The fog is insidea sealed cavity

A failed edge seal on the insulated glass unit. Two lites of glass are bonded around a spacer with a butyl vapour barrier and a structural silicone seal, and the cavity between them is sealed at the factory. When that assembly opens up, insulating gas leaves and humid outside air comes in. Every time the glass drops below the dew point of that trapped air, moisture condenses on the cavity faces — surfaces ② and ③ — where nothing you can hold will ever reach it.

No. The fog is inside a sealed assembly. Cleaning surface ① and surface ④ has no effect on the two surfaces facing the cavity, because you cannot get to them without breaking the unit apart. Replacing the sealed unit is the only outcome that restores both clarity and insulating performance.

Drilling a port, flushing the cavity and fitting a breather vent will often clear the visible haze. What it does not do is restore the unit: the cavity is now vented to outside air, the gas fill is gone permanently, and the desiccant is spent. Any mineral etching already on surface ③ stays there. We do not offer it, because the unit still has to be replaced later and nothing about the thermal performance comes back.

No, and in most cases it should not be. We replace only the sealed glass unit inside the existing sash or frame. Frame, hardware, trim, weatherstrip, exterior finish and the wall opening are all left alone. Full window replacement is the right call when the frame itself is rotted, racked, or the sash no longer holds square — and we will tell you when that is what we are looking at.

Survey and measure is one visit. Custom units are typically fabricated in three to five business days. Installation runs roughly thirty to sixty minutes per opening, so most houses are finished in a single installation day. From first call to clear glass is usually seven to ten business days.

That is the whole job. We match overall thickness, lite thickness, tint, spacer type and colour, coating position and gas fill, plus grille profile and layout where there is one. Get the coating on the wrong surface and the replacement reads differently in daylight and behaves differently in winter, which is exactly the mistake we are measuring to avoid.

The moisture inside the cavity is contained, but the conditions that produced it often are not. A unit with no gas fill runs cold enough to condense room air on surface ④, and that water runs down onto the sill and the frame. Wood sills swell, paint lifts, and the glazing pocket stays wet. Where the fogging came from a leaking joint or blocked weeps in the first place, that frame problem is still live until it is corrected.

Three things do most of the work: warm-edge spacer and dual-seal construction in the unit itself, a glazing pocket that drains — clear weeps, setting blocks at the quarter points, correct edge clearance — and perimeter sealant that is maintained rather than left split. We correct the pocket while the sash is open, which is the part a straight glass swap usually skips.

Only the failed ones, in most houses. Units that are still sealed are doing their job and there is no performance reason to disturb them. Where a run of windows went in at the same time and several are already showing early haze, doing them together means one measure, one fabrication run and one install day. We give you the condition of every opening and let you decide the order.

We work across Washington DC, Northern Virginia and the Maryland suburbs — the full list of communities is on our service area page. If you are unsure, call (703) 470-7867 and we will tell you straight away.