I live in a self-build house completed in 2008/2009. At the time we invested in good-quality windows, though they are only double-glazed.
My understanding is that the insulating performance relies on the inert gas sealed between the panes. Over time this gas can escape, and that appears to be what has happened in our case, as the panes are consistently cold to the touch, particularly in winter. I have spoken with several window companies, all of whom recommend replacing the glass units while retaining the existing frames, which are still in excellent condition.
Before committing to that expense, I would like to know whether it is possible to refill or regas double-glazed units, or whether replacement is the only realistic option. Also, would the difference in cost be significant?
I can understand your hesitation before committing to a sizeable outlay, particularly where you invested in good-quality windows when the house was built, and the frames are still in excellent condition. With a self-build completed in 2008/2009, the windows are now about 18 years old, so it is sensible to assess them carefully rather than assume either that they have failed completely or that full replacement is unavoidable.
RM Block
The first point is that glass feeling cold to the touch in winter does not, of itself, prove that the inert gas has escaped. Double-glazed units will always feel colder than an insulated wall, especially in severe weather. The more typical signs of a failed sealed unit are condensation or misting between the panes, staining, visible seal breakdown, draughts, or deterioration around the glazing beads and gaskets. If there is no misting between the panes, the units may simply be older technology rather than defective.
The age of the windows is relevant, but not conclusive. A well-made sealed double-glazed unit can last many years, often into the 20- to 30-year range, depending on manufacture, exposure, installation and maintenance. However, standards and expectations have moved on considerably since 2008/09. Windows regarded as good quality then may now compare poorly with modern low-E, argon-filled, warm-edge units.
As regards regassing, it is technically possible in some circumstances to drill, dry, refill and reseal an insulated glass unit, but I would not regard it as the normal domestic solution. The industry is generally based around factory-made sealed units, not routine on-site gas top-ups. If gas has escaped, the underlying issue is usually the edge seal. Simply putting argon back in does not necessarily provide a durable repair unless that seal can also be reliably restored. It may sound like the cheapest answer, but in practice, it can be a stopgap repair with uncertain longevity.
Replacing the glass units only, while retaining the existing frames, is often the most balanced option where the frames are genuinely sound. It allows you to improve the glazing performance without the cost, disruption and making-good associated with removing entire windows. New sealed units could be specified with low-E glass, argon fill and warm-edge spacer bars. For a house with many windows, the savings compared with full replacement can be significant. The limitation is that this will not correct poor frame insulation, air leakage, defective gaskets or weak frame-to-wall junctions.
Full window replacement becomes more persuasive where the frames are warped, draughty, poorly insulated, difficult to operate, or if the original installation has airtightness or water-ingress issues. It is the most expensive route, but gives the greatest reset regarding performance, warranty and airtightness. It is also worth checking whether any SEAI support is available and whether your home meets the relevant eligibility criteria.
My advice would be not to assume the solution is simply to “put the gas back in”. Ask a competent glazing contractor to confirm whether there is actual sealed-unit failure, then obtain quotations for replacement glass units only and compare them with at least one full-window quotation. If the frames are as good as you describe, glass-only replacement is likely to be the best-value route.
Damian King is a chartered building surveyor and a member of the Society of Chartered Surveyors Ireland
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