Restore when the wood is sound and the joints are tight, because old-growth sash are denser and more rot resistant than anything milled today. Replace when bottom rails have gone soft or the mortise and tenon joints have opened. Restoration plus a low-E storm costs $400 to $900 per opening.
There is a real argument for keeping original wood windows and it is not purely sentimental. Sash built before roughly 1940 were made from old-growth lumber with tight growth rings and high heartwood content, which is more dimensionally stable and far more rot resistant than the fast-grown lumber available today. A well-maintained sash from 1910 can outlast a replacement window installed in 2026.
The argument stops being valid at a specific and identifiable point. Here is how to find it.
Restore if, replace if
| Condition | Restore | Replace |
|---|---|---|
| Wood sound when probed at the bottom rail | Yes | |
| Bottom rail soft or crumbling | Yes | |
| Mortise and tenon joints tight | Yes | |
| Joints opened, sash racks when lifted | Yes | |
| Glazing putty failed but wood is fine | Yes, reglaze | |
| Repeatedly repaired with filler | Yes | |
| In a historic district | Yes, usually required | |
| Muntins loose but intact | Yes | |
| Significant sections missing or rotted through | Yes |
What restoration actually involves
- Removing the sash and stripping old paint and failed glazing putty.
- Consolidating any minor soft spots with epoxy consolidant, and rebuilding small losses with epoxy filler.
- Reglazing the panes with fresh putty and points.
- Repairing or replacing failed joints where possible.
- Priming and painting all surfaces, including the top and bottom edges that are usually skipped.
- Installing new weatherstripping in the jamb and at the meeting rail, which is where most of the air leakage is.
- Repairing or replacing the sash cords, pulleys and weights on a traditional double hung.
- Fitting a low-E exterior storm window to create the second air space.
How restored windows actually perform
This is the part people are skeptical about and the numbers are better than expected. A single pane sash by itself performs poorly, roughly equivalent to one layer of glass with substantial air leakage around a sash that has no weatherstripping left. Add proper weatherstripping and you eliminate most of the air leakage, which is where a large share of the actual heat loss was. Add a low-E exterior storm and you create a second sealed air space, which is the same principle a double pane unit uses. The combined assembly approaches the performance of a modern double pane window. It does not match a good triple pane unit, and you keep managing two layers, but the gap is much smaller than the marketing for replacement windows suggests.
Cost comparison
| Approach | Cost per opening | What you keep |
|---|---|---|
| Restore sash, weatherstrip, add low-E storm | $400 to $900 | Everything original |
| Sash replacement kit in existing frame | $250 to $700 | Frame, sill, interior trim |
| Insert replacement window | $450 to $850 | Frame and trim only |
| Full frame wood replacement | $900 to $1,800 | Nothing |
| Full frame vinyl replacement | $700 to $1,200 | Nothing |
Restoration is labor-intensive, so its cost is driven by condition rather than by size. Badly deteriorated sash can cost more to restore than to replace.
Ranges reflect typical Capital Region projects and are for planning only. Every Sundog quote is written, itemized, and free.
Frequently asked questions
Are old wood windows better than new ones?
The wood is better. Old-growth lumber with tight growth rings and high heartwood content is more stable and more rot resistant than anything commercially available now. The glass, the weatherstripping and the hardware are worse. Restoration addresses all three of those while keeping the good part.
How much does window restoration cost?
Typically $400 to $900 per opening in the Capital Region including a low-E storm window, though it varies more with condition than with size because the cost is mostly labor. Heavily deteriorated sash can exceed what a replacement would cost, which is the point at which restoration stops making sense.
Do restored windows perform as well as replacements?
A restored, weatherstripped sash with a low-E exterior storm gets close to a modern double pane unit. You do not get tilt-in cleaning or a single-assembly convenience, and you still manage two layers seasonally. For thermal performance, the gap is much smaller than replacement window marketing implies.
How do I tell if my sash are worth restoring?
Probe the bottom rail and the lower corners of the stiles with a screwdriver, since that is where water collects and rot starts. Sound wood resists firmly. Then lift the sash and see whether it racks or feels loose, which indicates the mortise and tenon joints have opened. Sound wood plus tight joints means restore.
Do I have to restore if I am in a historic district?
Often, effectively yes, because full replacement on street-facing elevations is frequently not approved in Albany, Troy, the Schenectady Stockade or Saratoga Springs review areas. Restoration plus storms is the path that most reliably gets through review, and it also happens to be the approach that preserves the most value in the house.
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