AC pipes sweating and dripping in summer — is it the insulation, and what makes re-lagging actually last in Dubai?

Short answer: it's condensation, not a leak — and yes it's the insulation. The copper carries refrigerant that's far colder than Dubai's warm, humid air, so wherever the insulation is thin, gapped, or has soaked up water, moisture in the air condenses straight onto the cold metal and drips. Those brown ceiling stains are that drip, not a plumbing leak. The reason your re-lag only lasted two years is almost always the material and the workmanship, not the pipe.

Why it fails and what a proper re-lag uses: - The physics: the higher the relative humidity, the more the cold pipe sweats — which is why it's a summer problem here. The insulation's whole job is to keep humid air off the cold surface. - Right material: closed-cell insulation (rigid or elastomeric) — it doesn't absorb water. Cheap open-cell foam wets out, loses its R-value, and then the pipe sweats inside the lagging, which is why it comes back. Manufacturers like Kingspan make the closed-cell products this needs. - Right thickness: too thin and the surface still drops below dew point. It has to be the correct wall thickness for the pipe and the climate. - Sealed as a vapour barrier: every seam and joint glued/taped so humid air can't track in at the gaps — the #1 workmanship failure. - UV jacket outdoors: on the outdoor run, sun destroys bare insulation in a year or two; it needs cladding or a UV-rated jacket.

So it's not a leak and it's not the pipe — it's pipe lagging done cheap. A proper AC pipe insulation job in closed-cell, correct thickness, sealed seams and a UV jacket lasts many years and is far cheaper than repainting stained ceilings every summer. (Same condensation story as the Muhaisnah ceiling-pipe sweating thread.)