Glass Wool Insulation for Ducts, Ceilings and Walls

What it is

Mineral fibre spun from molten glass, bound into rolls, slabs and pipe sections. Lighter and cheaper than rock wool, with slightly better thermal conductivity per millimetre and lower temperature tolerance.

Specification at a glance

Property	Typical specification
Standard	IS 8183, bonded mineral wool
Thermal conductivity	Approximately 0.032 — 0.040 W/mK
Density range	12 — 48 kg/m³ typical
Fire class	A1 / A2 to EN 13501-1 by product and facing
Facing	Plain, reinforced foil, tissue, or black glass tissue
Service temperature	Lower than rock wool

Density by application

Application	Density
Duct wrap, external	16 — 24 kg/m³, foil faced
Duct lining, internal acoustic	32 — 48 kg/m³, tissue faced
Ceiling plenum blanket	12 — 16 kg/m³
Partition acoustic infill	24 — 48 kg/m³
Pipe section	Preformed, density by diameter

Where it belongs on a fit-out

Duct wrap on conditioned-air and chilled-water ducts, foil faced for vapour control. Internal duct lining where fan and airflow noise must be absorbed before it reaches the occupied space. Partition infill between meeting rooms and tenancies, where the acoustic rating of the partition depends on it. Above ceiling, as a plenum blanket where the slab soffit is uninsulated.

Where projects go wrong

• Unfaced insulation on a cold duct. Condensation forms inside the insulation, performance collapses, and ceilings stain below.
• Foil joints untaped. The vapour barrier is only continuous if the laps are sealed; an untaped lap is an open path.
• Insulation compressed by a cable tray or hanger. Compression reduces thickness and performance at exactly the points nobody inspects.
• Glass wool used as a cavity barrier. It is not the specified material for that duty; rock wool is.

Standards referenced

Bonded mineral wool under IS 8183. Reaction-to-fire classification to EN 13501-1. Services and envelope insulation requirements under ECBC 2017.