Double Glazing Comparisons
Three decisions decide most of your bill. Here is each one weighed up, with a clear verdict at the end.
Choosing windows comes down to a handful of either-or calls: which frame material, whether to fit them yourself or pay for fitting, and how many panes of glass. Each comparison below lays out the numbers from our 2026 cost data, weighs the trade-offs and ends with a Best Buy, Worth it, It depends or Skip it verdict. If you have not settled on a budget yet, the calculators will give you a price range for either side of each comparison.
uPVC vs Aluminium
Cost, look, lifespan and maintenance compared. uPVC wins on price, aluminium on slim frames.
Supply-Only vs Fully Fitted
What you save going supply-only, and why the FENSA certificate usually tips it back.
Double vs Triple Glazing
When the extra pane is worth the 20 to 30% premium, and when double is plenty.
Where to start
If your main worry is cost, read uPVC versus aluminium first, because the frame is the biggest price lever. If you are handy and tempted to buy the units yourself, read supply-only versus fully fitted before you commit, as the missing FENSA certificate can cost you at resale. And if an installer is pushing triple glazing, double versus triple tells you when it is genuinely worth the extra.