A sealed unit is the glass part of a double glazed window: two panes, a spacer bar, a desiccant and an edge seal. It can be replaced on its own, in your existing frame, whenever it fails or whenever you want better thermal performance.
Overall thickness has to match, or the beads will not close. Beyond that you have real choices: the low-E coating (soft coat performs better than hard coat), the spacer bar (a warm-edge polymer spacer beats aluminium and reduces edge-of-glass condensation), and the cavity fill (argon is standard, krypton for thin cavities).
Get all three right and a unit replacement is one of the highest-return energy improvements available on an existing house.
| Job | Typical cost |
|---|---|
| Misted / blown double glazed unit, replaced per unit | £80 – £190 |
| Same-day glass replacement, standard pane per pane | £120 – £280 |
| Toughened safety glass, replaced per pane | £150 – £350 |
Ranges include VAT and installation. Final price depends on size, spec, access and site condition — a survey gives you a fixed number.
Yes, provided the new unit is the same overall thickness. Swapping an old clear double glazed unit for a modern low-E, argon-filled, warm-edge unit typically improves that window's U-value from around 2.8 to nearer 1.4 W/m²K.
Typically 15–25 years. South-facing units generally fail first, because they take the biggest daily temperature swings.
Misted, blown and foggy double glazing repaired across the UK. We replace the failed sealed unit and keep…
Toughened and laminated safety glass supplied and fitted UK-wide. Critical locations under Part K, securi…
Same-day and next-day aluminium window and door repairs across the UK. Misted units, broken glass, handle…
What U-value your replacement windows must achieve under Part L in 2026 — 1.4 W/m²K for an existing dwell…
Free survey, fixed price, no pressure. Or call us and we'll give you a realistic ballpark in five minutes.
