Why Some Rooms Stay Cold
In most UK homes built before 2010, the double glazing uses basic clear glass with air fill. These units have a U-value of approximately 2.8 W/m²K — three times worse than modern specifications. The glass surface gets cold, radiates cold into the room, and creates convection currents that make the room feel draughty even when all the windows are closed.
Rooms with multiple windows, large glass areas, or north/east-facing orientation are worst affected. Conservatories and extensions built with basic glass are notoriously cold in winter and expensive to heat.
The Specification Upgrade
Replacing the sealed units with Low-E coated glass + argon gas fill transforms cold rooms:
U-value reduction: From ~2.8 to ~1.1 W/m²K (61% reduction in heat loss through glass).
Inner surface temperature: 5-8°C warmer — stays above the dew point in normal conditions.
Cold radiation: Virtually eliminated — the Low-E coating reflects radiant heat back into the room.
Convection draughts: Stopped — warmer glass surface prevents cold air downdraught.
When to Recommend Triple Glazing
For rooms that need maximum comfort — bedrooms, living rooms with large glass areas, or conservatories — triple glazing delivers U-values from 0.6 W/m²K. The inner pane surface stays within 1-2°C of room temperature. There is essentially zero cold radiation and zero convection draught. It's a premium specification, but for cold rooms it can be transformative.
Cost vs Benefit
Sealed unit replacement costs a fraction of full window replacement. Your customer keeps their existing frames, handles, and hardware. The glass upgrade alone delivers the thermal improvement. For a typical 3-bed house with 10-12 windows, the glass upgrade pays for itself in 3-5 years through reduced heating costs — and the comfort improvement is immediate.