50mm
Knauf Ceiling Roll
- Material R-value
- R1.25
- Roll coverage
- 22.80 m²
Knauf Earthwool · Glass mineral wool
Glass Wool Insulation for South African Homes
Explore Knauf Earthwool glasswool insulation in four ceiling roll thicknesses. Compare thermal R-values and roll coverage, understand the material, and choose the product that suits your project.
Know your insulation
What is glass wool insulation?
Glass wool is an insulation material made from fine glass fibres. The fibres form a lightweight structure that traps air and slows heat transfer. Installed above a ceiling, it helps limit heat entering the rooms below in summer and escaping in winter.
Our range consists of four Knauf Earthwool Ceiling Rolls made from glass mineral wool. Each thickness has its own thermal resistance and coverage, so the right choice depends on your project requirements and ceiling area.
Our complete range
Four Knauf glasswool ceiling rolls
Choose from 50mm, 75mm, 100mm and 135mm. All four are glass mineral wool ceiling rolls; the thickness changes the material R-value and the area covered by each roll.
75mm
Knauf Ceiling Roll
- Material R-value
- R1.88
- Roll coverage
- 15.36 m²
100mm
Knauf Ceiling Roll
- Material R-value
- R2.50
- Roll coverage
- 12.12 m²
135mm
Knauf Ceiling Roll
- Material R-value
- R3.38
- Roll coverage
- 9.00 m²
R-values above refer to the insulation material, not the complete roof assembly. Confirm the required performance for your building before choosing a thickness.
Make a useful comparison01 / THERMAL PERFORMANCE 02 / QUANTITY & COVERAGE
Choosing glass wool for your ceiling
Start with the R-value
R-value measures resistance to heat flow. Within these four Knauf rolls, a higher R-value means greater thermal resistance. The 135mm roll offers the highest material R-value in our range at R3.38.
A thinner roll is not automatically suitable for every ceiling. Check the project's thermal requirements and any existing insulation before deciding. Read our ceiling insulation guide and installation options.
Compare the area each roll covers
Measure the ceiling area in square metres, divide it by your selected roll's coverage and round up to a whole roll. Allow for the roof layout and cutting waste when planning your order.
For example, 60 m² divided by 12.12 m² per 100mm roll is 4.95 rolls: a starting estimate of five rolls before any extra allowance. Use our Knauf roll calculator to compare quantities.
Plan your purchase
Glass wool insulation prices
Compare the cost of insulating the same area at the R-value your project needs. The cheapest roll is not necessarily the lowest cost per square metre, because roll coverage differs by thickness.
For a material cost comparison, divide the current roll price by its coverage. Then calculate the whole rolls required and add delivery and installation where applicable.
Find the right roll price
Our price page brings the four Knauf products together. For a project quote, send your suburb, ceiling area and preferred thickness, and tell us whether you need supply only or installation.
Understand the difference
Glass wool and stone wool
Glass wool and stone wool belong to the wider mineral wool insulation family. Glass wool is made from glass fibres; stone wool uses fibres made from rock-based raw materials.
They are different products, so compare their declared thermal performance, intended application and installation requirements rather than choosing by material name alone.
Your questions answered
Glass wool insulation FAQs
Is Earthwool glass wool insulation?
The Knauf Earthwool Ceiling Rolls supplied on this website are glass mineral wool insulation. Our range includes four thicknesses: 50mm, 75mm, 100mm and 135mm.
Can I use fibreglass insulation above a ceiling?
Our Knauf Ceiling Rolls are designed for ceiling insulation. The required thickness depends on the building's thermal requirements. Installation quality matters: the insulation should form a continuous layer without avoidable gaps or compression and follow the manufacturer's installation instructions.
Which glass wool thickness should I choose?
Start with the required thermal performance, then compare R-value, coverage and total material cost. The 135mm roll has the highest material R-value of the four products at R3.38, but your installer should confirm the appropriate specification for your ceiling and any existing insulation.
Does glass wool help with sound?
Glass mineral wool can absorb sound, but the result depends on the complete ceiling or building assembly. A thermal R-value is not a soundproofing rating. Read more about acoustic insulation and discuss the source of the noise before choosing a solution.
Can glass wool be added over existing ceiling insulation?
A top-up may be possible after checking the existing insulation's condition, thickness and coverage. Ask an installer to assess the roof space and the additional thermal performance needed before ordering. Damp, damaged or poorly fitted insulation needs assessment first.
How do I get a glass wool insulation quote near me?
Send us your suburb and ceiling area, along with the thickness you are considering. Let us know if you need supply only or installation. For installation enquiries in Johannesburg or Pretoria, include whether the roof space is accessible and whether insulation is already present.
Ready to get started?
Looking for Glass Wool Insulation?Request a Knauf Earthwool Quote.
Get a quote for 50mm, 75mm, 100mm or 135mm Knauf Earthwool glass wool insulation. Send your ceiling area, preferred thickness and delivery location, and tell us whether you need supply only or installation.
- Four thicknesses
- Supply-only quotations
- Installation enquiries