Short answer. A draft near the centre of an old double-hung window does not automatically mean the weatherstrip at its meeting rail failed. There may be an air path between two moving sash, but cracked glazing putty is a different defect around the glass edge and can admit moisture to wood joints. Diagnose the location before choosing a gasket. [NPS9, PDF p. 2, Physical Evaluation and fig. 2]
Two boundaries in one photograph
Take one photo showing both meeting rails and the latch, then a second showing the glass-to-wood glazing perimeter nearby. On a sketch, draw the rail-to-rail joint as line A and the pane-to-putty/rabbet boundary as line B. If discomfort is near the middle, mark only its perceived location; do not declare line A or B to be a proven air leak. NPS calls for separate condition checks of the sash, glazing, frame, sill and hardware. [NPS9, PDF p. 2, Physical Evaluation]
A deteriorated putty line can appear cracked, loose or missing. NPS explains that exterior putty failures may permit water saturation, and back putty helps prevent condensation running into wood joinery. Those are moisture and glazing-condition concerns, not proof of a particular weatherstrip profile. [NPS9, PDF p. 2] Conversely, when opposing rails are visibly separated or a sash lock does not seat normally, a meeting-rail condition assessment is appropriate; that does not prove which strip should be fitted.
Three safe observation moments
Record how the window looks when resting normally closed, how the latch sits without forcing it, and what changes during a separate period of wind or rain. Note whether a water stain appears after rain versus only a feeling of cold air during wind. If the meeting rails close unevenly, photograph the whole sash—not only the small gap—because the underlying issue may be geometry or worn hardware. Do not press a lit flame near curtains, break glazing seals, remove putty, or force a latch to 'prove' a draft. Photograph instead.
Compare the notes with a nearby window of the same design, if available. Differences may reveal missing hardware or a previously added strip, but neither comparison establishes originality. If glass is loose, wood feels unstable or water continues to enter, arrange a professional assessment rather than treating tape as a structural fix.
The repair-first sequence
A professional may need to address water entry or missing glazing compound, review sash alignment and latch function, and only then discuss an appropriate moving-joint weatherstrip. NPS says repair and maintenance of historic windows precede replacement decisions and recognizes weatherstripping as one element of rehabilitation. [NPS9, PDF pp. 2, 6; NPS_EVAL, Standard 6] If the question is whether cold glass itself causes discomfort, the separately owned NW0230 is the correct canonical guide. If water is collecting at the sill, see NW0228. This page owns the meeting-rail versus glazing-putty evidence distinction.
Send this evidence, not a product guess
Give a preservation carpenter labelled photos A and B, a short weather/rain chronology, whether the rail latch works normally, and any suspected glazing looseness. Ask: Which joint is actually defective? Is moisture reaching the joinery? Must putty or hardware be stabilized before any new strip is considered? Will access disturb old coatings or significant original glass? Ask for an inspection method consistent with the site's conservation and safety requirements.
Unknowns: Without onsite checks, the guide cannot certify the exact leak path, the age of the putty, seal compatibility, or water-tightness. A weatherstrip part number based on a cold feeling is not defensible.
Evidence and source limits
- NPS9: US National Park Service, Preservation Brief 9: The Repair of Historic Wooden Windows (1981); PDF pp. 2, 6-7 (physical evaluation, fig. 2; Weatherization). https://www.nps.gov/orgs/1739/upload/preservation-brief-09-wood-windows.pdf
- NPS_EVAL: US National Park Service, Evaluating Historic Windows for Repair or Replacement (web current as accessed 2026-10-12); Standard 6 and repair-first discussion. https://www.nps.gov/subjects/taxincentives/windows-evaluating.htm