Are Timber Windows Really Better for the Environment?
Many window manufacturers claim to produce environmentally friendly products. At Gowercroft, we have worked hard to ensure that both our workshop and our products minimise their environmental impact. But how can we be sure we’re making a real difference?
An Independent Study on Sustainable Windows
To understand the true environmental impact of our products and how we compare with the wider industry, we commissioned a study by Dr Stuart Walker CEng MIMechE at the University of Derby. His brief was twofold: first, to find a credible way to measure our environmental performance; second, to benchmark it against other manufacturers.
The research was fully independent and unbiased. We wanted to see whether our sustainability efforts had paid off and where we could still improve.
Dr Walker’s findings were published in two detailed reports. One compares three Gowercroft products with alternatives made from timber, aluminium and uPVC. The second focuses solely on the environmental performance of our own windows.
How Do You Measure a Window’s Environmental Impact?
Dr Walker began by identifying the relevant lifecycle stages: raw material extraction, product manufacture, packaging and transport, usage, and end-of-life treatment. He used a Life Cycle Assessment (LCA) to calculate the environmental impact at each stage.
LiWhat Is Life Cycle Assessment?
There are two types of LCA:
- Cradle to Grave: includes every stage of a product’s life, from raw materials to disposal.
- Cradle to Gate: ends when the product leaves the factory, excluding transport, installation, usage and disposal.
Because no Gowercroft windows have yet reached end of life, this study focused on a Cradle to Gate assessment. However, it’s worth noting that our windows are expected to last 80 years, double the lifespan of many uPVC windows (typically 40 years).
The Products Tested
Gowercroft Products:
- Hardwick Flush Casement in Red Grandis
- Richmond Flush Casement in Accoya®
- Acadia Flush Casement in Accoya®
Other Manufacturers:
- Mumford & Wood Conservation Casement (Hardwood)
- QKE EPPA (uPVC)
- Kawneer AA541/AA542 (Aluminium)
All comparisons were based on a window size of 1.23m x 1.48m.
Where Did the Data Come From?
The Gowercroft product data was calculated using the Building Research Establishment (BRE) LINA tool. Data for the other windows came from published Environmental Product Declarations (EPDs).
Results of the Sustainable Windows Study
Sustainable Windows: What the Results Showed
Gowercroft vs Other Timber Windows
Gowercroft had significantly lower manufacturing emissions. This is largely due to the efficiency of our workshop and equipment.
The results also showed negative emissions in two hardwood products (including our Hardwick in Red Grandis). This is because hardwood trees absorb more carbon during growth than is released in the extraction process. Accoya, being a fast-growing softwood, absorbs less carbon, so shows a small positive emission in this category.
Gowercroft vs Aluminium Windows
The aluminium-framed window had higher emissions than all timber options. Although aluminium is lighter to transport, the raw material stage is highly polluting due to bauxite extraction and energy-intensive processing. Manufacturing the final product also generates significant emissions.
Gowercroft vs uPVC Windows
In the case of uPVC, the data was less transparent. The published information only provided total emissions across several stages (A1-A3) and did not break down the figures into materials, transport and manufacturing. uPVC is lightweight, so its transport emissions are assumed to be low, but the total A1-A3 figure was the highest of all products tested.
uPVC is also made from fossil fuels. It emits carbon dioxide during production and depletes natural resources, both in terms of energy and raw material use.
Final Verdict
Dr Walker concluded:
“All products have some impact on the environment, but materials and manufacturing methods have a significant impact on the level of these emissions. The three Gowercroft window products considered in this comparison have been found to have lower emissions than comparable products manufactured by other timber window manufacturers, and significantly lower emissions than those made from Aluminium and uPVC… End of life treatment is also excluded from this comparison but should be borne in mind, particularly in the uPVC case, considering the relatively short lifetime of this product.”
In short, Gowercroft windows performed better than all other options tested when it came to cradle-to-gate emissions.