Expert Double & Triple Glazing Installations for Homes & Businesses

Double and triple glazing are a smart investment for any home or business, offering better insulation, security and energy savings. Keystone Glazing has been installing energy-efficient windows across West Sussex and the Hampshire border for more than 25 years – from a single replacement window to a full house of new windows and doors.

We fit standard A-rated double glazing, high-performance 32mm units and full triple glazing, and we’ll give you honest advice on which makes sense for your home and budget.

Every installation is surveyed, made to measure and fitted by our own experienced team, then certified through CERTASS so you know it meets building regulations.

A-rated double glazing

Two panes of glass with an insulating gas-filled cavity and a warm-edge spacer. Modern A-rated double glazing is a huge step up from older windows and remains the best value for most homes.

High-performance 32mm units

Our answer to triple glazing: a thermally enhanced double unit with soft-coat low-E glass, argon gas and a deeper cavity. It rivals entry-level triple glazing and often fits existing modern frames, so you get most of the benefit without the cost and disruption. Read our answer to triple glazing.

Triple glazing

Three panes of glass and two insulating cavities give the lowest heat loss and the best noise reduction. Modern triple-glazed units can achieve U-values as low as 0.8 W/m²K. Triple glazing needs frames designed for the extra weight and depth, so it is usually fitted as part of new windows.

Three numbers tell you how well a window performs:

• U-value – how much heat escapes. The lower, the better. The centre pane figure is for the glass alone; the whole window figure (Uw) includes the frame and is the one that matters.
• g-value – how much free heat from the sun passes through the glass.
• Window Energy Rating (WER) – combines heat loss, solar gain and air leakage into a single A++ to G rating, like an appliance label.

Typical values for a uPVC window:

Units are W/m²K. Centre pane values to BS EN 673; figures are typical and vary by frame and glass supplier. Source: Glass and Glazing Federation, Triple Glazing Guidance.

If you’re comparing quotes, ask for the whole-window U-value, the number of low-E coatings and the unit thickness – not just “double” or “triple”.

There’s no single answer, which is why we look at each home before recommending anything:

Read our guide to double vs triple glazing for the full pros and cons.

Our suppliers manufacture both double and triple glazed units, and demand for triple glazing is growing across West Sussex as energy prices rise and standards tighten. We can supply triple glazing in any window or door we fit – uPVC, aluminium, timber-look or timber – in the same styles and colours as our double glazing. See our windows for styles and finishes.

Energy-efficient windows keep your home warmer in winter and cooler in summer, which can significantly lower heating costs. Toughened glass and reinforced frames make them harder to break into, and in a busy area they act as an effective noise barrier. Read more about the benefits of double glazing.

Windows

REHAU uPVC, SMART aluminium and Residence Collection flush sash windows, plus timber windows for period homes, in casement, sash, tilt and turn and bay styles. See our windows for styles, colours and glass options.

Doors

Endurance composite front and back doors, uPVC doors, French and patio doors, and aluminium bifolds. Design your composite door or bifold doors online before we visit.

Conservatories and roofs

Conservatories, Supalite warm roofs and rooflights and roof lanterns.

Homes and businesses

As well as homeowners, we work with landlords, builders and businesses. See our commercial glazing and trade glazing services.

Replacing every window and door at once gives your home a consistent look and the biggest improvement in warmth and security. We plan the work room by room so the house stays secure and weathertight each night, protect your floors and furniture, and take all the old frames and glass away for recycling. See our full house of Georgian-style windows in Bosham and read about how we handle old windows sustainably.

1. Free consultation and quote – we visit, measure every opening and give you a clear, fixed written quote with no pressure to buy.

2. Product selection – choose your materials, styles, colours, glass and hardware, with honest advice on what suits your home.

3. Made to measure – your windows and doors are manufactured to the exact size of each opening.

4. Professional installation – carried out by our own experienced fitters with minimal disruption, and with old frames and waste removed.

5. Certification and aftercare – we register the installation with CERTASS, hand over your guarantee and stay on hand for any questions. See our aftercare guide.

Want to know more about certificates? Read FENSA vs CERTASS. And if you’re comparing quotes, our guide to high-pressure sales tactics may help.

We install double and triple glazing across Chichester, Bognor Regis, Emsworth, Selsey, Felpham, Pagham, Barnham, Littlehampton, Arundel and the surrounding areas of West Sussex and the Hampshire border. See double glazing in Chichester and double glazing in Bognor Regis for local projects.