Slimline Aluminium Windows — London & the Home Counties
Overview
For architectural clarity and expansive glass, nothing rivals aluminium. Thermally broken with polyamide, powder-coated to any RAL colour, and engineered to hold panes larger than any uPVC alternative — without compromising strength, longevity or thermal performance.
Thermally-broken aluminium profile (Smart Systems / AluK) · 34mm polyamide thermal break · Qualicoat Class 2 polyester powder coat · Argon-filled double or triple glazing · Concealed friction hinges
55mm Slim Sightlines
Frame profiles as narrow as 55mm on the interlock allow up to 30% more visible glass than uPVC — flooding rooms with natural light and framing views cleanly.
Thermally Broken, 0.9–1.4 W/m²K
A 34mm polyamide thermal break paired with warm-edge glazing delivers energy-efficient whole-window performance across London and the Home Counties.
Any RAL, Dual-Colour
Any RAL powder-coat finish, single or dual colour (different inside and out) — matched to your architect's specification. Anodised finishes on request.
Large Aperture Capable
Fixed panes up to 2.7m tall and structural corner posts with no visible mullion — for kitchens, garden rooms and rear extensions where the glass is the design.
PAS 24 & Secured by Design
Multi-point locking, laminated inner glass, concealed hinges and lift-off resistant hardware. Independently tested to PAS 24:2016.
20-Year Finish Warranty
Qualicoat Class 2 powder coat lasts a lifetime in UK conditions. A rigid aluminium frame will outlast the property it's installed in.
uPVC vs Aluminium vs Flush Casement
Compare whole-window U-values, energy ratings and frame performance for uPVC, aluminium and flush casement windows installed across London and the Home Counties.
uPVC
- Best for
- Every home — modern & period
- Frame sightlines
- Standard (~70mm)
- Maximum pane size
- Up to ~1.8m tall
- U-value (as low as)
- 0.9 – 1.4 W/m²K
- A+ energy rating
- Yes
- PAS 24 security
- Yes
- Colour choice
- 20+ foil finishes
- Dual inside / outside colour
- No
- Conservation-area friendly
- Case-by-case
- Mechanical (not welded) joints
- No
- Maintenance
- Wipe-clean, none
- Guarantee
- 10-year insurance-backed
Aluminium
- Best for
- Contemporary builds, large apertures
- Frame sightlines
- Slim (~55mm)
- Maximum pane size
- Up to ~3m tall
- U-value (as low as)
- 0.9 – 1.4 W/m²K
- A+ energy rating
- Yes
- PAS 24 security
- Yes
- Colour choice
- Any RAL, dual colour
- Dual inside / outside colour
- Yes
- Conservation-area friendly
- No
- Mechanical (not welded) joints
- Yes
- Maintenance
- Wipe-clean, none
- Guarantee
- 20-year finish + structural
Flush Casement
- Best for
- Period, cottage & listed homes
- Frame sightlines
- Slim, timber-look
- Maximum pane size
- Up to ~1.8m tall
- U-value (as low as)
- 0.9 – 1.4 W/m²K
- A+ energy rating
- Yes
- PAS 24 security
- Yes
- Colour choice
- Heritage foil palette
- Dual inside / outside colour
- No
- Conservation-area friendly
- Yes
- Mechanical (not welded) joints
- Yes
- Maintenance
- Wipe-clean, none
- Guarantee
- 10-year colour-fastness
Not sure which range fits your property? Book a free survey and we'll bring samples of all three to your door — no obligation, just honest advice.
uPVC vs aluminium vs flush casement — the answers we're asked most.
- Which energy-efficient windows are best for London and Home Counties homes?
- Our uPVC, aluminium and flush casement ranges achieve a whole-window U-value of 0.9 – 1.4 W/m²K. uPVC has naturally low frame conductivity, thermally broken aluminium combines slim sightlines with the same approved range, and heritage flush casements suit period and conservation homes across London and the target counties.
- When should I choose aluminium windows over uPVC?
- uPVC is a strong all-round choice for standard-sized apertures. Aluminium comes into its own on large panes above roughly 1.8m, contemporary builds where slim sightlines matter, and projects needing a bespoke RAL or dual inside/outside colour. For modest openings focused on thermal performance, uPVC is usually the natural fit.
- Will flush casement windows suit a conservation area or listed building?
- Yes — flush casements are our go-to for conservation areas, AONBs and listed properties. The sash sits flush with the frame (mimicking traditional timber joinery), corners are mechanically jointed rather than welded, and heritage foil finishes replicate painted timber convincingly. We regularly get them approved where standard uPVC would be refused.
- Can I mix window types on the same house?
- Absolutely — and we often recommend it. A common combination is flush casements to the front elevation for kerb appeal and standard uPVC or aluminium to the rear where a contemporary look and larger glazed openings take priority. Colours can be matched across ranges so the house reads consistently from every angle.
- How long do each type of window last?
- Modern uPVC frames are engineered for 35+ years of service and come with a 10-year insurance-backed guarantee. Aluminium frames outlast the building in most cases and carry a 20-year finish guarantee. Flush casements share uPVC's core structure with heritage foils that carry a 10-year colour-fastness warranty. All three use the same locking systems and Q-Lon seals.
- Which range offers the widest colour choice?
- Aluminium is the clear winner — any RAL colour, matt or satin, plus different colours inside and out. uPVC comes in 20+ foil finishes including anthracite grey, Chartwell green, cream and popular woodgrains. Flush casements share the heritage end of the uPVC palette (painted-timber creams, sage, off-black) and are limited to a single colour throughout.
- Are all three ranges equally secure?
