Flagship guide · 9 min read
The Ultimate Guide to Aluminium Windows
Everything worth knowing before specifying aluminium windows, from frame construction and thermal performance to colour, glass and realistic pricing.
← Architectural Aluminium
Aluminium Windows
Slim-profile aluminium glazing specified around the architecture, not the price list. Steel-look and heritage sightlines for period and planning-sensitive properties; clean contemporary frames for extensions and new build.
5.0 from 7 Google reviewsWhat are aluminium windows best suited to?
Aluminium windows suit openings where the frame should be as slim as possible and the glass as large as possible. Because aluminium is strong for its weight, sightlines can be narrow while panes stay big, which works well on contemporary extensions, new build, and steel-look or heritage replacements where slender bars matter. They also take a durable powder-coated finish that needs no repainting. Thermal performance depends on the system, glass make-up and configuration, so the whole-window figure is confirmed against the specification rather than assumed from the material.
From a real Windows in the Lakes project
Near Kirkby Stephen, Cumbria · 20 windows · 5 doors
Full House Aluminium Windows, Kirkby Stephen
All windows had to be fitted directly into original stonework and traditional stone cills, with uneven surfaces throughout and both original and newly built openings to reconcile. Conservation-appropriate detailing was required without additional aluminium cills.
Face-drained systems were specified so the frames could sit directly within the stone surrounds and retain the original cills. Our survey team coordinated closely with the supplier on delivery, and installers worked to fine tolerances — even the perimeter mastic seal was applied by hand to follow the irregular stone.
Read the project storyRecent installations
Aluminium Windows we have designed, surveyed and installed
See it in a real home
Whole-House Aluminium Glazing, Contemporary Clad Remodel
A drone film of a full-house aluminium glazing package — slimline sliding doors, square picture windows and black frames throughout, over a timber-clad remodel and pool terrace.
See it in a real home
A House Rebuilt Around Its Glazing
A drone film over a whole-house remodel near Penrith — rising across the brick and render frontage, over the tiled hip and rooflight, then settling on the full-width glazed garden elevation.
See it in a real home
A Garden Room Glazed on Three Sides
A drone film over a brick garden room near Keswick — dropping from the rooftops onto the tiled gable and its rooflights, then working around two bifold runs folded open onto the terrace.
See it in a real home
A Brick Barn Range, Opened to the Courtyard
A drone film over a converted brick barn range near Cartmel — opening high above the courtyard and fields, then tracking slowly along the elevation past two aluminium French door sets, arched-head timber-look uPVC windows and planted stone terraces.
See it in a real home
A Whole House, Front to Garden
A drone film over a remodelled family house near Windermere — descending onto the render-and-brick front elevation and its bay windows, then rising over the ridge to the glazed garden room and lantern behind.
See it in a real home
Courtyard Garden Room, Brick Barn-Style New Build
A tracking film along a brick courtyard range in South Lakeland — paired aluminium French doors, full-height fixed screens between brick piers and a bifolding return onto sandstone paving.
Why this system exists
01
Sightlines measured in millimetres
Narrow frames and larger panes mean more glass, more daylight and a quieter elevation — the frame recedes and the view does the work.
02
Specified for exposure
Cumbrian weather is unforgiving. Systems, gaskets and drainage are selected for the orientation and exposure of each elevation.
03
Planning-aware detailing
Steel-look and Crittall-style profiles suit conservation areas and listed settings where slender bars and traditional proportions matter.
04
Finished to last
Marine-grade polyester powder coatings, dual-colour options and bronze, anthracite or heritage tones that hold their finish for decades.
Suitability
Where aluminium windows belong, and where they do not
Best suited to
- Large openings and long spans where a slim frame keeps the elevation calm
- Contemporary extensions, garden rooms and new-build elevations
- Steel-look and heritage replacements needing slender bars and true proportions
- Exposed elevations where a durable factory finish matters more than repaintability
- Dual-colour schemes, where inside and outside need different finishes
Less suitable when
- Listed buildings where the consenting authority expects timber joinery
- Budgets where a like-for-like uPVC replacement would meet the brief
- Elevations where a deep, sculpted painted-timber profile is the design intent
- Very small punched openings, where slim sightlines add little visible benefit
Where aluminium is the right answer
Aluminium is the specification of choice where openings are large, sightlines must be slim and structural spans are demanding. Its strength-to-weight ratio allows frames a fraction of the width of alternative materials while carrying significantly larger panes of glass.
On renovation work we frequently use aluminium to introduce a modern, disciplined elevation to the rear of a traditional Lakeland property, while retaining heritage detailing at the front.
Assessment before specification
Every project begins with an assessment of the openings, structure and exposure before we recommend a system. Once an order is placed, a full measured survey confirms every dimension before manufacture. There is no single best aluminium window; there is a correct one for your opening, exposure and architectural intent.
