Windows are one of the most important design decisions in any self-build project. They do far more than just let in light – the right windows will influence the energy efficiency of your home, how comfortable it feels year-round, and the overall look and character of the building. They are also a significant investment, often making up a large part of the build budget, so choosing wisely is essential.
For self-builders, the challenge is the sheer range of products and brands available. From high-performance, Passivhaus-certified glazing to sleek architectural rooflights and bespoke glass walls, the options can feel overwhelming. Each system comes with its own strengths, costs, and installation requirements, which can make the decision process confusing without expert guidance.
In this article, we’ll break down the choice into two key categories: window manufacturers (the companies that design and produce the systems themselves) and suppliers (UK-based specialists who advise, supply, and often install the products). By understanding both sides, you’ll be better placed to decide not just which windows you want, but also how to source and fit them successfully in your self-build project.
TOP WINDOW MANUFACTURERS IN THE UK MARKET
When it comes to windows for self-build projects, the manufacturers you choose play a crucial role in the overall performance, comfort, and aesthetic of your home. In this section, we focus on the most highly regarded window manufacturers, highlighting key criteria that self-builders should consider, including materials & construction, energy efficiency, design & aesthetics, and value for self-builders.
Internorm – Premium Passivhaus Windows
- Origin & Reputation
Founded in 1931 in Austria, Internorm is Europe’s leading Passivhaus-certified window manufacturer with a strong reputation for innovation and sustainability. - Materials & Construction
Offers uPVC, uPVC-aluminium, and timber-aluminium composites, with precision-engineered frames and alu-clad timber systems like the HF 520. Built for durability and minimal maintenance. - Energy Efficiency
Market leader in Passivhaus performance, with triple glazing achieving U-values as low as 0.62 W/(m²·K). Proprietary I-tec technology boosts insulation, airtightness, and security. - Design & Aesthetics
Highly customisable with ranges (Studio, Home Pure, Home Soft, Ambiente) catering to both modern and traditional builds. Wide colour and finish options. - Value for Self-Builders
Top-end pricing, but unmatched for ultra-low-energy or Passivhaus projects. Ideal for those prioritising sustainability, customisation, and long-term performance.
Learn more: Internorm UK
Rationel – Scandinavian Craftsmanship
- Origin & Reputation
Danish-founded, Rationel is known across Northern Europe and the UK for blending traditional joinery with modern energy performance. - Materials & Construction
Timber and alu-clad timber windows, designed for durability and low maintenance. Precision joinery makes them well-suited for timber-frame builds. - Energy Efficiency
Excellent thermal performance, with many products approaching Passivhaus standards. Suitable for low-energy builds. - Design & Aesthetics
Timeless Scandinavian look with clean lines and versatile styles. Options for both modern and traditional homes. - Value for Self-Builders
Premium pricing, similar to Internorm, but with stronger appeal for traditional or hybrid timber builds. A balance of high-quality materials and attractive design.
Learn more: Rationel UK
Velfac – Modern Minimalist Style
- Origin & Reputation
Another Danish brand, Velfac is widely recognised for contemporary design and slimline frames. - Materials & Construction
Timber and alu-clad timber windows, engineered for precision and durability. Strong emphasis on low-maintenance finishes. - Energy Efficiency
Strong thermal and airtightness performance, suitable for low-energy or near-Passivhaus projects. - Design & Aesthetics
Signature slim sightlines and minimalist style, ideal for contemporary architecture. Highly customisable glazing and colour options. - Value for Self-Builders
Premium to upper-mid pricing, more affordable than Internorm and Rationel. Best suited for modern self-builds where design sharpness is a priority.
Learn more: VELFAC UK
Velux – Market Leader in Roof Windows
- Origin & Reputation
Global leader in roof windows, founded in Denmark and renowned for reliability, innovation, and aftercare. - Materials & Construction
Timber and alu-clad frames with wide glazing options (energy-efficient, noise-reducing, solar control). - Energy Efficiency
Many models offer high thermal performance, with Passive House-certified options available. Excellent airtightness and insulation. - Design & Aesthetics
Extensive range of rooflight sizes, styles, and finishes. Trusted for both modern and traditional projects. - Value for Self-Builders
Mid-range pricing with strong aftercare and support. Ideal for most self-builders seeking dependable roof windows with proven performance.
Learn more: Velux UK
Fakro – Cost-Effective Roof Windows
- Origin & Reputation
Polish manufacturer and one of the largest roof window brands worldwide, positioned as a strong alternative to Velux. - Materials & Construction
Timber and aluminium-clad roof windows with durable glazing options. Designed for long-term reliability. - Energy Efficiency
Solid energy performance, with some models meeting Passive House or equivalent standards. - Design & Aesthetics
Range of modern roof windows and skylights, suitable for pitched roofs, lofts, and attic conversions. - Value for Self-Builders
Most affordable option among these manufacturers. Delivers reliable daylighting solutions at competitive prices, making it a cost-effective alternative to Velux.
