Seven Common Insulation Selection Mistakes Seen on Site

A mistake in insulation selection does not end with wasted money. The wrong material means lost thermal performance, equipment damage, fire risk and even failing handover inspection. Here are the seven mistakes we see most often in 30 years on site.

Mistake 1: selecting hot plant on ambient figures

Catalogue thermal conductivity (λ) is normally quoted at ambient temperature (25°C). Selecting insulation for pipework above 300°C on an ambient λ value leaves you with far less performance in operation. Glasswool 32K has a λ of 0.036 at 25°C, but 0.075 at 200°C — more than double.

Mistake 2: using glasswool above 350°C

Glasswool's maximum service temperature is about 350°C, yet it is sometimes installed on steam lines and hot plant above that. Beyond 350°C the glass fiber shrinks and melts, the form collapses and the insulating function is lost. From 350 to 600°C, mineral wool must be used.

Mistake 3: under-specifying the Cerakwool grade

Choosing the 1100°C grade for plant actually running at 1050°C. A product classified at 1100°C has a recommended continuous service temperature of about 950°C, and running continuously at 1050°C causes shrinkage. Always choose a grade above the actual operating temperature.

Mistake 4: not verifying the fire rating

Non-combustible or semi-non-combustible material is legally required in fire compartments, escape routes and external wall insulation. Using EPS or standard urethane foam because it is cheaper means failing handover inspection, or legal liability if a fire occurs. Always check the accredited certificate.

Mistake 5: omitting the vapour barrier on cryogenic lines

On LNG and liquid nitrogen lines, moisture from the ambient air penetrates the insulation and freezes, and performance collapses. The insulation is often installed with the vapour barrier omitted. Cryogenic pipework must be sealed completely, including every joint.

Mistake 6: leaving valves and flanges uninsulated

Straight pipe runs are insulated while valves, flanges and pumps are skipped on the grounds that they need inspection. The heat loss from a single valve can equal several metres of straight pipe. A removable insulation jacket gives you both inspection access and thermal performance.

Mistake 7: leaving damaged facing unrepaired

When aluminum or PVC facing is torn, or joints have opened, the insulation inside is exposed to moisture and contamination. Wet insulation can lose 30–50% or more of its performance. Inspect the facing visually every six months and repair damage immediately with aluminum tape.

Checklist

• ✅ Check the λ value at operating temperature, not at ambient
• ✅ Glasswool below 350°C only — above that, mineral wool or Cerakwool
• ✅ Specify Cerakwool one grade above the actual temperature
• ✅ Verify non-combustible certificates in fire compartments and external walls
• ✅ Cryogenic lines need a vapour barrier and fully sealed joints
• ✅ Fit insulation jackets to valves and flanges
• ✅ Inspect facing regularly and repair damage immediately