Glass wool is most commonly known for insulation in ceilings of residential buildings.But it also finds its extensive application in air conditioning systems insulation,HVAC insulation,Pipe insulation,Dry wall insulation,Indusrtial roofing insulation and high performance sound proofing.Glass wool products are non-combustible and positioned for operating temperatures upto 550c.It is light weight,Easy to install and non corrosive to metals.Glass wool is considered to be the most economic,Effective and environmental friendly insulation product.
Thermal and acoustic insulation in one material
Working range −195°C to +250°C
Very low thermal conductivity (~0.035 W/m·K)
Non-combustible — and the most economical insulation we supply
Glass wool is the workhorse insulation of industry and building services. It is a mat of fine glass fibres bonded with a thermosetting resin, supplied in rolls, and it does two jobs at once that most materials only do one of: it is an excellent thermal insulator and an excellent acoustic absorber. That combination is why it lines HVAC ducting, plant rooms, cold stores and pipe runs almost universally.
Its thermal conductivity is around 0.035 W/m·K — genuinely better, per millimetre, than ceramic fibre. Where glass wool loses is temperature: the practical ceiling for standard grades is about 250°C. That single number is what determines whether glass wool is the right choice or a serious mistake.
Two mistakes are worth naming plainly, because we see both regularly. The first is fitting glass wool to something too hot — a furnace, a superheated steam line — where the binder degrades and the insulation fails. The second, and more expensive, is over-specifying: buying ceramic fibre wool for a 100°C duct or a cold store, where glass wool would insulate better, absorb sound as well, and cost a fraction as much. Below 250°C, glass wool is not the budget option — it is the correct option.
It also performs at the other extreme, down to about −195°C, which is why it is standard for cold storage, chilled-water lines and cryogenic pipework.
Specifications
Typical properties for resin-bonded glass wool insulation. Thermal conductivity and temperature limit vary somewhat with density and binder grade — high-binder specialist grades reach higher temperatures than the standard figure below.
Property
Value
Test Standard
Material
Glass mineral wool, resin-bonded
—
Working Temperature Range
−195°C to +250°C
—
Max Temperature (special grades)
up to ~450°C (high-binder grades)
—
Thermal Conductivity
~0.035 W/m·K (at ambient)
ASTM C177 / ISO 8301
Density
10 – 100 kg/m³
—
Thickness
25 mm and 50 mm
—
Roll Size — 25 mm
1.2 m wide × 20 m long
—
Roll Size — 50 mm
1.2 m wide × 15 m long
—
Acoustic Performance
Excellent — high sound absorption coefficient
ISO 354
Combustibility
Non-combustible (glass fibre)
ASTM E136
Binder
Thermosetting resin (this is the temperature-limiting component)
—
Water Absorption
Non-hygroscopic, but wetting destroys insulating value until dry
—
Chemical Stability
Chemically inert; resists most industrial atmospheres
—
Vapour Permeability
Open structure — a vapour barrier is required in cold service
—
Form
Flexible roll; faced or unfaced
—
Facing Options
Plain, aluminium foil, glass tissue (to order)
—
Rot / Vermin Resistance
Does not rot; does not sustain vermin or fungal growth
—
Properties in Detail
Thermal Properties
Working Range
−195°C to +250°C
Thermal Conductivity
~0.035 W/m·K
Cryogenic Capable
Yes — down to −195°C
Temperature Limiter
The resin binder, not the glass
Combustibility
Non-combustible
Acoustic Properties
Sound Absorption
Excellent
Typical Use
Plant rooms, duct lining, partitions
Why It Works
Open fibrous structure dissipates sound energy
vs Ceramic Fibre
Far better acoustically, and far cheaper
Physical Properties
Density
10 – 100 kg/m³
Thickness
25 mm / 50 mm
Form
Flexible roll
Moisture
Must stay dry to insulate — vapour barrier needed in cold service
Manufacturing
Glass wool is made by melting glass (typically with a high recycled-glass content) and spinning the melt into extremely fine fibres, which are then sprayed with a thermosetting resin binder and cured in an oven. The result is a light, resilient mat with a very high void fraction — and it is that trapped, still air, not the glass itself, that does most of the insulating.
The binder is the temperature-limiting component, and this is the single most useful thing to understand about glass wool. The glass fibre itself would tolerate considerably more heat; it is the organic resin holding the mat together that degrades at around 250°C. This is why specialist high-binder grades can reach higher temperatures, and why exceeding the limit causes the insulation to break down and lose structure rather than simply "getting hot".