- Yes — every window we install is PAS 24 tested and fitted with multi-point locking, laminated glass options and Secured by Design compatible hardware. The frame material doesn't change the security rating; the locking system, glass specification and installation quality do.
- How do I choose between the three ranges for my home?
- Start with the property's character. Period cottage or listed home in a conservation area → flush casement. Contemporary new-build or large glazed opening where sightlines matter → aluminium. Everything else, where value and long-term thermal performance are the priority → uPVC. Book a survey and we'll bring samples of all three so you can compare them at the house.
The homeowner's guide to uPVC vs Aluminium vs Flush Casement.
An 8-page PDF you can read in ten minutes. Side-by-side specs, clear performance comparisons, range-by-range detail and the six questions we're asked most. No email required — download and share freely.
- Full specification table — U-values, sightlines, guarantees, design suitability
- Which range suits period, contemporary and conservation-area homes
- Six FAQs and a checklist for booking your survey
Instant download · No email required · Share it with your architect, builder or partner.
Engineered to the millimetre.
Every frame we install is made to your survey sizes with the following performance envelope as standard.
- U-value (whole window)
- 0.9 – 1.4 W/m²K
- Sightline (interlock)
- 55 – 65 mm
- Max fixed pane
- 2.7 m tall · up to 3.5 m² per panel
- Acoustic reduction
- Up to 42 dB Rw with laminate + acoustic interlayer
- Security
- PAS 24:2016 · Secured by Design · Doc Q compliant
- Finish
- Any RAL Qualicoat Class 2 polyester powder coat · dual-colour available
- System
- Smart Alitherm 300 / AluK 58BW & similar
- Guarantee
- 10-year installation · 20-year powder coat
The aluminium windows family.
Every one of the following styles is available in the aluminium windows range — mix, match and specify at survey.
A calm, predictable process.
No sales calls, no pressure, no surprises. Every project follows the same six steps — with a named surveyor from start to finish.
- 01Day 0
Enquire
Send drawings or photos — we advise on system choice, including thermal, structural and heritage considerations, within one working day.
- 02Week 1
Design consultation
For extension and larger projects, our surveyor works directly with your architect or main contractor on sightlines and structural openings.
- 03Week 2–3
Survey & sign-off
Post-brickwork survey to millimetre tolerance, hardware and colour samples delivered, fixed quotation confirmed.
- 04Weeks 3–11
Manufacture
Powder-coated in the UK and assembled to your survey sizes. Typical lead time 5–8 weeks for aluminium systems.
- 05Fit week
Installation
Two- or three-person CERTASS-registered fit team with lifting equipment for large panes. Cleaned, sealed and certified before we leave.
- 06Ongoing
Aftercare
CERTASS certificate lodged, insurance-backed guarantee registered, annual courtesy inspection available on request.
When aluminium windows isn't the right answer.
We'd rather lose a job than sell the wrong window. Here's when to consider the alternatives.
Aluminium Windows across London
and the Home Counties.
We install aluminium windows across six counties — every project surveyed, made and fitted by our in-house team. Choose your county to read local knowledge, planning notes and recent work.
See all areas coveredAluminium Windows — installed.
A selection of recent installations across London and the Home Counties, photographed on site.
Practical answers.
Everything homeowners ask us about aluminium windows — survey, lead times, guarantees and coverage.
When are aluminium windows the right choice?+
For contemporary properties, larger apertures and rear extensions, aluminium offers slimmer frames, more glass and a lifespan measured in decades. On smaller period cottages, uPVC or flush casements usually suit better; we advise honestly at survey.
What colours are available?+
Any RAL. The most popular finishes are RAL 7016 (Anthracite Grey), RAL 9005 (Jet Black), RAL 7021 (Black Grey), RAL 9001 (Cream) and Bronze textures. Dual-colour (different inside/out) is available across the range.
Do aluminium windows get cold or condensate?+
Modern aluminium uses a 34mm polyamide thermal break inside the frame which stops cold transfer. With warm-edge spacer bars and A-rated glazing, condensation and cold-frame feel are eliminated — performance rivals uPVC.
What U-value do thermally broken aluminium windows achieve?+
Our aluminium windows achieve whole-window U-values of 0.9–1.4 W/m²K. The exact result depends on the frame, glass, spacer and opening size confirmed during your London or Home Counties survey.
What affects an aluminium window specification?+
Aperture size, structural requirements, frame system, colour and glass all shape the final specification. A measured survey confirms the right system for each opening.
Can you match my architect's specification?+
Yes — we work with Smart Systems, AluK, Reynaers and Schüco and can quote against a named system, sightline or U-value if specified. We supply CAD sections and NBS specs on request.
What's the biggest pane you can fit?+
A single fixed lite up to 2.7m tall and 3.5m² per panel with standard glass. Larger sizes are possible with structural glass and specialist lifting on site.
How long is the lead time?+
5–8 weeks from signed order for standard RAL colours, longer for anodised or bespoke textured finishes. Book your survey early if you're aligning with builder programme dates.
Are they Building Regs compliant?+
All installations meet Approved Documents L (energy), F (ventilation — trickle vents fitted as standard since 2022), Q (security) and B (fire egress). CERTASS compliance certificate is lodged after every installation.
Do you install into new-build openings?+
Yes. We work with main contractors and self-builders across London and the Home Counties, either survey-and-fit or supply-only. Structural opening tolerances and sequence of trades are agreed in writing.
Enquire about
Aluminium Windows.
Speak with our design team, book a home survey, and receive a fixed written quotation — all with no obligation.
Call · 020 3633 0405