Slimline Aluminium Windows: Reynaers SL 38 & SL 68
Slimline aluminium windows put the emphasis on glass, not frame. Inspired Glazing designs, makes to measure and installs Reynaers SL 38 and SL 68 slimline windows for homes across Windsor, Maidenhead, Ascot and the wider Thames Valley, and we also cover West London. Our fitters are directly employed and our directors are often on site.
Call 01753 965 005 for a slimline window quote, or email Sales@inspiredglazing.co.uk to book a free design survey.
What “slimline” actually means
A sightline is the visible width of frame between the glass and the wall. The narrower it is, the more daylight you get and the more contemporary the result. Slimline aluminium systems achieve sightlines a traditional casement window cannot, while keeping modern thermal performance and multi-point security.
Reynaers SL 38 — the steel-look option
The SL 38 (SlimLine 38) gives the look of old steel windows — narrow frames, crisp lines, optional Georgian bars — with a polyamide thermal break so it meets modern energy standards. It suits period and conservation-area properties, and pairs well with steel-look internal screens.
Reynaers SL 68 — the versatile modern option
The SL 68 has a slightly deeper frame for larger sashes and higher thermal performance, making it the everyday choice for extensions, renovations and new build. It takes double or triple glazing and a wide range of opening styles.
SL 38 vs SL 68 — which to choose
| Reynaers SL 38 | Reynaers SL 68 | |
|---|---|---|
| Look | Steel-look, narrowest sightlines | Slim and contemporary |
| Best for | Period homes, conservation areas, steel-look replacements | Extensions, renovations, larger openings, new build |
| Glazing | Double | Double or triple |
| Thermal performance | Meets Part L for replacement windows | Higher — suits low-energy projects |
We fit both and will advise at survey based on your home and the look you want.
Key benefits of slimline aluminium
- Maximum glass, minimum frame
- Polyamide thermal breaks — no cold bridging
- Multi-point locking and security glazing beads
- Any RAL colour, including anthracite grey and matte black
- Long lifespan with minimal maintenance
Part L and building regulations
Replacement windows must meet Building Regulations Part L (a U-value of 1.4 W/m2K or better), plus Part F for ventilation and Part K for safety glass in critical locations. Both SL 38 and SL 68 meet this comfortably; SL 68 with triple glazing can reach around 0.8 W/m2K for low-energy projects. We register every installation for building regulations and provide the compliance certificate on completion.
Slimline bifold and sliding doors
The same slimline approach applies to doors. For folding doors that stack right back, see our aluminium bifold and sliding doors page; for a fixed “wall of glass”, Reynaers aluminium sliding doors reach very narrow central interlocks. Both are made to measure and fitted by our own team.
Why Inspired Glazing
We manufacture in our own workshop, fit with directly-employed teams (no subcontracted labour), and keep the work tidy in occupied homes. Aluminium carries a 10-year guarantee on the profile, 5 years on sealed units and 2 years on hardware.
Related pages: aluminium windows and doors in Berkshire, Reynaers windows and sliding doors, and aluminium windows in Ascot and Sunningdale.
Frequently asked questions
Are slimline aluminium windows worth the extra cost over uPVC?
For large openings, slim sightlines, a contemporary or steel-look, or to match existing frames — yes. For standard-sized openings where value is the priority, uPVC is the sensible choice. We fit both and will be honest about which suits your project.
Can I get slimline windows in a conservation area?
Often yes — the Reynaers SL 38 is regularly accepted as a steel-look replacement. It depends on the local authority and any Article 4 direction; we advise at survey.
What is the U-value of a slimline aluminium window?
A standard double-glazed SL 38 or SL 68 window meets the Part L threshold of 1.4 W/m2K; SL 68 with triple glazing can reach around 0.8 W/m2K.
How much do slimline aluminium windows cost?
As a guide, from around £950 per window supplied and fitted, with most full-house aluminium projects between £11,000 and £20,000. Every quote is fixed after a free survey. See our window cost guide for a full breakdown.
Book a slimline window survey
Call 01753 965 005 or email Sales@inspiredglazing.co.uk to book a free design survey across Windsor, Maidenhead, Ascot and the Thames Valley.