Density is set by how much fibre is packed into a given thickness. Higher density gives slightly better thermal performance and noticeably better acoustic absorption, at higher cost and weight.
Roll Sizes & Coverage
Glass wool is supplied in two thicknesses. Both come on 1.2 m-wide rolls — note these are much larger rolls than ceramic fibre, which is why glass wool covers area so economically.
Thickness
Roll Width
Roll Length
Area per Roll
Typical Use
25 mm
1.2 m
20 m
24.0 m²
Duct wrap, acoustic lining, light thermal duty
50 mm
1.2 m
15 m
18.0 m²
Main thermal insulation, cold stores, pipe lagging
Thicknesses other than 25 mm and 50 mm are built up by layering. Our Wool Quantity Calculator works out the roll count for your area, and the Insulation Thickness Calculator will tell you what thickness you actually need for your operating temperature.
Applications
Glass wool is the default insulation for everything below 250°C — thermal, acoustic, or both.
HVAC Duct InsulationDuct wrap and internal duct lining. It does double duty here: cutting heat gain/loss from the air stream and absorbing the fan and airflow noise that would otherwise carry through the building.
Pipe LaggingHot and chilled water lines, steam condensate and process pipework below 250°C. Reduces heat loss, prevents condensation on cold lines, and protects personnel from hot surfaces.
Cold Storage & Chilled RoomsWall, ceiling and refrigeration pipework insulation, performing well into sub-zero temperatures. A vapour barrier is essential in cold service — without one, moisture condenses inside the insulation and destroys it.
Acoustic & Plant Room LiningSound absorption in plant rooms, generator enclosures, partitions and machinery housings. This is where glass wool has no economical rival — ceramic fibre is both worse acoustically and far more expensive.
Boiler & Tank Insulation (below 250°C)Casings, tanks and vessels operating within the temperature limit. Above 250°C, switch to ceramic fibre — the binder in glass wool will degrade.
Building Envelope InsulationRoof, wall and cavity insulation in industrial and commercial construction, where its combination of low cost, non-combustibility and acoustic value is hard to beat.
Industries
Why Glass Wool is specified in each of the industries we serve.
HVAC & Building Services
HVAC is where glass wool is most completely at home, because building services need exactly the two things it does simultaneously. Ductwork must be insulated thermally, or conditioned air gains or loses heat on its way through the building and the plant works harder than it should. But ductwork is also a noise path — fan noise and airflow turbulence travel along it and emerge in occupied spaces — and glass wool’s open fibrous structure absorbs that sound as effectively as it resists heat transfer. A single material therefore solves both problems in one installation, which is why duct wrap and duct lining are glass wool almost by default. The practical failure mode to watch for is compression: insulation that has been squashed at a joint or a support has lost the trapped air that does the insulating, and will leak both heat and sound at exactly that point.
Cold Storage & Food Processing
Glass wool performs down to about −195°C, which makes it entirely suitable for cold rooms, freezer envelopes and chilled-water and refrigeration pipework. But cold service introduces a problem that does not exist in hot service, and it catches people out: vapour drive. Warm, humid ambient air pushes moisture into the insulation towards the cold surface, where it condenses. Wet glass wool insulates very poorly, and once it is wet it stays wet. A properly sealed vapour barrier on the warm side is therefore not an optional extra in cold storage — it is the difference between insulation that works and insulation that quietly fails within a season. Fit the barrier on the warm side, seal every seam and penetration, and the same material that insulates a boiler room will happily insulate a freezer.
Power Plants
A power station has a very wide temperature range across its systems, and the economic play is to insulate each part with the right material rather than defaulting to the expensive one everywhere. Glass wool covers everything below 250°C: feedwater and condensate lines, general ducting, tanks, plant-room acoustic treatment and personnel protection on warm surfaces. It is markedly cheaper than ceramic fibre and actually insulates better per millimetre in that range. Where it must not be used is on the hot side — superheated steam lines, boiler casings, flue gas paths — because the resin binder degrades above its limit and the insulation breaks down. The rule of thumb worth applying across the whole plant is simple: below 250°C use glass wool, above 600°C use ceramic fibre, and confirm the grade with us in between.
Textile & General Manufacturing
Process plant, steam distribution below 250°C, hot water systems and compressed air lines all lose heat continuously if left bare, and in a mill running around the clock that loss is significant and entirely avoidable. Glass wool is the economical answer for all of it. The other half of the value in a manufacturing environment is acoustic: machinery halls, compressor rooms and generator enclosures are noisy, and glass wool lining is one of the cheapest and most effective ways of bringing sound levels down. It is also non-combustible, which matters in a factory setting. Where a mill has genuinely hot equipment — a boiler, a furnace, a dryer running above the limit — that specific equipment needs ceramic fibre, but the great majority of a factory’s insulation requirement sits comfortably inside glass wool’s range.
