Double & Triple Glazing

What is double glazing?

Double glazing is two panes of glass with an argon-filled gap and a low emissivity coating; triple glazing adds a third pane and a second gap. The frame matters as much as the glass: uPVC is the cheapest and needs no maintenance, aluminium gives slim frames and large panes, and timber suits period houses and conservation areas. Under Part L of the Building Regulations a replacement window must reach a U-value of 1.4 W/m²K or better, which is what an A-rated double glazed unit gives. Triple glazing takes that to around 0.8 and is noticeably quieter on a busy road.

We are an insulation company, so we will tell you something most window companies will not: windows are usually a smaller heat loss than the walls and the roof. A typical London terrace or semi loses around a third of its heat through the walls and a quarter through the roof, and 10 to 20% through the windows and doors. If the walls are solid brick and the loft is thin, those come first. Where the windows are single glazed, draughty or rotten, new glazing is still worth doing, and doing it in the same project as external wall insulation means the reveals, sills and the new wall thickness all line up instead of being cut around later.

Stay Warm surveys every opening, checks conservation area and listed status, and coordinates the window sizes and positions with any external wall insulation so the frames sit in the right plane. An accredited installer registered with FENSA or CERTASS fits the windows and doors and certifies them under the Building Regulations. You get one written quote, one project manager and the certificates at the end.