Windows: why the frame matters more than the glass

Buyers spend their attention on glass — double glazing, coatings, tints — and sign off the frame system in a line. Then they live with a window that whistles in the monsoon and lets dust through in April. Glass is a surface; the frame is an assembly of joints, gaskets, drainage channels and hardware, and it is the assembly that fails.

For a coastal or high-rain city, ask about drainage design specifically: where does water that gets into the frame go, and does it get out again. Good systems drain deliberately. Cheap ones rely on sealant, and sealant has a life measured in years.

uPVC and aluminium both work. uPVC insulates better and costs less; good thermally-broken aluminium is stronger, holds larger spans, and looks slimmer. The failure mode is different too: uPVC discolours and sags if the reinforcement inside is skimped, aluminium conducts heat if the thermal break is token.

Whatever the system, insist on a water and air test on one installed unit before the rest go in. It is a half-day and it settles the question while it is still cheap to settle.

Whatever the system, insist on a water and air test on one installed unit before the rest go in.