Why does my window glass fog on the outside, not inside?

In tropical Singapore your interior is cooler than outdoor air. Outdoor humidity condenses on the cool glass exterior — same physics as a cold drink glass sweating. Normal; doesn't damage anything.

Will Shield22 Pro make my aluminium frame look different?

Applied thinly on interior edges only. Matte white or over-painted to match. Visible only on very close inspection.

Is anti-fog film the same thing?

No. Anti-fog film reduces surface tension so water spreads instead of beading — you get a wet film instead of drops. Shield22 Pro stops the condensation from forming.

Do I need to replace mouldy curtains?

If mould is on 20%+ of the fabric or penetrates the weave, yes. Small hem-line spots can be treated with oxygen bleach.

Anti-Condensation Cluster

Window & Glass Condensation in Singapore — Frames, Sills & Curtain Fix

In Singapore, window glass condensation forms on the outside when a cool interior meets 30°C humid outdoor air. Inside, condensation collects on aluminium frames and stone sills — pools of water that stain paint, ruin curtains, and grow mould on the wall below.

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Where the water is forming

Aluminium window frames (interior side) — aluminium is a strong thermal conductor. Marble/granite sills get cold from the frame and pool condensate. Curtain hems wick moisture upward and grow black mould. Glass exterior fogging in the early morning is normal in Singapore and clears — not a problem to fix.

Fix each surface

Aluminium frames + sills: Shield22 Pro coating from S$380 per window. Curtain hems: replace with lift-off design; hem 5cm above sill (free). Existing wall mould below sill: standard wall mould removal (from S$450). Draughts: re-seal frame perimeter with neutral-cure silicone from S$80 per window.

When double glazing is (and isn't) worth it

Double glazing costs S$800–1,500 per window and needs major renovation. For most Singapore homes, Shield22 Pro on the frame + curtain repositioning gets 80% of the benefit at 10% of the cost. Double glazing pays off when you're already renovating or need noise reduction more than condensation fix.

Prevention habits (free)

Run fan-only mode 15 min before/after aircon. Keep curtains open at night. Raise aircon setpoint 1°C — small dew-point margin often eliminates frame sweat.

Shield22 Pro — the coating that stops condensation at source

Thermal micro-ceramic coating that raises the surface temperature above dew point so airborne moisture stops condensing. From S$18/m². 5-year condensation-free warranty. Non-toxic, low-VOC, safe for occupied rooms.

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Related in the Anti-Condensation cluster

Frequently Asked Questions

Why does my window glass fog on the outside, not inside?: In tropical Singapore your interior is cooler than outdoor air. Outdoor humidity condenses on the cool glass exterior — same physics as a cold drink glass sweating. Normal; doesn't damage anything.
Will Shield22 Pro make my aluminium frame look different?: Applied thinly on interior edges only. Matte white or over-painted to match. Visible only on very close inspection.
Is anti-fog film the same thing?: No. Anti-fog film reduces surface tension so water spreads instead of beading — you get a wet film instead of drops. Shield22 Pro stops the condensation from forming.
Do I need to replace mouldy curtains?: If mould is on 20%+ of the fabric or penetrates the weave, yes. Small hem-line spots can be treated with oxygen bleach.