Glass Wool vs Other Insulation
Below 250°C, glass wool is not the cheap compromise — it is genuinely the best-performing choice, and the cheapest. Above it, it is simply the wrong material.
Property
Glass Wool
Ceramic Fiber Wool
Rock / Mineral Wool
Ceramic Board
Max Temperature
~250°C
1260°C class (~1100°C cont.)
~600°C
1260°C
Min Temperature
−195°C
Ambient
Ambient
Ambient
Thermal Conductivity
~0.035 W/m·K (best of these)
0.10 – 0.31 W/m·K
~0.040 W/m·K
~0.09 W/m·K
Acoustic Absorption
Excellent
Fair
Excellent
Poor
Cryogenic Service
Yes
No
No
No
Roll Coverage
Large (1.2 m wide)
Small (610 mm wide)
Medium
Rigid panels
Relative Cost
Low — the cheapest
High
Medium
High
Choose It For
HVAC, cold storage, acoustics, <250°C
Furnaces, kilns, >600°C
Mid-range to 600°C
Rigid hot face
Advantages & Limitations
Advantages
Excellent thermal conductivity (~0.035 W/m·K) — better per millimetre than ceramic fibre.
Excellent acoustic absorption — solves thermal and noise problems with one material.
Very wide low-temperature capability, down to about −195°C (cryogenic-capable).
Non-combustible.
The most economical insulation we supply, by a wide margin.
Large roll sizes (1.2 m wide) cover area quickly with fewer joints.
Light, flexible, easy to cut and fit around ducts and pipework.
Does not rot, and does not sustain vermin or fungal growth.
Limitations
Hard ceiling of about 250°C for standard grades. The resin binder degrades above this — the insulation breaks down rather than merely getting hot. Do not use it on furnaces, superheated steam or flue gas.
Loses almost all insulating value when wet, and does not readily recover in situ. In cold service a sealed vapour barrier is mandatory, not optional.
Compresses easily — and compressed glass wool has lost the trapped air that does the insulating. Do not squash it at joints, supports or behind cladding.
Fibres and dust irritate skin, eyes and airways during installation — gloves, eye protection and a dust mask are required.
Lower mechanical strength than rigid boards; needs support and protection where it can be knocked or walked on.
Open structure requires a facing or cladding where it is exposed to weather or air movement.
Installation, Storage & Maintenance
Installation
Fit the insulation without compressing it — compression is the most common installation error and it directly destroys performance, because the trapped still air is what insulates, not the glass. Butt joints tightly rather than leaving gaps, and stagger joints between layers when building up thickness. In cold service, fit a continuous vapour barrier on the warm side and seal every seam and penetration; without it, moisture will condense inside the insulation and ruin it. Wear gloves, eye protection and a dust mask when cutting.
Storage
Store rolls dry, off the floor, in their original wrapping and under cover. Water is the enemy of glass wool: wet insulation loses most of its value and will not simply dry out and recover once installed behind cladding. Keep rolls compressed only as packed — do not stack heavy items on them, as prolonged compression can leave a permanent set.
Maintenance
Glass wool is essentially maintenance-free provided it stays dry and uncompressed. The things to inspect are exactly those two: look for water ingress (staining, sagging, a cladding leak upstream) and for areas that have been crushed by supports, foot traffic or subsequent trades. Wet or compressed insulation is not insulating — replace those sections rather than leaving them in place, and fix the cause.
Buying Guide
What to tell us so we quote the right grade first time.
Your operating temperature — is it under 250°C? This is the whole decision. Under 250°C glass wool is the right and cheapest answer. Above it you need ceramic fibre, and no thickness of glass wool will fix that.
Thermal, acoustic, or both? Glass wool does both. If noise is a major driver, tell us — higher-density grades absorb sound significantly better.
Hot service or cold service? Cold service changes the specification: you need a vapour barrier, and it is essential rather than optional. Tell us it is a cold application.
Faced or unfaced? Foil-faced glass wool provides a built-in vapour barrier and a finished surface. Tell us if the insulation will be exposed or needs a facing.
Density. Higher density means slightly better thermal and noticeably better acoustic performance, at more cost and weight. For plain thermal duty, standard density is usually sufficient.
Standards & Compliance
ASTM C177 / ISO 8301 — thermal conductivity measurement.
ASTM E136 — non-combustibility.
