Building thermal insulation · Glass wool
SCG STAY COOL
- Thickness
- 75–150 mm
- Thermal resistance (R)
- 1.79 m²·K/W (75 mm)
What is glass wool and what is it used for?
In short
Glass wool (fiberglass) is insulation made from molten glass spun into fine fibres and held together with a binder. The small air pockets between the fibres slow heat transfer and absorb sound, so it is common in roofs, ceilings, HVAC ducts, hot and chilled-water pipes and sound-absorbing panels. Real performance depends on the product, thickness, density, facing and installation.
- 1Raw material: glass wool uses glass (including recycled glass) and sand; stone wool uses volcanic rock such as basalt — proportions vary by manufacturer
- 2Melted at high temperature and spun into fibres
- 3Formed into rolls, boards or pipe sections — check each product's datasheet for its actual properties; colours here only tell the materials apart
What is glass wool made from?
The main raw materials are sand, limestone, soda ash and recycled glass (cullet). They are melted in a high-temperature furnace, spun into fibres finer than a human hair, sprayed with a binder and cured into rolls or boards.
What insulates is not the glass itself but the still air trapped between the fibres. If the insulation is squashed flat or gets wet, its performance drops.
Common forms
| Form | Description | Typical uses |
|---|---|---|
| --- | --- | --- |
| Roll / blanket | Soft, can be laid or wrapped; often foil on one side or fully encapsulated | Under roofs, on ceilings, duct wrap |
| Board | Stiffer, holds its shape | Duct liner, lightweight walls |
| Pipe section | Pre-formed half-shells sized to the pipe | Hot-water pipes, some steam lines within the rated range |
| Acoustic panel | Fabric or glass-tissue faced | Meeting rooms, cinemas |
What is it used for?
- Roof and ceiling insulation — reduces heat coming down from the roof space. See how to choose roof insulation
- Air-conditioning — wrapped outside ducts (duct wrap) or lined inside (duct liner) to reduce energy loss and help reduce noise in the duct
- Pipe insulation — pre-formed sections for pipes within the temperature range the maker states, such as SCG PCI, whose service range is given in its catalogue
- Acoustics — fitted in lightweight wall cavities as part of a sound-insulating wall system, or made into panels to reduce echo. See soundproofing vs sound absorption
What to know before choosing
- The values to check are thermal conductivity (λ) or R-value at the actual thickness, the service temperature and the fire-test results of that specific product — not of "glass wool" in general
- Facings matter. Foil reflects heat and acts as a vapour barrier, but it can also change the product's fire-test result; check the result for the faced product
- Service temperatures differ widely between products. Glass wool for ducts and pre-formed sections for hot pipes are designed differently. See what is service temperature
Installation
The fibres can cause temporary irritation of the skin, eyes and airways. Wear gloves, long sleeves, eye protection and a dust mask, and follow the manufacturer's safety data sheet (SDS). IARC places "insulation glass wool" in Group 3 (not classifiable as to carcinogenicity to humans).
How is glass wool different from stone wool?
Both are mineral wools, but their raw materials, service temperatures and typical uses differ. Read stone wool vs glass wool and what is stone wool.
Sources
- EURIMA — How is mineral wool insulation made?
- Saint-Gobain ISOVER Technical Insulation — Glass wool
- IARC Monographs Volume 81: Man-made Vitreous Fibres (2002)
- SCG — SCG Insulation for Industrial : Pipe (PCI) catalogue and SCG STAY COOL brochure
Related products
Categories and example products for this topic
- SCG STAY COOL — As a roll: foil-encapsulated glass wool laid on ceilings against heat
- SCG PCI / PCIF — As a pipe section: for hot and cold steel pipes, service range 10–540 °C
- Micro Duct Wrap FRK — As a foil-faced wrap: outside AC ducts, in several densities and thicknesses
- SCG Cylence Armax — As a ceiling tile: white-vinyl-faced glass wool laid in T-bar grids to cut reverberation
Pipe insulation · Glass wool
SCG PCI / PCIF
- Pipe size
- ½–18 in
- Thickness
- 25–50 mm
- Service temp.
- 10 – 540 °C
Duct and HVAC insulation · Glass wool
Microfiber Micro Duct Wrap FRK
- Thickness
- 25–50 mm
- Density
- 16–32 kg/m³
- Thermal conductivity (λ)
- 0.033–0.038 W/m·K
