I thought buying round windows would be simple.
I just wanted something that looked right, fit the space, and held up to the weather. But once I started reaching out to suppliers, things got frustrating fast.
Some didn’t reply. Others sent quotes that made no sense. A few even told me to buy square windows and “just frame them round later.” That’s when I realized most suppliers didn’t really get what I needed.
So I took matters into my own hands. I asked around, compared products, and spoke with people who’d gone through it before. Slowly, I figured out which companies were actually helpful and which ones wasted time.
In this guide, I’ll share 8 round window suppliers that stood out. Some I’ve worked with myself. Others came highly recommended by people I trust.
If you’re feeling stuck or unsure where to start, this should point you in the right direction.
Let’s get into it!
Quick Comparison Chart
Before we get into the details, here’s a quick side-by-side look at all 8 round window suppliers. This gives you a clear snapshot of who’s who before diving deeper into each one.
| Manufacturer | Head Office | Specialty | Strengths | Best For | Limitation / Not Ideal For |
| Internorm International | Austria | Energy-efficient round windows | Passive-rated systems, sleek Euro designs, strong performance | Passive homes, premium residential builds | Higher pricing; must go through authorized dealers |
| J. Sussman, Inc. | USA (New York) | Historic + architectural custom work | Deep experience in curved aluminum, expert restoration focus | Churches, restorations, curved aluminum projects | No standard models; long lead times for custom work |
| Vallisco | China (Shanghai) | Full-home door and window systems | Handles round and arch windows, full villa packages, export-ready | Villas, hotels, multi-window projects | Doesn’t serve single-window or one-off buyers |
| Radial Windows | UK (Telford) | Curved and circular aluminum windows | Smooth integration with modern wall designs, UK-based support | Modern builds, curved-wall applications | Not ideal for standard or high-volume window types |
| Neuffer Windows + Doors | Germany (Stuttgart) | Heritage style + modern performance | Mixes tradition and insulation tech well, strong export base | Custom homes, energy-focused builds | International shipping; longer lead times |
| Precision Millworks | USA | Wood-clad radius and arched windows | Great for restorations, offers solid build in small batches | Traditional homes, boutique renovations | Less suited for single window orders or bulk retail |
| Marvin Windows & Doors | USA (Minnesota) | Wide range of round-top options | U.S. brand variety, good for mix-and-match shapes | Residential projects with mixed shapes | Better for full projects than piecemeal orders |
| Classic Windows, Inc. | USA (Illinois) | Durable radius and geometric windows | Strong construction, practical for tough site conditions | Builders needing sturdy custom shapes | Not for high-design, luxury detailing |
Now that you’ve got the big picture, let’s look at each manufacturer more closely in the sections below.
1. Internorm International GmbH
Internorm began as a small workshop in Austria in 1931. Today, it’s one of Europe’s most recognized names in windows and doors. Though the company has grown, it remains family-run, with a strong focus on product consistency and service.
What sets them apart is their full in-house production. They don’t rely on third-party components, which helps reduce issues and gives them more control over quality.
Product Range
- uPVC Windows: Durable vinyl frames with multi-chamber insulation and modern styling. Suitable for residential projects where energy savings and easy upkeep matter.
- uPVC/Aluminum Hybrid Frames: Combines the thermal benefits of vinyl with the strength and finish of aluminum. Ideal for harsher climates or modern homes needing sleek profiles.
- Timber/Aluminum Windows: Real wood inside with weather-protected aluminum outside. Offers a warm look indoors while handling outdoor exposure well.
- Round, Curved, and Arch-Shaped Windows: Customizable radius windows made in-house with strong sealing and multiple glazing options. A solid choice for villas, B&Bs, or design-driven spaces.
- Entrance Doors, Sliding Doors, Lift-Slide Systems: Large-format openings that match the window systems. Options include low thresholds, security features, and thermal break frames.
- Built-In Blinds and Insect Screens: Integrated systems that fit seamlessly into the frame. Helps keep the design clean and cuts down on external add-ons.
Manufacturing Capabilities
Internorm controls every step of production from raw materials to final assembly. All round and specialty shapes are made in their own facilities, not subcontracted. That includes triple-sealing for insulation and full compatibility with Passive House standards.
