When upgrading window glass, always adjust the balance mechanism to properly support the increased weight. Undersized balances can lead to unexpected sash drops, potentially causing injury.
The Timeless Benefits of Double-Hung Windows
Double-hung windows experienced popularity for centuries (through the 1960s) thanks to their natural ventilation design. Opening both top and bottom sashes creates convection airflow—cooler air enters through the bottom while warmer air escapes from the top. This practical feature remains relevant today:
- Reduces energy costs in regions with cool evening temperatures
- Provides effective ventilation without mechanical systems
- Complements classic architectural styles
Repair Options for Traditional Windows
Repairing Lead Weight Balance Systems
In homes built before the 1920s, window sashes typically operated using a pulley and weight system. These weights—usually lead or brick—counterbalanced the sash weight for smooth operation. The cotton ropes connecting these components generally required replacement every 20 years due to normal wear.
Step-by-Step Rope Replacement:
- Access the weights – Look for an access slot in the window frame or carefully remove interior/exterior molding
- Use a sharp knife to score paint along molding seams to prevent damage
- Gently remove molding from both sides
- Retrieve the counterweight from inside the wall cavity
- Remove old rope – Cut away deteriorated rope, noting the attachment method
- Observe any specialized knots or pulley arrangements
- Document the configuration for accurate restoration
- Install new rope – Replace with similar thickness rope (different sizes may jump the pulley)
- Consider nylon-blend options for extended durability
- Replicate original knots and routing pattern
- Reassemble components – Replace moldings, fill cracks, and repaint
- When properly installed, this repair can last decades
Modern Alternative: ACME® Side Mortise Sash Balances
For those seeking an updated solution, ACME® side mortise sash balances (also called tape balances) offer an excellent alternative to traditional pulley systems. These retractable spring balances use a metal strip wound into a contained unit that often fits into the same opening as the original pulley.
Installation Process:
- Measure and select – Remove and weigh the sash
- Choose the appropriate ACME® mortise weight size
- Add a few pounds for safety margin
- Remember each side carries half the total weight
- Prepare the frame – Remove the original pulley from the mortised slot
- Compare the ACME® mortise with the existing slot
- Adjust opening size if needed using a hammer and chisel or drill
- Secure the balance – Attach ACME® mortise balances to the frame with screws
- Carefully extend the tape (don’t release suddenly—it may damage the spring)
- Connect the tape to the window using the included hook
- Repeat on the opposite side
- Complete installation – Set the sash back into the window
- Replace stop molding and touch up paint as needed
Your ACME® double-hung window spring mortise balance will provide decades of reliable service while preserving the historical integrity of your windows.
Energy-saving tip: Some homeowners choose to add insulation to the weight pocket area when switching to mortise balances. This requires removing window casing or trim but can improve overall energy efficiency.