Considered detailing is what separates a fitted window from a finished one.
Recent installs
Recently completed across Cumbria and the North West
Real installations from across Cumbria and the North West — surveyed, specified and installed under our own supervision.
Alunet Aluminium Picture Windows, Eco Forest Lodges
Ravenstonedale · 2026
Alunet Aluminium French Door Sets, Eco Forest Lodges
Ravenstonedale · 2026
Glazed Rear Elevation, Heritage Aluminium Windows
Near Penrith · 2025
24 Heritage Aluminium Windows, Matt Black
Near Penrith · 2025
Garden Room Glazed on Three Sides, Jet Black Bifolds
Near Keswick · 2025
Four-Panel Aluminium Bifold Run
Near Keswick · 2025
Aluminium French Door Sets In Original Brick Arches
Near Cartmel · 2025
Timber-Look uPVC Windows, Barn Conversion
Near Cartmel · 2025
Steel-Look Georgian-Bar Casements & Bay Windows
Near Windermere · 2025
Full-Width Garden Room Glazing & Lantern Rooflight
Near Windermere · 2025
Full-Width Slimline Sliding Doors, Clad Remodel
North West · 2025
Black Aluminium Picture Windows, Timber-Clad Elevation
North West · 2025
32 Heritage Windows and 4 Doors, Stone Self Build
West Yorkshire · 2025
Black Heritage Windows with Georgian Bars
West Yorkshire · 2025
Triangular Gable Glazing and Heritage Casements
West Yorkshire · 2025
Steel-Look Doors and Screens, Barn Conversion
North West · July 2026
Flush Casement Windows, Oak-Framed Garden Room
Cumbria · July 2026
Grey Aluminium Windows and Doors, Full Elevation
North West · July 2026
Steel-Look French Doors and Window Set
North West · June 2026
Anthracite Bifolding Doors, Brick Extension
North West · July 2026
Steel-Look Screen and Doors
North West · July 2026
Three-Panel Slimline Sliding Doors
North West · July 2026
Five-Panel Bifolding Doors, Cottage Extension
Cumbria · June 2026
Steel-Look Doors and Matching Screen
North West · June 2026
Slimline Sliding Doors, Brick Courtyard
North West · June 2026
Full-Width Steel-Look Glazed Screen
North West · June 2026
Heritage French Doors with Side Screens
North West · May 2026
Aluminium Windows and Glazed Doors
North West · May 2026
Bifolding Doors to a Barn Courtyard
Cumbria · May 2026
Gable-End Glazing and French Doors
North West · May 2026
Internal Steel-Look Screen
Cumbria · April 2026
Bifolding Doors, Clad Garden Room
Cumbria · April 2026
Aluminium Vertical Sliding Sash Windows
Cumbria · March 2026
Slim 20mm Sliding Door Set
Windermere · May 2026
Heritage French Door Set
Barrow · May 2026
Single Door and Window
Windermere · May 2026
AB60 Smart French Doors
Bowness · May 2026
Heritage Alunet Bifold Doors
Lancaster · May 2026
AS20 Smart Slimline Sliding Doors
Carlisle · January 2026
Farmhouse Extension Aluminium Windows
Carlisle · January 2026
Full House Aluminium Windows
Kirkby Stephen · August 2025
Technical
Specification at a glance
Figures shown are indicative system capabilities. Final performance depends on the chosen system, dimensions, glass make-up, configuration and installation detail, and is confirmed on the manufacturer data sheets issued with every quotation. Guarantee cover varies by product and component. The applicable frame, glazing, hardware and installation guarantees are set out in writing at quotation stage.
- Frame material
- Thermally broken aluminium
- Typical U-value
- From 1.2 W/m²K (whole window)
- Glazing
- Double or triple, argon filled, low-e soft coat
- Finish
- PPC RAL, dual colour, textured and heritage tones
- Security
- PAS 24 compliant options, multipoint locking
- Guarantees
- Confirmed by product and component with quotation
Specify it your way
Colours, glass, hardware and details worth saving
Save anything that appeals and it travels with you — into your Inspiration Collection and then into your consultation.
Frame colours
- RAL 7016 AnthraciteThe contemporary default — quiet against stone and render alike.
- Jet BlackSteel-look elevations and rural conversions.
- Painted CreamTraditional joinery language for cottages and farmhouses.
- Pure White InteriorDual-colour frames that disappear from inside the room.
Glass & glazing
- Slim 20mm sliding sightlinesMaximum glass, minimum frame, panes that stack behind one another.
- Steel-look divided lightsAstragal bars and fine profiles echoing original metal windows.
- Flush casementsSashes sitting level with the frame, as painted joinery would.
Hardware
- Flush lever handlesMinimal, colour-matched and unobtrusive on modern frames.
- Concealed hingesNothing interrupting the sightline when the frame is closed.