They produce over 1 million units annually and are known for precise craftsmanship. I’ve personally seen their windows installed fit was snug, seals were firm, and the finish was clean.
Reputation & Certifications
- CE Certified: Meets European Union safety and performance standards. Products are tested for wind resistance, water tightness, and mechanical durability.
- ISO 9001 Certified: Follows international quality control systems across all factories. Helps maintain consistency from batch to batch.
- Passive House Institute Partner: Supports ultra-low energy building designs. Their window systems meet the airtightness and insulation targets needed for these builds.
- Award-Winning Designs: Recognized across Europe for innovation in security, energy performance, and aesthetics. Several product lines have received international design awards.
Final Verdict
Internorm is a strong option if you want reliable round windows backed by in-house manufacturing and solid technical performance. However, their prices sit at the higher end, and you’ll need to go through an authorized dealer for quotes and support. If quality and long-term comfort are your priority, they’re worth considering.
2. J. Sussman, Inc.
J. Sussman, Inc. has been around since 1906 and is still run by the same family. Based in New York, they’ve built a name by taking on custom aluminum window projects that most suppliers won’t touch.
They specialize in rounded, curved, and arched designs perfect for older homes, churches, or projects with special shapes. If you need a custom fit that blends with the original look, this team knows how to deliver.
Product Range
- Round and Arch-Top Aluminum Windows: Built from scratch for each order. Often used in renovations, high-end homes, and specialty builds.
- Curved and Bent Aluminum Frames: Precision-formed to match existing designs or create new ones. Helps achieve shapes most standard systems can’t handle.
- Skylight Systems: Custom aluminum skylights for flat or pitched roofs. Available in fixed or venting styles.
- Sunrooms: Framing systems designed for glass enclosures or additions. Fully custom based on layout and climate needs.
- Storm Windows and Ventilators: Adds energy protection and airflow to older or non-standard openings. Fits both commercial and residential projects.
- Glass and Metal Bending Services: Standalone service for bending aluminum and glass to spec. Handy for restoration or one-off architectural elements.
Manufacturing Capabilities
Every project is handled at their New York workshop, nothing outsourced. They work directly from specs, sketches, or architect drawings and use in-house bending machines to shape glass and metal with precision.
They don’t offer standard sizes or models. Each window starts as a custom build, giving you full flexibility over shape, size, and detail.
Reputation & Certifications
- Historic Restoration Partner: Trusted on projects like St. Patrick’s Cathedral and the Hoover Dam Visitors Center. Known for matching complex originals without shortcuts.
- Architectural Glass Association Member: Active in professional glass and metalworking groups. Keeps them up to date with technical and industrial practices.
- Respected for Craftsmanship: Repeat business from architects, contractors, and preservation groups. Many clients come through referrals or past experience.
Final Verdict
J. Sussman, Inc. is a go-to for custom round and arched windows, especially if you’re dealing with historical details or non-standard shapes. They work closely with your design and handle every piece in-house. Just keep in mind that highly custom work may take longer than standard builds.
3. Vallisco
Vallisco was officially launched in 2019, but its roots run deeper backed by over 20 years of experience through its parent company, Qeeka Home. They operate out of Shanghai and focus on supplying full project builds, not just individual windows or doors.
Their team works best with house owners, builders, and hotel renovators who need everything to line up frame by frame, door by door. If you’re managing a property from start to finish, they’re built for that kind of order.
Product Range
- Aluminum and Wood Windows: Includes casement, sliding, fixed, tilt-turn, and round shapes. Options are available in modern or traditional architectural styles.
- Full Door Systems: Offers main doors, French doors, sliding systems, and bi-fold doors. All options can be customized for color, frame depth, and handle type.
- Curtain Walls and Glass Partitions: Used for larger openings, modern facades, or room dividers. These systems are built with structural strength and thermal performance in mind.
- Sunrooms and Glass Houses: Designed for outdoor living spaces or custom additions. Frames are reinforced and weather-sealed for durability in all seasons.
- Custom Window Shapes and Finishes: Round, arched, and non-standard shapes are supported. Frame finishes include powder-coated, anodized, and wood grain looks.
