Wooden windows

B0C4145E-9A1C-4E80-9855-33EB3FC9E35C Created with sketchtool.
7BDF7E99-FF40-4125-9E4D-AD2D20F06698 Created with sketchtool.
7BDF7E99-FF40-4125-9E4D-AD2D20F06698 Created with sketchtool.


Quality where it counts

Accoya wooden window frames deliver all the beauty of natural wood with none of the downsides. That means minimal upkeep and maximum beauty.

From its superior insulation to its lasting good looks, Accoya timber 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.


Our outstanding 50-year above ground warranty is here to give you complete confidence that your Accoya wooden 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.


Accoya wooden windows have shown improved coating lifetime performance with many types of coatings, resulting in extended maintenance intervals.


Naturally insulating, you can lock in the warmth and lock down the price of your energy bills with Accoya windows. All whilst saving time, money and hassle on maintenance.

Accoya wood windows last a lifetime

Our lives all contain uncertainty and challenges that we have to manage and overcome. Fortunately, Accoya windows deliver certainty and durability, so you have one less thing to worry about.

Watch our Accoya film that shows how Accoya windows really do last a lifetime. 

Accoya window performance

Accoya high performance windows out-perform traditional hardwoods and in many cases, uPVC and aluminium.

Scroll left-right to view table

Key BenefitAccoyaSapeleOakMerantiIrokoRedwood
Coatings performance✓✓✓✓✓
Thermally insulating✓✓✓✓
Maintenance intervals✓✓✓✓✓

Table shows comparison between properties of Accoya wood and other wood species. For more information, see the Accoya Performance Testing Summary on the downloads page.

Wood window styles

Accoya wood is very versatile - ideal for many different types of windows to suit any home.

Tested to the limit

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 timber windows, wooden window frames and balconies.

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 up to 8%
› Superior to hardwood by 30%

Please see more information in our download section.

Coatings & Finishes

A fully factory coating is strongly recommended for Accoya windows. A variety of colours and finishes have been tested by leading coating manufacturers with outstanding results. Some examples can be seen below but the possibilities are endless.

Accoya replaces rotten softwood

Case Study

Accoya replaces rotten softwood

The owners of the Chagford Old Rectory decided it was time to replace their windows and french doors. Over the years they have been repaired and maintained but the original windows, now over 130 years old, were unsalvageable. The original wooden windows were so severely weathered they had rotted beyond repair.

To retain the original aesthetic of the property but far improve the durability of the windows, the homeowners chose Accoya wood as the replacement material. Opting for wood allowed for a more authentic style which could be handcrafted. Some of the windows were unusual sizes, so bespoke windows were a necessity. Accoya wood was chosen for its durability, stability and sustainability, alongside its low maintenance properties.

Care and maintenance

How to care for your Accoya windows

Revisited 10 years Later

Carradale House, London | 10 years on | Teknos coating

Revisited 13 years Later

Victoria House, Deal | 13 years on | Teknos Coating

Accoya window FAQs

  • Virtually all wood preserving treatments today work by impregnating toxic chemicals (such as arsenic, oils, ammonia or metal compounds) into the cell walls of the wood. This works to fill the voids within the wood but this doesn’t change the underlying chemistry. The toxicity of such products also have negative environmental implications during the serviceable life of the wood as well as during its disposal.

    As an alternative, Accoya alters the wood’s structure to the core, creating an inhospitable environment and helping to control unwanted organisms, such as bacteria, viruses and fungi. The main alternative non-toxic preservative treatment to Accoya’s acetylation is “thermal modification”, a process which works by breaking down the edible components of the wood. However, the process both discolours and weakens the wood, rendering it unsuitable for many uses.

    The Accoya production process does not weaken the original wood – in fact, its hardness is slightly improved and its bending strength uncompromised. Indeed, no modification process exists which offers the performance benefits and retained physical properties of Accoya.

  • From a technical performance perspective, in respect of attributes such as durability and dimensional stability, there is no need to finish Accoya wood for cladding and decking applications. However, joinery applications are more complex so it is recommended that you seek expert advice before using Accoya for uncoated windows and doors.

    Like any natural wood species, Accoya wood is susceptible to weathering in outdoor circumstances. All materials exposed to exterior conditions are degraded by a series of chemical, biological and physical processes. The surface of any wood will be blemished by a combination of UV, moulds, algae, mildew, yeasts and pollution.  Accoya is no exception and the initial light colour of uncoated Accoya may causes early moulds and blemishes to stand out more than on other wood types, prior to it weathering further to grey.

  • Wood is an amazing material with many possibilities and practical applications. One of the major drawbacks of wood though, especially softwood, is how it interacts with water. Moisture causes the wood to swell and shrink, and accelerates damage and decay.

    So, what is acetylation?

    Wood naturally contains some acetyls, but also a lot of ‘free hydroxyls’ – these are what water binds to, causing all those problems. In our reactors, our process uses acetic anhydride – essentially very strong vinegar – to boost the acetyl content of the wood, replacing those hydroxyls…meaning water is no longer an issue.

    This means we’re not adding anything to the wood that wasn’t already there – no toxic elements that could later leach out - we are really enhancing the natural qualities of the wood.

    Even the by-product of our process is part of the circular economy: acetic acid is valued in its own right, used in other products, processes or even turned back into acetic anhydride – offering a potentially ‘closed loop’ cycle for our chemistry.

    We constantly refine and improve our processes to improve quality and efficiency, and research the effects with different wood species.

    Watch our video here.

  • Accoya wood is made from radiata pine trees. These are sourced and taken to our production facilities in the Netherlands where they undergo a modification process, more specifically known as Acetylation. This process turns the radiata pine wood into the worlds most stable wood, Accoya.

    More information about the Acetylation process can be found here.

  • With regular inspection and care, you’ll enjoy a beautiful finish for decades to come.

    Please make sure you Inspect your joinery regularly. Any damage in the paint should be addressed immediately to prevent moisture ingress and water entrapment under the coating. Like most things, wooden joinery can greatly benefit from regular inspection, care and maintenance - just like an annual service on a boiler or car. We strongly recommend annual inspection, cleaning of the frames and maintenance.

    Please speak to your coatings supplier about supporting documentation such as care and full maintenance recommendations and watch the video below.

    This video is based on best practice techniques and will help you keep your windows looking their best for even longer.

Accoya is ideal for your windows

Read more in our blogs

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