How to Choose uPVC Windows

Chambers are the sealed air pockets inside a uPVC profile. Five-chamber frames are the modern minimum; six- and seven-chamber systems (Eurocell Modus, Rehau Total 70) run cooler on the inside and reduce condensation. Every profile should have a galvanised steel reinforcement inside — ask to see the section drawing. Frames without reinforcement can warp on large casements.

Look for Argon-filled units with warm-edge spacer bars and low-E coatings. Warm-edge spacers (Swisspacer, Thermix) are the single biggest upgrade over old aluminium-spaced units — they cut edge condensation dramatically. Ask for the glass unit width — a 28mm unit outperforms a 20mm one and both fit most modern profiles.

The window energy label (A++ to G) is a marketing convenience — it bundles U-value, solar gain and air leakage into one letter. For a real comparison, ask for the whole-window U-value in W/m²K. A modern uPVC window should achieve 1.2–1.4. Anything above 1.6 is out of date; anything below 1.0 needs triple glazing.

Hinges, espagnolette rods, handles and gaskets are the parts that fail. Specify Yale, Roto or Maco espag mechanisms, stainless-steel friction hinges rated for the sash weight, and Kitemarked handles with lockable keeps on ground-floor openers. Cheap hardware fails at 8–10 years even on a good frame.

On completion, check: even 3mm gap around every opener, sash closes with light finger pressure (not a shove), no draught felt at the corner joints, silicone bead neat and continuous, and internal beads (not external) holding the glass in place. External beads let a determined burglar remove the pane.