Manufacturing Capabilities
Vallisco runs its own production facility, giving them better control over timelines and precision. They accept private label and OEM work, and their machinery supports cutting, sealing, and assembling all in-house.
Every product is made to order. Whether it’s color, glass type, or hardware, they adapt to your project—not the other way around.
Reputation & Certifications
- Backed by Qeeka Home: A well-established parent company that’s been supplying doors and windows since 2000. Vallisco benefits from their resources and factory experience.
- Project-Oriented Supplier: Most of their orders come from full builds villas, hotels, or large home renovations. They’re not a retail-style seller.
- Active Across Southeast Asia and Europe: Known for shipping project-based orders overseas. They’re familiar with international expectations and planning needs.
- Modern Online Presence: Website and documentation show polished builds, organized delivery, and satisfied clients across different regions.
Final Verdict
Vallisco is built for property owners and project teams who need a reliable partner for round windows and more. Their experience shows in how they handle full-home setups, and their in-house production means fewer headaches during planning. Just keep in mind they’re not the best choice if you’re only buying one or two pieces.
4. Radial Windows
Radial Windows has been building custom aluminum windows in the UK since 1985. Their team specializes in circular, arched, and curved shapes, exactly the kind of windows that many manufacturers avoid.
I first came across them during a heritage renovation that called for non-standard frames. Radial didn’t just offer the right shapes they delivered clean finishes and clear technical details that made the whole process easier.
Product Range
- Round and Circular Windows: Built with thermally broken aluminum frames and available in fixed or opening types. Ideal for modern homes or traditional buildings that call for symmetry and style.
- Arched and Curved-On-Plan Windows: Designed to follow curved walls or add soft lines to flat surfaces. Each one is made to match your exact radius and dimensions.
- Radius-Cornered and Curved-Head Designs: Combines straight frames with subtle curves. Often used in transitional architecture or facades needing visual flow.
- Custom-Shaped Aluminum Louvres: Functional vent panels shaped to match curved walls or circular openings. Adds airflow without sacrificing design.
- Over 150 RAL Color Finishes: A wide selection of powder-coated options. Lets you match frames to other architectural elements easily.
Manufacturing Capabilities
Radial handles everything in-house from design to build, which helps them keep their shapes consistent and their quality tight. Their welded and flush-dressed joints create a clean, seamless look on every frame.
All systems are made with thermally broken aluminum, giving you strength and insulation in one. They also offer internal beading for added security without disrupting the profile.
Reputation & Certifications
- Built to BS EN ISO 9001:2015: All products meet recognized quality standards for manufacturing. Every unit goes through consistent checks before delivery.
- Featured in Notable Projects: Supplied windows for The Standard Hotel in London and other landmark builds. Proves their capability in high-spec environments.
- Preferred by Architects and Builders: Known for clear drawings, helpful support, and the ability to match complex shapes. Many clients come back for repeat orders.
Final Verdict
Radial Windows is a smart choice if your build needs round, curved, or non-standard aluminum windows. They don’t just offer these shapes they focus on them. While they’re not ideal for standard boxy projects, they’re a great match for designs that call for clean curves and technical precision.
5. Neuffer Windows + Doors
Neuffer has been making windows and doors in Germany since 1872. With over 150 years behind them, they’ve built a reputation for combining traditional looks with modern performance.
I worked with them on a heritage home where round windows had to match the original charm but still work like new. Neuffer handled both. The windows looked period-correct but opened smoothly, sealed tight, and felt sturdy.
Product Range
- Round and Arched Windows: Available in fixed, tilt-only, and pivot formats. Offered in wood, uPVC, or aluminum, with a variety of finishes and trims.
- Tilt and Turn Windows: Dual-action frames that tilt for airflow or swing open for access. Known for energy efficiency and ease of use.
- Sliding and Folding Doors: Designed for wide openings with smooth operation. Great for modern builds or indoor-outdoor transitions.
- Entrance Doors: Made-to-order entry systems with thermal insulation and security options. Materials include wood-aluminum or uPVC composites.
- Passive House-Certified Windows: Engineered for high insulation value. Suitable for ultra-low energy homes and cold climate builds.
