Misty Windows Bristol

Misty windows are caused by seal failure in the double-glazed unit. Every sealed unit has an edge seal bonding the two panes together. Over time — typically 15-25 years — thermal expansion and contraction causes micro-cracks in this seal. The insulating argon gas escapes, moist air enters, and once the internal desiccant (moisture absorber) is saturated, you get permanent condensation between the panes.

The sealed unit needs replacing, but the window frame almost certainly doesn't. This is the key distinction. We remove the failed glass unit from your existing frame and fit a brand new sealed unit into the same frame. Your frames, sills, and decoration stay untouched. It's not a repair of the old unit (that's not possible once the seal has failed) — it's a replacement of the glass only.

No. Once the seal has failed, the problem only gets worse over time. In the early stages you might see misting that comes and goes with temperature changes — this is because the desiccant still has some capacity. But eventually the desiccant saturates completely, and you get permanent fogging and mineral deposits. There's no DIY fix, no hack, and no product that can reseal a failed unit from the outside.

Each sealed unit takes approximately 1-2 hours to replace. For a typical Bristol home with 3-4 misty windows, we can usually complete the job in a single morning or afternoon. The process involves two visits: one to measure (15-20 minutes) and one to fit (1-2 hours per window). The new units are manufactured to your exact measurements, which takes 5-7 working days.

In the vast majority of cases, sealed unit replacement is the sensible choice. If your frames are structurally sound — no warping, cracking, or rot — there's no reason to replace them. You'll get identical glass performance at 60-70% less cost. We'll always give honest advice: if your frames genuinely need replacing, we'll tell you. But we won't upsell you a full window when a sealed unit does the job.

Yes — conservatories are one of our most common jobs. Conservatory glazing is especially prone to seal failure because of the extreme temperature swings (very hot in summer, very cold in winter), which accelerates seal degradation. We replace sealed units in conservatory roofs, side panels, and doors. Individual panels can be replaced without scaffold in most cases.

No — this makes the problem worse. Drilling holes lets in more moisture, removes any remaining insulating gas, and creates an air gap with no seal. You'd end up with worse insulation than single glazing, plus you void any warranty. The only proper fix is a factory-sealed replacement unit with fresh argon gas and new desiccant. We understand the temptation to try a quick fix, but it genuinely doesn't work.

Yes, significantly. A failed sealed unit has lost its insulating argon gas, meaning it performs barely better than single glazing. For a typical Bristol home with 4-5 misty windows, you could be losing 20-30% more heat through those windows compared to properly sealed double glazing. Replacing the units restores full thermal performance — most customers tell us they notice the difference in room temperature within days.

All our sealed unit replacements come with a 12-month comprehensive guarantee covering the unit, the seal, and the fitting. The sealed units themselves are manufactured to BS EN 1279 standards and come with the manufacturer's own warranty. We're FENSA certified and fully insured, so if anything isn't right, we'll come back and sort it at no extra cost.