ISO 354 — measurement of sound absorption.
Supplied as resin-bonded glass mineral wool in 25 mm and 50 mm thicknesses; densities from 10 to 100 kg/m³ to order.
Handling note: glass fibres and dust irritate skin, eyes and the respiratory tract during installation. Gloves, eye protection and a dust mask should be worn when cutting or fitting.
Standard grades work from about −195°C up to +250°C. Specialist high-binder grades reach higher (up to around 450°C). The 250°C figure is the practical limit you should design to unless we have specifically supplied a high-temperature grade.
What actually limits the temperature — the glass?
No, the binder. The glass fibre itself would tolerate more heat; it is the thermosetting resin holding the mat together that degrades at around 250°C. Above that, the insulation breaks down structurally rather than just getting hot.
Can I use glass wool on a furnace or boiler?
Not on a furnace, and not on the hot side of a boiler. Above 250°C you need ceramic fibre wool. Glass wool is fine for the cooler parts of a boiler house — feedwater lines, tanks, ducting below the limit.
Is ceramic fiber better than glass wool?
Only above 250°C. Below that, glass wool actually insulates better per millimetre (0.035 vs 0.10+ W/m·K), absorbs sound far better, and costs a fraction as much. Buying ceramic fibre for a low-temperature duct or cold room is a genuine and expensive mistake.
What are the roll sizes?
25 mm comes as 1.2 m wide × 20 m long (24 m²). 50 mm comes as 1.2 m wide × 15 m long (18 m²). These are much larger rolls than ceramic fibre, which is part of why glass wool covers area so economically.
How many rolls do I need?
Use our Wool Quantity Calculator — give it your area, thickness and layer count and it returns the roll count and weight.
Does glass wool insulate against sound as well as heat?
Yes, and this is one of its main advantages. Its open fibrous structure absorbs airborne sound as effectively as it resists heat transfer, which is why the same material is used for duct lining, plant rooms and acoustic partitions.
What happens if glass wool gets wet?
It loses most of its insulating value, and it does not readily recover once it is installed behind cladding. Water is the main thing that destroys a glass wool installation. Keep it dry in storage, and in cold service fit a vapour barrier.
Why do I need a vapour barrier in cold storage?
Because warm humid air drives moisture into the insulation towards the cold surface, where it condenses. Wet insulation does not insulate. A sealed vapour barrier on the warm side is essential in any cold application — it is not an optional extra.
Which side does the vapour barrier go on?
The warm side — always. In a cold room that means the outside (ambient) face, not the cold face. Seal all seams and penetrations, because a barrier with gaps in it is not a barrier.
Why does compressed glass wool not work?
Because it is the trapped still air, not the glass, that does most of the insulating. Squashing it at a joint, a support or behind tight cladding removes that air and destroys performance at exactly that point. Fit it without compression.
Is glass wool non-combustible?
Yes — the glass fibre is non-combustible. This is one reason it is used so widely in building services and industrial plant rooms.
Can it be used at cryogenic temperatures?
Yes, down to about −195°C, which is why it is standard for cryogenic and chilled pipework as well as cold rooms. The vapour barrier requirement is even more critical at these temperatures.
What density should I choose?
Higher density gives slightly better thermal performance and noticeably better acoustic absorption, at higher cost and weight. For plain thermal duty, standard density is usually fine. If noise control is a major driver, go denser.
Should I get faced or unfaced glass wool?
Foil-faced provides a built-in vapour barrier and a finished surface — useful in cold service and where the insulation is exposed. Unfaced is fine where it will be covered by cladding and a separate barrier is fitted.
Is glass wool safe to handle?
The fibres and dust irritate skin, eyes and airways during cutting and fitting. Wear gloves, eye protection and a dust mask. It is not in the same hazard class as old ceramic fibre linings, but it is unpleasant to work with unprotected.
Does glass wool rot or attract vermin?
No. It does not rot, and it does not sustain fungal growth or provide food for vermin.
How thick should the insulation be?
That depends on your operating temperature, ambient temperature and what surface temperature you are targeting. Our Insulation Thickness Calculator will size it for you, and the Heat Loss Calculator will show what you save.
Can I use glass wool for pipe lagging?
Yes — hot and chilled water, condensate and process lines below 250°C. It reduces heat loss, prevents condensation on cold lines, and protects personnel from hot surfaces.
How long does glass wool last?
Effectively the life of the installation, provided it stays dry and uncompressed. Those two things — water and crushing — are what kill it, not age.
Need a quote or a spec check?
Send us your operating conditions and we will confirm the right grade for the job.