Manufacturing Capabilities
Neuffer handles every window in-house from CAD drawings to final assembly. They work with a range of materials and can create fully custom shapes and sizes based on your project needs.
Their production includes triple glazing, advanced weather seals, and energy-rated components. Each window is made to meet European performance and safety standards.
Reputation & Certifications
- 150+ Years of Experience: One of the oldest names in European window manufacturing. Known for their consistency and long-term reliability.
- Certified for Energy and Safety: Products meet EU standards for insulation, structural strength, and fire resistance.
- Trusted for Custom Projects: Frequently used on restorations, high-end homes, and international builds needing custom specs.
- Blend of Traditional and Modern: Offers heritage-style designs with today’s thermal and acoustic performance.
Final Verdict
Neuffer is a great choice if your project needs round windows with both timeless design and high energy performance. Their experience shows in the fit, feel, and finish of each frame. Just note because every unit is custom-built and ships from Germany, you’ll need to factor in longer lead times and international freight. But if quality and style both matter, Neuffer delivers.
6. Precision Millworks
Precision Millworks has been crafting custom wood and wood‑clad windows and doors for decades under Enviroguard. Based in the U.S., they serve residential and boutique hospitality projects with careful attention to detail.
I discovered them through a renovation project that needed radius and round windows across several openings. Their team worked from hand drawings and mounted pieces seamlessly, matching period style with precision.
Product Range
- Radius & Round Wood-Clad Windows: Solid wood interiors with durable aluminum-clad exteriors. Offers fixed or opening units in custom diameters and arch profiles.
- Custom Arched and Curved Windows: Both true arch and segmental curved designs. Ideal for villas, character homes, and architectural highlights.
- Entrance Doors & Door Systems: Matching wood-clad doors including French, sliding, and pivot styles. Options include sidelights, transoms, and radial door frames.
- Matching Architectural Millwork: Includes radius moldings, jambs, and panels to complete cohesive window-door suites. Custom stained finishes and pre‑finished options available.
- Thermally Efficient Glazing Options: Triple or double-glazed units with low-E coatings. Designed for energy performance in cold or temperate climates.
Manufacturing Capabilities
Precision Millworks does everything on-site from design to final trim. Their radius window line is engineered specifically for spherical and arched openings. Team members can translate sketches or architect plans into full-size templates before production.
All frames are built to order using high-grade hardwoods, weather-resistant coatings, and industry-standard energy glazing. Quality control is part of every step, from rough cuts to factory-finished delivery.
Reputation & Certifications
- Trusted By Architects and Designers: Frequently recommended on restoration and boutique projects. Known for matching style and fit when standard windows won’t do.
- Enviroguard Brand Experience: Backed by a parent brand with over two decades of performance in wood-clad systems and radius solutions.
- High Customer Satisfaction: Positive client reviews highlight the responsiveness and clarity of their project support and site templates.
- Energy-Efficient Ratings Available: Products meet U.S. and Canadian energy standards, with options for high-performance glazing and thermal seals.
Final Verdict
Precision Millworks offers excellent solutions for anyone needing round or arched wood-clad windows built with accuracy and energy efficiency in mind. Their custom approach makes them less suited for single-window replacements but if you’re working on multi-window designs or boutique homes, they deliver consistent quality and visual harmony.
7. Marvin Windows & Doors
Marvin doesn’t just make windows they build them to suit how people live. Based in Minnesota and family-owned for generations, they focus on thoughtful design and dependable performance across a wide range of home styles.
What makes Marvin stand out is how well their products fit into both traditional and modern spaces. Whether it’s a farmhouse remodel or a coastal new build, they offer curved and specialty shapes that feel intentional not forced.
Product Range
- Essential Round Top Windows: Crafted in fiberglass (Ultrex®), available in quarter-round, half-round, and ellipticals. Low-maintenance, fade-resistant, and built to last.
- Elevate Round Top Windows: Wood interiors with aluminum-clad exteriors and coastal-certified performance (IZ3). Ideal for elegant homes near the sea.
- Signature & Ultimate Round Top Windows: Available in over 60 shapes like Gothic, oval, polygon, and eyebrow. Works alone or paired over casements or picture windows.
