IN Brief:
- AkzoNobel and the University of Amsterdam compared timber window and façade systems with aluminium, steel, and PVC alternatives.
- In the assessed scenarios, wood recorded substantially lower cradle-to-grave carbon footprints than the alternative substrates.
- The study identifies substrate selection as the main carbon lever while protective coatings can support durability and service life.
AkzoNobel has published a lifecycle study developed with the University of Amsterdam comparing timber window and façade systems with alternatives including aluminium, steel, and PVC. The assessment places substrate selection at the centre of the carbon calculation, while treating coatings primarily as a means of protecting the chosen material and maintaining its service life.
The study examines representative building elements across production, coating application, use, maintenance, transport, and end-of-life stages. In the scenarios assessed, timber recorded a lower cradle-to-grave carbon footprint than the non-wood alternatives, although the results depend on the specific products, lifecycle assumptions, and maintenance regimes used in the comparison.
For window frames, AkzoNobel reports a total footprint of approximately 19kg CO2e per square metre for the assessed wood system, compared with around 93kg CO2e per square metre for aluminium. In the façade-panel comparison, the reported totals were approximately 15kg CO2e per square metre for wood, 28kg for aluminium, and 99kg for steel.
Those figures should not be read as universal values for every timber or metal product. The lifecycle assessment uses market-average Environmental Product Declarations for the substrates and AkzoNobel Product Carbon Footprints for paints and coatings, together with assumptions covering maintenance and end-of-life treatment. Its value lies in comparing representative systems under one methodology rather than producing a fixed carbon number that can be transferred unchanged to another project.
The coating percentages underline why that distinction matters. Coatings account for approximately 21% of the assessed wood window frame’s total footprint, including maintenance applications, compared with about 4% for aluminium. Yet the overall timber system remains substantially lower because the substrate starts from a much smaller total carbon burden.
The same pattern appears in the façade comparison. Coatings represent approximately 37% of the assessed wood panel’s total footprint, compared with 13% for aluminium and 19% for steel. A higher percentage contribution from coatings therefore does not mean that the complete timber system carries a higher carbon impact; it reflects the relatively low total against which the coating contribution is being measured.
For architects, façade engineers, contractors, and manufacturers, the more useful finding is the hierarchy of decisions. Changing coating chemistry can alter part of an element’s footprint, but choosing between timber, aluminium, steel, or PVC can have a larger effect before the finish is applied. The coating specification then becomes relevant to whether that lower-carbon substrate maintains the performance and service life assumed in the lifecycle calculation.
Durability is particularly important for external timber because performance depends on more than the material selected at design stage. Moisture management, detailing, factory finishing, installation quality, exposure, inspection, and maintenance all influence whether a timber window or façade remains serviceable for decades or requires early repair or replacement.
Sarah Skinner, Marketing Director, Wood Finishes at AkzoNobel, said: “Manufacturers of timber windows, doors and façade components need coating systems that deliver consistent quality and reliable performance at industrial scale.” The company argues that coordinating timber selection, coating technology, and the finishing process can protect the substrate while maintaining production efficiency.
That industrial-finishing stage is an important connection between lifecycle modelling and construction delivery. Factory-applied coatings can be controlled for coverage, film thickness, curing, and handling more consistently than finishes applied in variable site conditions. Prefinished windows, doors, and façade elements can also arrive ready for installation, moving a larger proportion of work into controlled manufacturing environments.
AkzoNobel identifies waterborne, low-VOC, and UV LED-curable systems among the technologies available to manufacturers, but the study does not support treating one coating type as automatically appropriate for every application. Exposure, substrate preparation, factory process, production speed, maintenance expectations, and the intended service life all influence the final specification.
The broader construction argument for timber extends beyond windows and cladding. Engineered products such as cross-laminated timber and glued-laminated structural members can provide high structural performance at relatively low weight in suitable applications. Reduced structural weight can influence foundations, transport, and lifting requirements, while prefabrication can reduce the volume of fabrication and cutting undertaken on site.
Those advantages do not remove the normal design constraints around moisture, fire performance, acoustics, connections, durability, or responsible sourcing. Timber is not automatically the lower-carbon answer for every building component, and the AkzoNobel research does not attempt to model an entire building structure. Its conclusions are narrower: within the assessed window and façade scenarios, substrate selection dominates total carbon impact and timber performs favourably against the alternatives examined.
That narrower conclusion is useful as embodied-carbon assessment becomes more closely tied to procurement. A design team comparing competing façade packages needs Environmental Product Declarations, service-life assumptions, maintenance requirements, replacement cycles, transport, fabrication, and installation information rather than a generic claim that one material is sustainable.
Protective coatings then become part of maintaining the carbon case made at specification stage. If a relatively small coating contribution materially extends the service life of the underlying timber, it can help avoid repair or premature replacement. Conversely, a durable coating cannot erase a substantially larger substrate footprint where another technically suitable material performs better under the same assessment assumptions.
The study therefore supports a sequence rather than a blanket material rule: establish whether timber is technically suitable for the application, compare substrate impacts on a whole-life basis, and then specify finishing and maintenance systems capable of preserving the assumed service life. In the scenarios examined by AkzoNobel and the University of Amsterdam, the largest carbon decision was made at substrate selection rather than in the coating layer applied afterwards.