Learn more: Fakro UK
Dako – Innovative European Windows
- Origin & Reputation
Dako is a Polish manufacturer with a growing presence in the UK market, known for high-quality timber, aluminium, and aluminium-clad timber windows suitable for energy-efficient self-builds. - Materials & Construction
Offers durable, low-maintenance timber and alu-clad timber frames, including tilt-and-turn and casement systems. Frames are precision-engineered for smooth operation and long lifespan. - Energy Efficiency
Products meet rigorous European energy standards, with options suitable for low-energy and near-Passivhaus homes. Triple-glazed units provide excellent thermal performance and sound insulation. - Design & Aesthetics
Modern, minimalist aesthetics with clean lines and slim sightlines. Wide choice of finishes and colours allows integration into both contemporary and traditional projects. - Value for Self-Builders
Competitive pricing relative to premium European brands, offering strong performance and design at a more accessible cost. Ideal for self-builders seeking a balance between energy efficiency, style, and affordability.
TOP WINDOW SUPPLIERS IN THE UK
When it comes to buying and installing windows, self-builders usually interact with suppliers rather than manufacturers. Suppliers not only provide the products but also offer expert advice, coordinate delivery, and often handle installation. Choosing the right supplier can make a significant difference in the overall quality, timeline, and satisfaction of your project.
Most leading suppliers provide comprehensive warranties covering both product and installation, so the main differences lie in design specialism, service, and pricing. The following overview introduces each supplier, highlighting their strengths, service approach, and typical pricing level to help you find the best match for your self-build.
- The main UK suppliers differ by specialism:
- Bespoke architectural glazing (Glass Worx)
- Slimline sliding doors (Maxlight)
- Panoramic sliding doors (Ultraline)
- Minimal-frame glazing (Clear Living)
Glass Worx
- Origin & Reputation
UK-based supplier specialising in bespoke glazing solutions, from architectural glass walls to large-scale features for high-end residential projects. - Service & Support
Strong design expertise, helping self-builders integrate complex, custom glazing into their projects while balancing aesthetics and structure. - Delivery & Reliability
Handles complex installs with precision and safety; lead times depend on project complexity. - Ideal For
Self-builders seeking one-off, high-impact glazing that makes a statement. - Pricing: Premium/high – generally more expensive than Ultraline or Maxlight due to bespoke, one-off nature.
Learn more: Glass Worx
Maxlight
- Origin & Reputation
Leading UK supplier of slimline sliding doors and expansive glazing, widely used in contemporary homes for seamless indoor–outdoor connections. - Service & Support
Advises on system selection, integration into structure, and detailing for large openings. - Delivery & Reliability
Experienced installation teams ensure smooth operation and precise alignment, even for oversized sliding units. Moderate lead times for standard systems. - Ideal For
Self-builders wanting sleek, modern sliding doors and wide glazed openings to bring in light and views. - Pricing
Slightly lower than fully bespoke suppliers like Glass Worx but comparable to Ultraline.
Learn more: Maxlight
Ultraline
- Origin & Reputation
Specialist in panoramic sliding door systems, frequently used in extensions and open-plan builds to maximise daylight and garden views. - Service & Support
Supports design integration, ensuring large sliding doors work seamlessly with modern layouts. - Delivery & Reliability
Professional installation teams guarantee airtight performance and smooth operation; lead times can be extended for custom sizes. - Ideal For
Self-builders aiming for wall-to-wall glass doors that create light-filled, open-plan living spaces. - Pricing:
Upper-mid to premium – comparable to Maxlight, usually more affordable than Glass Worx’s bespoke solutions.
Learn more: Ultraline
Clear Living
- Origin & Reputation
UK supplier of minimal-frame glazing systems for architectural projects, ideal for self-builders pursuing bold, design-led homes. - Service & Support
Offers detailed planning and design advice to achieve ultra-clean sightlines and maximum light penetration. - Delivery & Reliability
Precise installation, with strong emphasis on weatherproofing, thermal performance, and detailing. - Ideal For
Self-builders prioritising contemporary aesthetics and unobstructed glass façades. - Pricing
Premium – on par with Maxlight and Ultraline, reflecting the specialised systems and installation expertise.
Learn more: Clear Living
HOW TO CHOOSE: MANUFACTURER VS SUPPLIER
When selecting windows for your self-build, it’s important to understand the difference between manufacturers and suppliers – and why you often need both.
Manufacturers determine the product quality, performance, and certifications. They create the window systems, from timber and aluminium frames to high-performance glazing.
Suppliers, on the other hand, provide guidance, installation, and aftercare. Many UK-based suppliers have established relationships with manufacturers, which can mean access to the latest products, potential deals, and expert advice on what works best for your build. Crucially, suppliers with experience in self-build projects understand the unique challenges of planning approvals, site conditions, and coordination with builders or architects. This knowledge ensures smoother installations, fewer delays, and windows that perform as intended.
For a smooth self-build experience, choose the right combination: a manufacturer whose product meets your performance and design requirements, paired with a supplier who has experience, established manufacturer links, and a proven track record in installation and project support.
Choosing the right windows is a key investment for any self-build project, impacting comfort, energy efficiency, and long-term resale value. By understanding the differences between manufacturers and suppliers, and selecting options that balance performance, aesthetics, and support, you can make informed decisions that benefit your home for years to come.
For independent guidance tailored to your self-build, the team at ACA can help you evaluate window choices, consider materials and systems, and recommend suppliers and manufacturers best suited to your project.
For further reading, explore our resources on Passivhaus design, energy efficiency, and other self-build considerations to ensure your project achieves both style and performance.
