Both materials can be specified well or badly, and the quality of the individual product matters more than the material category.
Cost over time, not just at purchase
UPVC costs less to buy and needs no repainting. Timber costs more initially and needs a paint or oil cycle, but a well-made timber window can be repaired part by part indefinitely, where a failed UPVC unit is generally replaced whole.
The right comparison is total cost across thirty years including maintenance and eventual replacement, not the quote on the day.
Appearance and planning
Sightlines are the giveaway. UPVC sections are thicker, so glass area and proportion change on a period elevation. On listed buildings and in most conservation areas, timber in the original profile is what gets consent.
Where appearance matters but budget is tight, prioritising timber on the front elevation and accepting an alternative at the rear is a route many owners take.
Thermal and acoustic performance
Modern units in either material can achieve good thermal performance; the glazing unit and the installation seal do most of the work. Draught-proofing an existing timber window, or adding secondary glazing, closes much of the gap for a fraction of the cost of replacement.
For traffic noise, mass and cavity width matter more than frame material, which is why secondary glazing often outperforms a new double-glazed unit acoustically.
Common questions
How long do timber windows last?
Well-made and maintained timber windows last for generations, which is why so many original Victorian and Georgian sashes are still in service.
Will I get permission for UPVC?
On a listed building, very unlikely. In a conservation area it depends on the local authority and the elevation. Outside those designations, generally yes.
Is UPVC warmer than timber?
Not inherently. Timber is a reasonable insulator in its own right; the glazing unit, spacer and installation quality drive the overall figure.
Can existing windows be upgraded instead?
Often. Draught-proofing, repair and secondary glazing can transform comfort and noise while keeping the original joinery.