What a window is actually for.

Sound gets into a room through gaps first and glass second. A sash that presses onto a continuous gasket closes the gaps. One that only touches its frame does not. This is why a closed casement is usually quieter than a slider, and why gasket continuity matters more than profile thickness.

What you notice is not silence. The sharp sounds, like horns, brakes and voices, drop away. What is left is a low hum that most people stop noticing.

uPVC conducts heat poorly, and the chambers inside the profile trap still air, which conducts it even less. That is the whole mechanism. More chambers usually means a slower path for heat.

You are more likely to notice it in how long a cooled room stays cool than on a thermometer. The glass matters as much as the frame, so the two have to be specified together.

Every window lets some water past its outer line in driving rain. A well-made frame expects this and drains it back out. A badly made one holds it until it shows up as damp on the wall.

Dust behaves like noise: it comes in through gaps. The same gasket that quietens a room keeps the sills cleaner.

uPVC does not rot, corrode or need repainting. Keep the gasket clean and the drainage slots clear, and check the hardware now and then.

The real risk is UV. Under strong Indian sun, a poorly pigmented profile yellows and turns chalky. Titanium dioxide loading prevents this, and it is the specification most worth asking any supplier about.