- Monkey-tail handlesForged period detailing for heritage and conservation openings.
Design features
Sightlines measured in millimetres
Narrow frames and larger panes mean more glass, more daylight and a quieter elevation — the frame recedes and the view does the work.
Specified for exposure
Cumbrian weather is unforgiving. Systems, gaskets and drainage are selected for the orientation and exposure of each elevation.
Planning-aware detailing
Steel-look and Crittall-style profiles suit conservation areas and listed settings where slender bars and traditional proportions matter.
Finished to last
Marine-grade polyester powder coatings, dual-colour options and bronze, anthracite or heritage tones that hold their finish for decades.
How it is fitted — filmed on site
Fitting a Gable-End Apex Screen
Two installers set, pack and level a raked aluminium gable screen on a first-floor deck, then glaze the apex — filmed over a working morning.
0:32 · Windermere, Cumbria · August 2025
This is the part of a project homeowners rarely get to watch: a raked, gable-end aluminium screen being set into a finished opening at first-floor level. The frame is offered up dry, packed off the structure, checked for plumb and level, and only then fixed and glazed.
Everything about the sequence is deliberate. The deck is boarded and the working area kept to one side so the finished surfaces below are never used as a workbench. Packers carry the load at fixed points rather than the frame being pulled square with fixings. The apex angle is cut and jointed in the factory to the surveyed pitch, so nothing is adapted on site.
- System
- Smart aluminium, gable-end apex screen
- Stage shown
- Frame fitting through to sealing and finishing
- Access
- First-floor deck, boarded working zone
- Frames
- Powder-coated aluminium, raked to the roof pitch
- Glazing
- Double glazed units, externally glazed, internally beaded
- Filmed
- Windermere, Cumbria, August 2025
Frame fitting, packing and levellingGlazing the unitsAdjustment and alignmentWeather sealingTrims and finishing
How it is fitted — filmed on site
Commissioning a Four-Panel Sliding Door Run
The moment a glazed, fifteen-metre sliding run is first moved on its track — the commissioning and adjustment stage, filmed on a garden room build near Grasmere.
0:17 · Near Grasmere, Cumbria · September 2025
This is the stage homeowners feel every single day for the next twenty years, and the one that separates a competent fit from a genuinely good one. The frames are in, the units are glazed, and the installer is now running each panel end to end by hand — repeatedly — to prove the track, the rollers and the interlocks before anything is signed off.
What you are watching is a test, not a demonstration. A correctly commissioned sliding panel moves with one hand, at the same effort from one end of the run to the other, and stops dead where you let go of it. Any change in resistance across the track means the cill is not perfectly level or the rollers need setting, and that is corrected now — while the building is still open and everything is accessible.
- System
- Slimline aluminium sliding doors, multi-panel run
- Stage shown
- Glazing through to commissioning, adjustment and handover
- Setting
- Single-storey garden room, timber frame, open to the field
- Threshold
- Low-level track set into the deck structure
- Frames
- Powder-coated anthracite grey aluminium
- Filmed
- Near Grasmere, Cumbria, September 2025
Glazing the unitsAdjustment and alignmentTrims and finishingClean down and handover
Brochure
The Aluminium Windows guide, including the mistakes worth avoiding
Configurations, sightline comparisons, structural considerations and the questions to ask before you order. Printed copies posted on request.
Start the conversation
If you are planning an extension, renovation or new-build project and want glazing designed and installed without compromise, we would be glad to talk.
Direct
01768 254554projects@windowsinthelakes.co.ukBased in Appleby-in-Westmorland, with installation teams across Penrith, Keswick, Kendal, Windermere and the South Lakes.
Common questions
Aluminium Windows: your questions answered
Practical answers to what homeowners ask us most about this system. Anything else, just ask.
Book a Design ConsultationVisit the Knowledge CentreKnowledge Centre
Guides worth reading first
Flagship guide · 6 min read
The Best Windows for a Barn Conversion
A barn conversion is not a window replacement job. It is a small number of large, unrepeatable glazing decisions, and the material and detailing you choose will define how the finished building reads.
Flagship guide · 8 min read
Choosing Windows for a Lake District Property
Lake District houses ask more of their glazing than most. This is how we specify windows and doors for stone cottages, farmhouses, renovations, extensions and contemporary homes across Cumbria.
Get an initial project price
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Designed with
Frequently paired with this collection.
RAL 7016 Anthracite GreyColours Studio
Solar Control GlassGlass Studio
Brushed Bronze Pull BarHardware Studio
Flush ThresholdsDesign Details
Obscure Glass CollectionGlass StudioDual Colour: Anthracite / WhiteColours Studio
Design Studio
Keep exploring in the Design Studio
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Let’s design something exceptional.
Bring us your drawings, your site photographs or simply an idea. We will tell you what is possible, what it should cost and how long it will take.