For homeowners, architects, and builders who want the warmth of real wood without compromising exterior performance, Accoya is one of the strongest wood options available for exterior windows and doors, especially for coastal homes where salt-laden air, wind-driven rain, high humidity, intense UV exposure, and constant wet-dry cycles can quickly expose the weaknesses of ordinary building materials.

What Is Accoya?

Accoya begins as sustainably sourced radiata pine, then undergoes an advanced modification process called acetylation. This process permanently changes the wood at the cellular level, reducing its ability to absorb moisture.

The result is a high-performance wood with exceptional dimensional stability and resistance to decay. Unlike a surface treatment, the modification extends through the wood, helping Accoya perform consistently in demanding exterior conditions.

Exceptional Stability

One of Accoya’s greatest advantages is its dimensional stability. It is far less prone to swelling, shrinking, warping, and cracking than conventional wood.

For exterior windows and doors, this means:

• More consistent sash and door operation
• Better long-term alignment of reveals and weather seals
• Reduced stress at joints and glazing interfaces
• A cleaner appearance with fewer movement-related defects
• More reliable performance through seasonal humidity changes

This stability is especially valuable in large operable windows, French doors, patio doors, and entry doors, where even small amounts of movement can affect performance.

Resistance to Moisture, Rot, and Decay

Accoya’s acetylation process improves biological durability and moisture resistance, helping protect the wood against rot and decay.

That does not eliminate the need for quality design, drainage, factory finishing, and proper installation. But it gives the window or door a more durable wood foundation from the start.

For exposed locations near the ocean, bays, lakes, or high-humidity regions, that added resilience can make a meaningful difference in long-term ownership.

Longer-Lasting Finishes

Exterior coatings perform best when the substrate beneath them remains stable. Because Accoya moves less with changes in moisture, paint and stain systems can remain intact longer than on conventional wood.

A high-quality factory finish still requires routine inspection and maintenance, particularly in harsh coastal environments. However, a more stable wood helps reduce the cracking, joint opening, and coating breakdown that can lead to frequent refinishing.

Real Wood Without Sacrificing Performance

Accoya gives architects and homeowners the benefits of natural wood—warmth, depth, custom profiles, detailed joinery, and design flexibility—while offering performance suited to demanding climates.

It can be used for:

• Casement, awning, and fixed windows
• Tilt-and-turn windows
• Double-hung and traditional divided-light windows
• Custom shaped and historic replacement windows
• Entry doors, French doors, and glazed patio doors
• Contemporary large-format wood openings

Whether the project is a shingle-style beach house, a coastal cottage, a contemporary waterfront residence, or a hospitality property, Accoya allows real wood to remain part of the design.

A Complete Exterior Window or Door System

The wood species is only one part of performance. A coastal-grade window or door should also include high-quality glazing, durable weather seals, proper drainage, a tested exterior coating, and corrosion-resistant hardware such as stainless steel or bronze.

Accoya Windows

Accoya wood windows combine the natural beauty of real wood with exceptional stability that resists shrinkage, swelling, and rot. Engineered for outstanding performance, sustainability, and low maintenance and backed by a 50-year warranty.

Benefit from long-lasting wood windows that maximize beauty and require minimal upkeep.

High performance wood windows-Quality where it counts

From its superior insulation to its lasting good looks, Accoya wooden window frames outperform other woods and uPVC in every way. Not to mention being better for the environment and healthier for you. Whether you’re looking for traditional wooden sash windows, stylish bay windows, practical casement windows or impressive architectural glazing – Accoya delivers on all fronts.

• 50 Year warranty: Our outstanding 50-year above ground warranty is here to give you complete confidence that your Accoya wood windows will stand the test of time.
• Low maintenance: Accoya wooden window frames deliver all the beauty of natural wood with none of the downsides. That means minimal upkeep and maximum beauty.
• Highly stable: Wood windows made from Accoya are highly stable and have shown improved coating lifetime performance with many types of coatings, resulting in extended maintenance intervals.
• Highly durable: Highly durable & naturally insulating, you can lock in the warmth and lock down the price of your energy bills with Accoya wood windows. All while saving time, money and hassle on maintenance.

Accoya Doors

External wood doors protect your home from the elements, so choosing one that’s built to last is essential. Accoya wood doors combine natural beauty with exceptional durability and stability, offering a sustainable, high-performance solution that stands the test of time in any climate. Accoya wood doors are designed for lasting performance, delivering exceptional strength and resilience compared to traditional wood. They also offer excellent thermal insulation and superior stability, meaning less shrinking, swelling, and maintenance over time.

• Long lasting: Solid wood doors with long lasting performance – giving you the beauty of wood combined with peace of mind for your property.
• Dimensionally stable: Highly stable so harsh environments will not impact installation ensuring that your door’s performance stays true and coatings last longer.
• Natural wood: Accoya is real wood, but its excellent stability and durability outperforms even traditional hardwood front doors, such as oak.
• Low maintenance: With 3-4 times less swelling than traditonal wood species, Accoya’s minimal movement keeps projects looking great saving time and money in the long run.

Tested to the limit

60 year service life

After running tests and reviewing external and independent data, the BRE concluded that Accoya wood, provided best design practice is followed, has a service life expectancy of 60 years when used in exterior applications such as wooden front doors and wooden door frames.

Part Q compliancy

To enable building regulation Part Q compliancy, Accsys in collaboration with UKAS approved test houses of timber window and wooden door manufacturers, ancillary suppliers to our industry and the BWF Federation has developed a security global assessment. This document allows for the successful security testing of Accoya windows and doors to be cascaded down to window and door manufacturers, thus limiting the need for further testing.

Thermal Performance

Accoya thermal conductivity has been assessed by IFT Rossenheim, Germany in accordance with EN 12664 and then developed into the required declared value format, under the most rigorous European assessment methods by the EN ISO 10456: 2008 procedure for determination of declared and design thermal values.

In comparison to other standard wood types for joinery, Accoya thermal conductivity is:

› Superior to softwood by 8%

› Superior to hardwood by 30%



At Cypress Windows and Doors, we can combine Accoya with custom manufacturing, high-performance glass, premium hardware, and precision joinery to create windows and doors designed for long-term exterior exposure. Accoya is not simply an alternative to ordinary wood. It is a smarter foundation for a lasting wood window or door system.