- Pivot and Rotary Specialty Shapes: Includes full-circle pivot windows and 360°-rotating sash options. Great for attics, gables, or unique architectural spaces.
- Supporting Systems & Accessories: Includes matching frames, divided-lite options, glazing packages (dual, triple, tempered, laminated), and color/hardware customization.
Manufacturing Capabilities
Marvin handles design and assembly in-house, offering both standard and custom shapes with detailed CAD and construction support. They maintain tight quality control across materials wood, fiberglass, aluminum-clad.
Each round-top window is built to exact size, with options ranging from direct-glaze fixed models to operable systems. Marvin delivers templates and drawings to streamline installation.
Reputation & Certifications
- Extensive Historical Use: Marvin windows appear in high-end residential and restoration projects where round shapes and precise detailing matter.
- Broad Shape Selection: Over 1,000 sizes and custom options, including full, half, and quarter rounds, ovals, gothic types, and more.
- Certified Finish and Durability: Their Ultrex® fiberglass finish meets AAMA 624 standards and is resistant to fading, cracking, or peeling.
- Design Flexibility: Offers coordinating divided lites, grille patterns, hardware, glazing upgrades, and more to suit architectural detail and climate needs.
Final Verdict
Marvin is a solid pick if you’re after round-top windows that blend beautiful form with reliable performance. From standard styles to custom arcs and pivot shapes, they cover almost every need. While they may be more suited to comprehensive window-wall systems rather than small batch orders, they’re a strong option for design-focused homeowners, architects, and boutique builds.
8. Classic Windows, Inc.
Classic Windows is based in Libertyville, Illinois, and has been building wood-clad window systems since the 1990s. Their work leans heavily on durable clean joints, thick aluminum cladding, and solid sash construction.
They’re not flashy, but they’re dependable. If you want windows that are built right and built once, Classic fits the bill, especially for projects that require radius or geometric shapes.
Product Range
- Radius & Round-Top Windows: Custom-built with pine interiors and extruded aluminum exteriors. Made in full circles, half-rounds, ovals, or segmental arches.
- Geometric Fixed Windows: Includes triangles, trapezoids, and custom polygons. Used as architectural accents or above/alongside operable units.
- Casement, Awning & Picture Windows: Open-out designs with energy-efficient glazing. Built with their proprietary “Seal Smart” system for weather resistance.
- Double-Hung Windows: Traditional operation with tilt-in cleaning. Features reinforced frames and Cardinal Glass for performance.
- Doors and Specialty Mullions: Matching doors and curved mullions made to coordinate with arched window layouts.
Manufacturing Capabilities
Classic controls everything under one roof. They fabricate their own cladding, cut their own curves, and manage glass installation without outside vendors. Each unit is sized and shaped to spec—no reliance on standard templates.
What they deliver is simple: heavy-duty window systems that don’t need babysitting after install.
Reputation & Certifications
- Direct-Supply Model: Ships directly from their Illinois factory to builders with no dealer markup or distributor delays.
- Durable Build Materials: Uses extruded (not roll-formed) aluminum and solid pine for frame stability and long-term finish quality.
- Jobsite-Focused Support: Offers shop drawings, templates, and builder-specific documentation to streamline installs.
- Specialty Shape Capabilities: Their ability to handle radius, eyebrow, and elliptical builds consistently makes them a go-to in curved frame work.
Final Verdict
Classic Windows, Inc. doesn’t overpromise they just focus on strong construction, clean fit, and accurate custom shapes. They’re a good match for builders and contractors who want a supplier that’s steady and straightforward. However, If you’re after flashy styling or mass-market product lines, this probably isn’t your match but if reliability matters, they’ll get the job done.
Conclusion
Finding the right round window supplier isn’t easy I learned that the hard way. But after sifting through confusion, I found companies that actually care about fit, finish, and service. That’s what this guide gives you.
Each supplier here brings something different. Whether you’re building a villa, remodeling a guesthouse, or managing a hotel project these are trusted names worth checking out.
So don’t stay stuck. Start the search with confidence.
Ready to move forward? Contact Vallisco today.
