If you have a room in your home that never quite warms up — the spare bedroom that's always chilly, the dining room you avoid in winter, or the living room where everyone gravitates towards the radiator — the cause is almost certainly your windows or doors. Understanding why this happens is the key to choosing the right fix, and avoiding expensive solutions that don't address the real problem.
How Double Glazing Keeps You Warm (And What Happens When It Fails)
A modern double-glazed window works by trapping a layer of inert gas — usually argon — between two panes of glass. Argon conducts heat far less efficiently than air, creating an insulating barrier that keeps warmth inside and cold outside. The sealed unit is bonded with a spacer bar and sealed with specialist compounds to keep the gas in and moisture out.
Over time — typically 15 to 25 years — those seals degrade. Once they fail, the argon gas gradually leaks out and is replaced by ordinary air, which conducts heat 34% more efficiently. Moisture also enters the gap, which is why you see misting or condensation between the panes. A failed sealed unit can lose up to 70% of its original insulating performance, turning your double glazing into little more than two sheets of glass with a damp gap between them.
Bristol's Housing Stock and Cold Room Problems
Bristol's diverse housing stock creates specific cold room challenges. The Victorian and Edwardian terraces across Clifton, Redland, Bishopston, and Bedminster often feature large bay windows and tall sash windows — beautiful architecturally, but presenting substantial glass area for heat to escape through. Many were fitted with their first double glazing in the 1980s and 1990s, meaning those sealed units are now 30-40 years old and well past their effective lifespan.
The 1960s to 1980s housing found across Fishponds, Kingswood, Henleaze, and Bradley Stoke typically received budget double glazing that was state-of-the-art at the time but is now significantly outperformed by modern units. These properties often have the most dramatic cold room problems because the glazing has failed without obvious visible signs — there may be no misting, but the gas has still escaped.
Properties in exposed coastal positions along Portishead and Clevedon face accelerated seal degradation from salt air and wind-driven rain, often developing cold room issues several years earlier than identical properties inland.
The Diagnostic Approach: Finding Where Heat Is Escaping
Not all cold rooms have the same cause, and the right solution depends on an accurate diagnosis. When we assess a cold room, we check every potential heat loss point: sealed unit integrity (has the gas escaped?), seal and gasket condition (is air leaking around the frame?), frame integrity (is there warping, gaps, or deterioration?), and glass specification (is it low-E coated or plain float glass?). We also consider the room's orientation — north-facing rooms with large windows lose heat fastest — and the number and size of glazed openings.
Solutions: From Targeted Repairs to Full Upgrades
The good news is that cold room problems are entirely fixable, and often at a fraction of the cost of full window replacement. If the sealed units have failed, we can replace just the glass units within your existing frames — typically £75-£200 per window — restoring full thermal performance without the disruption and expense of new frames. If draughts are contributing, gasket replacement and seal renewal address that. For period properties where the original frames must be preserved, secondary glazing offers excellent insulation at £100-£300 per window.
For properties with very old or poor-quality frames, a full window upgrade to A-rated double glazing with low-emissivity coatings, argon gas filling, and warm-edge spacer bars delivers the maximum improvement. Modern A-rated windows are approximately three times more thermally efficient than the double glazing fitted in the 1990s. We always recommend the most cost-effective solution for your situation — repair where it makes sense, upgrade where the long-term savings justify the investment.