One of the biggest decisions in any home project. Here is how to choose the right frames and glass, what the regulations require, and how to buy well.
Windows and doors do more than any other single element to set the light, the look, the comfort and the running costs of a home. They are also a big part of the budget. Choosing the right system matters, and so does buying it well. We source a full range directly from manufacturers across Europe, which cuts out the middlemen and gets you a better product for the money.
Frame materials
The frame sets the look, the slimness of the sightlines, the maintenance and much of the cost.
Aluminium. Slim, strong and low-maintenance, with the thinnest sightlines and the ability to span large openings. Powder-coated in any RAL colour, and ideal for contemporary homes, big picture windows and sliding doors. Systems we work with include Cortizo and Schuco, along with Reynaers, AluK, Smart Systems and Origin, and ultra-minimal sliding systems such as Sky-Frame.
Timber. Warm, characterful and often essential in conservation areas and on listed buildings, in both casement and sliding sash. Made by specialist joinery manufacturers such as Mumford & Wood, George Barnsdale, Bereco, Gowercroft and Timber Windows.
Aluminium-clad timber. Timber on the inside for warmth, aluminium on the outside for weather protection and low maintenance, usually triple glazed and very efficient. Brands include Internorm, Velfac and Rationel.
uPVC. The most affordable option, thermally very capable, though with chunkier sightlines than aluminium or timber. Good systems come from Rehau, Deceuninck and Veka.
Steel and steel-look. The classic black, slim, industrial look, in genuine steel (Crittall) or in slimline aluminium that mimics it for less. Popular for internal screens and doors as well as external glazing.
We are not tied to one supplier, so we match the system to the project, the setting and the budget.
The glass itself
The frame gets the attention, but the glass does much of the work.
- Double or triple glazing. Double glazing suits most projects; triple glazing is worth it for new builds, low-energy homes, noisy locations and the last word in comfort.
- Low-E coatings and gas fill. A low-emissivity coating reflects heat back into the room, and argon or krypton gas between the panes improves insulation.
- Warm-edge spacers. The strip around the edge of the unit; a warm-edge spacer cuts cold spots and condensation.
- Solar control glass. Reduces overheating from the sun, increasingly important for large areas of south-facing glass.
- Acoustic glass. Laminated glass that noticeably cuts noise near roads or railways.
- Safety and privacy glass. Toughened or laminated glass where the regulations require it, and obscured glass for bathrooms.
Two numbers to know: the U-value (how much heat the window lets out, lower is better) and the g-value (how much solar heat it lets in).
Design features to consider
- Sightlines: how slim the frames are, which changes the whole feel of a room.
- Big glazing: picture windows, sliding doors (lift-and-slide is smoother than bifold for large spans), corner glazing and roof lanterns.
- Thresholds: flush, level thresholds for a seamless inside-outside transition.
- Colour: single or dual colour, so the inside and outside can differ.
- Heritage detail: sash horns, astragal bars and slim double glazing to suit period and listed homes.
- Ventilation and security: discreet trickle ventilation, and multipoint locking to the required security standard.
The regulations and efficiency ratings
Windows and doors are covered by Building Regulations, and it is easy to fall foul of them. The headlines for 2026:
- Part L (energy). Replacement windows must achieve a whole-window U-value of 1.4 W/m²K or lower, or reach Window Energy Rating band B or better. New-build homes are tighter at 1.2 W/m²K, and nothing may be worse than the backstop of 1.6 W/m²K.
- Part F (ventilation). Since June 2022, background ventilation (usually trickle vents) is required on most replacement windows, so a home does not become too airtight.
- Part O (overheating). New homes must limit overheating, which affects the size, orientation and solar-control specification of large areas of glass.
- Safety and security. Toughened or laminated safety glass is required in critical locations, and new dwellings must meet a security standard (Part Q).
- Sign-off. Replacement glazing must be certified, either through a FENSA-registered installer or building control.
Window Energy Ratings run from A++ (most efficient) down to E, a simple way to compare products at a glance.
What it costs (a rough guide)
Every project is different, but as a rough guide for a supplied-and-fitted window:
| Material | Best for | Indicative cost per window |
|---|---|---|
| uPVC | Value, good efficiency | £450 to £900 |
| Aluminium | Slim, contemporary, big glazing | £900 to £1,800 |
| Timber (casement or sash) | Heritage, character, conservation areas | £1,200 to £2,500+ |
| Aluminium-clad timber | Warmth plus low maintenance, triple glazed | £1,200 to £2,600+ |
| Steel or ultra-slim aluminium | The slim black look | £2,000+ |
Large sliding doors, structural glazing and roof lanterns are priced separately and can run from several thousand pounds into the tens of thousands.
How we help
We source direct from manufacturers across Europe, including Cortizo and Schuco, alongside trusted British timber makers, which means better systems at better value than the usual retail route. We survey, advise on the right frames and glass for your home and budget, handle the supply and the fitting, and make sure everything meets the building regulations. One team, accountable for the whole thing.
Regulations and figures are indicative for 2026 and change over time. Brand names are examples of the systems we work with.