UPVC windows vs aluminium thermally broken

uPVC is a plastic window, sometimes with steel reinforcement, thermally broken is an aluminium window which has the profiles separated, between outside and inside and these are joined with plastic.
Both rely upon the low conductivity of plastic for their energy performance.

The advantage of uPVC is the lower U value, its disadvantages are that uPVC has a high coefficient of linear expansion, it melts at 170 deg, C. And uPVC becomes brittle over time, making maintenance difficult. The high expansion rate for me means that large sashes and moving panels require space to move, and they can bind or stick. The low temperature of melting seems to negate their claim of suitability for BAL29. White would be the only colour to work with due to the absorption of solar energy by the darker colours which will exacerbate the expansion problem, and likely the ageing of the uPVC.

Thermally broken is just a design type, on its own, it does not represent that the window is any more energy efficient than any other. The key to its performance is the Uw, look at the Uw (in WERS.net). I say this because our EcoTech window outperforms most thermally broken windows, and though EcoTech is not thermally broken, its design is far superior. These figures are produced by independent NATA laboratories and audited by the Window Energy Rating Scheme, so this is a levelling factor.

Cost wise, uPVC and thermally broken would be on par, EcoTech would be about 40% cheaper than thermally broken windows.

There are many more aluminium window companies in Melbourne than all the others put together, Aluminium would be 90% of the market.