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Exhaust Lagging Explained
Exhaust lagging is insulation applied along an exhaust pipe to keep the heat inside it. On plant, trucks, generators and boats that is not a comfort question. It is about what the heat reaches once it leaves the pipe.
Kool Wrap has supplied heat protection in Australia since 1995, to workshops, fleets, marine operators and mine sites. This page covers what lagging is, how it differs from the other two things people call it, and which material suits which temperature.
Lagging, wrap and blankets are three different things
The words get used interchangeably and they describe three different products.
| Term | What it is | Does it come off? |
|---|---|---|
| Lagging | Insulation applied along the length of a pipe, usually in wide woven rolls | No. It is fixed in place |
| Wrap | The same idea in narrower automotive widths | No |
| Blanket | A tailored, removable cover for one component | Yes. It unclips |
The practical difference is width and intent. Heavy duty lagging comes in 3mm rolls, 30 metres long, in 50mm, 75mm and 100mm widths. Those widths exist because covering a large-diameter pipe in 25mm automotive tape is mostly labour.
Browse exhaust heat wrap and lagging.
Which lagging material for which temperature
This is the decision people get wrong, and the cost of getting it wrong is doing the job twice.
| Material | Continuous rating | Where it belongs |
|---|---|---|
| Standard fibreglass | 540°C | General exhaust runs on trucks and plant |
| Titanium basalt | 980°C | Turbo outlets, manifolds and anything running hotter |
| Rockwool | Up to 1,000°C | Static insulation, hot pipework, ducting and plant |
| Split tube pipe insulation | Pipes up to 800°C | Pipe runs where a pre-formed tube fits faster than wrapping |
Two rules. Choose by the temperature at the hottest point of the run, not the average. And leave margin rather than matching the rating exactly.
Rockwool and the split tube insulation sit on the industrial insulation page. Titanium basalt comes in 3mm industrial rolls as well as automotive widths, on the titanium basalt page.
Why an exhaust runs hotter on plant than on a car
- Idling and low speed. Loaders, dozers and generators spend hours at low airflow with a hot exhaust.
- Dust settling on hot surfaces. Crop dust, coal dust and general site dust build up where it is hottest.
- Hydraulic and fuel lines routed close. A split line spraying onto a bare exhaust is the failure everyone on a site is trying to prevent.
- Confined engine bays. Heat accumulates with nowhere to go.
- People working alongside. A bare exhaust at working height is a burn risk before it is anything else.
When to use a blanket instead
Use lagging where the run is long, accessible and rarely disturbed. Use a blanket where the component is bulky, awkward or has to come apart for inspection.
Most fleets end up with both: lagging along the pipe and a removable exhaust or muffler blanket over the muffler and the manifold. For heat protection by industry, see our industrial and mining heat insulation page.
Fitting exhaust lagging
- Work on a cold exhaust. Always.
- Clean the pipe. Loose scale under lagging stays under lagging.
- Start at the cool end and work toward the heat, overlapping each turn by about a third.
- Pull it firm. Loose lagging moves, wears through and traps moisture.
- Fix with stainless steel tie straps at both ends and about every metre.
- Leave sensors, flexible joints and anything that has to move uncovered.
- Expect smoke and a smell on the first heat cycle. That is the binder curing.
Wear gloves and long sleeves. Fibreglass and basalt fibres irritate skin.
Exhaust lagging questions
How long does exhaust lagging last?
It depends on temperature, vibration and whether moisture gets underneath. Inspect it whenever you inspect the exhaust. Lagging that has gone hard, loose or oil-soaked has stopped working.
Can I lag an exhaust that leaks?
No. Fix the leak first. Lagging over a leak traps exhaust gas and moisture against the metal and accelerates corrosion, and it hides the leak while it does it.
What temperature does my exhaust actually reach?
Measure it rather than estimating, with an infrared thermometer at the hottest accessible point under normal load. Then pick the material with margin.
Is lagging the same as an exhaust blanket?
No. Lagging is fixed along the pipe. A blanket is a removable cover for one component. Large machines usually want both.
Tell us what you are running
Send the machine, the component and a photograph with a tape measure in shot. Call 1300 44 33 34 or email sales@koolwrap.com.au. We quote custom blankets from photos and dimensions and ship Australia-wide with tracking sent after dispatch.
