Double Glazing Comparisons
The either-or calls that decide most of your bill, from frame material to glass spec, each 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 10 to 20% premium, and when double is plenty.
uPVC vs Timber
The value pick against the heritage choice, on cost, looks, lifespan and upkeep.
Aluminium vs Timber
Two premium frames for very different homes: slim and modern versus period.
Casement vs Sash
The most common style against the period classic, on cost, seal and maintenance.
Repair vs Replace
A misted unit costs £55 to £145; a new window £400 to £1,000. How to decide.
Secondary vs Double Glazing
Keep your original frames or replace them, weighed on cost, heat loss and noise.
A-Rated vs A+ Glass
When stepping up from the A-rated standard to A+ or A++ triple glazing pays off.
Argon vs Krypton Gas
Why argon is the standard fill and when the pricier krypton upgrade is worth it.
Double Glazing vs Solar
Which gives the better energy return for your money, and why it is not either-or.
uPVC vs Composite Doors
How each is built, 2026 fitted prices, and why security comes from the cylinder, not the material.
uPVC Window Brands Compared
REHAU, VEKA, Liniar and seven more on the makers' own published specs. No scores, no winner.
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. Comparisons assume you already know the basics, so if you want the plain double glazing questions answered first, on cost, grants, lifespan and building regulations, start with Double Glazing Questions Answered.