Slimline Aluminium Engineering at the Highest Standards

The Reynaers SlimLine 38 achieves what few aluminium systems can – genuinely slim profiles without sacrificing thermal insulation or weather resistance. Suitable for new-builds and as a high-quality replacement for steel windows, the SL38 delivers a sleek look that suits the demands of modern architecture while performing to the highest standards expected of contemporary Reynaers aluminium windows. Triple glazing is available alongside double glazing, with a choice of four glass types to suit a variety of project requirements.

Reynaers Ultra Slim SL38 window

Ultra slim 67mm minimum visible frame-vent width

Triple glazing option with U-values from 1.1 W/m²K

Acoustic performance up to Rw 44 dB

Secured by Design – highest levels of security

Reynaers SL38 Technical Specifications

Full technical information for the Reynaers SlimLine 38 aluminium window system, including dimensional, performance, and finishing data.

Product guidance
Double glazing1.4 W/m²K (Uw value depending on the frame/ vent combination and glass unit specification).
Triple glazing1.1 W/m²K (Uw value depending on the frame/ vent combination and glass unit specification).
Inward and outward opening casement windows.Glazing method
Drained and ventilated glazing with EPDM synthetic rubber gaskets.Choose from a full range of polyester powder coat colours and anodised finishes.
FinishingChoose from a full range of polyester powder coat colours and anodised finishes.
Dual colourDual colour available offering a different colour inside and out.
Profile assemblyWeather stripped profiles with polyamide thermal breaks.
BRE RatingCorresponds to the BRE Global Green Guide online generic specification for windows and achieves a summary rating of A, Element Number 1231500007.
SecurityMeets the very stringent requirements to be awarded the Secured By Design accreditation.
Air permeabilityUp to 600 Pa (class 4).
Wind load resistanceUp to 1600 Pa (class C4).
Water tightnessUp to 600Pa (class 9A).
Acoustic performanceRw (C;Ctr) = 37 (-1;-4) dB/ 44 (-2;-5) dB, depending on the glazing type.
Product guidance – as standard
Min. Visible width frame-vent67mm
Min. Visible width frame-vent80mm
Min. Visible width T-profile48mm
Max. height vent2200mm
Max. width vent1600mm
Max. weight vent (element)170 kg
Overall system depth frame99mm
Overall system depth vent86mm
Rebate height13.5mm
Min. Glass thickness vent16mm
Max. Glass thickness vent55mm

Reynaers SL38 Product Downloads

Download technical datasheets, system brochures, and specification documents for the Reynaers SlimLine 38 aluminium window system.

reynaers sl38 window frame

Downloads

PDF 2 files
Reynaers Ultra Slim SL38 Window Reynaers Aluminium SlimLine 38 Windows Leaflet
CAD 1 file
Reynaers Ultra Slim SL38 Window

Slim Profiles Designed for Modern Architecture

The Reynaers SL38 offers a choice of three external profiles, allowing architects to tailor the aesthetic character of the window to suit the architecture of the building. With a minimum visible frame-vent width of just 67mm, the SL38 allows large glass panels and unobstructed views with a genuinely minimalistic design quality that suits contemporary homes and commercial projects alike.

The system is equally well suited as a replacement for existing steel windows, offering a significant improvement in thermal insulation and weather resistance while preserving the slim, considered sightlines that steel-framed buildings demand. The sleek look of Reynaers aluminium makes it a natural choice for design-led projects across the UK.

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Reynaers Ultra Slim SL38 aluminium door
Reynaers Ultra Slim SL38 double glazing window

Thermal Break Technology and Weather Resistance Built In

Every Reynaers SL38 aluminium window incorporates polyamide thermal breaks as standard, significantly reducing heat transfer through the frame and supporting the energy efficiency performance of the whole building. With triple glazing achieving U-values from 1.1 W/m²K, the SL38 is a strong specification choice for low-energy new-builds and high-performance refurbishments.

Weather resistance is tested to Class 9A for water tightness and Class C4 for wind load resistance – making it a reliable and high-performing system across all weather conditions. Acoustic performance reaches up to Rw 44 dB depending on glazing type, offering homeowners and commercial project teams meaningful sound reduction in noise-sensitive locations.

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Sleek Profiles for Modern Architecture

Ultra slim SL 38 windows are crafted for contemporary buildings where clean lines and minimal framing are key. Despite their refined appearance, they deliver impressive insulation, weather resistance, and sound reduction. With a variety of opening styles and finishes available, they offer both design flexibility and high performance.

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Reynaers Ultra Slim SL38 aluminium door

Frequently Asked Questions

Key technical and specification questions answered for architects, specifiers, and homeowners considering the Reynaers SlimLine 38 aluminium windows.

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Our Projects

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Stirling, Scotland

Find out more about Stirling, Scotland

Hamill House, Scotland

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Edinburgh, Scotland

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Dollar, Scotland

Whether incorporated into a modern contemporary new build or unlocking a period property, our curtain wall can reinvigorate a property by letting the natural daylight come flooding in.

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A complete service

from design to installation.

What our customers say

Quote

Zyle supplied Passive House windows for our new build, and the system met all project expectations. Airtightness and overall performance were delivered as specified, and their technical coordination on site was reliable and detail focused.

Private Owner

Mark Reynolds, Bristol

Quote

Our vacuum glazed sash windows provide an excellent balance between heritage sensitivity and modern performance. The slim glazing preserves the character of the property while significantly improving overall comfort. Installation was precise and professionally managed.

Private owner

Laura Mitchell, Southampton

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The Passive House windows performed exactly as required within our project specification. Installation detailing, sealing, and overall execution were handled correctly, ensuring a high standard of delivery. A technically competent and reliable supplier.

Private Owner

Andrew Collins, Cambridge

Quote

We selected aluminum windows for their contemporary aesthetic and low maintenance. The proportions are well considered, and the finish quality is consistent throughout. Installation was efficient and carried out with strong attention to detail.

Private Owner

Rachel Adams, Reading

Quote

The triple glazed sash windows integrate seamlessly into the existing façade while offering a clear upgrade in comfort. Craftsmanship is evident in both joinery and installation, and the improvement in acoustic insulation is immediately noticeable.

Private Owner

Thomas Green, Nottingham

Quote

The Alu-Clad windows and doors introduced a strong architectural presence while maintaining a refined internal finish. Detailing, material quality, and consistency across the project are of a high standard. The process was structured and dependable from start to finish.

Private Owner

Olivia Bennett, Oxford

Talk to Our Team

Whether you are an architect specifying for a new project, a self-builder planning your custom home, or a developer working to a programme, our team is here to help. Get in touch for technical advice, product information, or to request a quote.

  • 124 City Road
  • London
  • United Kingdom
  • EC1V 2NX

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