Insulation Thickness Selection Guide
Insulation Thickness Selection Guide
How to Choose the Right Thickness for Pipe Insulation — HVAC, Chilled Water & Refrigeration
Choosing the correct insulation thickness is critical for preventing condensation, maintaining energy efficiency, and ensuring long-term system performance. This guide helps HVAC installers, mechanical engineers, and contractors select the right thickness for every application.
📐 Quick Reference Table
| Application | Pipe Temperature | Recommended Thickness | Material |
|---|---|---|---|
| Domestic Hot Water | 60-80°C | 13 mm | PE or Elastomeric |
| Domestic Cold Water | 5-15°C | 13 mm | Elastomeric (closed-cell) |
| HVAC Heating | 40-80°C | 13-19 mm | Elastomeric or Mineral Wool |
| Chilled Water (HVAC) | 6-12°C | 19-25 mm | Elastomeric (closed-cell) |
| Refrigeration Lines | -30 to +10°C | 19-32 mm | Elastomeric (closed-cell) |
| Heat Pump Lines | -10 to +65°C | 13-19 mm | Elastomeric |
| High-Temperature Steam | 100-150°C | 25-50 mm | Mineral Wool (K-Rock) |
🎯 Key Principles
1. Lower Temperature = Thicker Insulation
The colder the pipe, the more insulation you need to prevent condensation. Chilled water and refrigeration lines require significantly thicker insulation than hot water pipes.
2. Closed-Cell Material is Essential for Cold Applications
For any pipe below ambient temperature, you MUST use closed-cell elastomeric insulation (like K-FLEX ST or SK). Open-cell materials will absorb moisture and fail.
3. Consider Ambient Conditions
High humidity environments (plant rooms, basements, coastal areas) require thicker insulation to prevent surface condensation.
4. Comply with Building Regulations
Part L of the Building Regulations specifies minimum insulation thicknesses for energy efficiency. Always check current requirements for your project.
🧪 Condensation Prevention
The golden rule: The outer surface of the insulation must stay above the dew point temperature to prevent condensation.
Example:
Chilled water pipe at 6°C in a plant room at 20°C with 60% relative humidity:
- Dew point = approximately 12°C
- Insulation surface must stay above 12°C
- Recommended thickness: 19-25 mm of closed-cell elastomeric
🔧 Installation Tips
- Seal all joints properly — Use K-FLEX 800 adhesive or self-seal (SK) products to prevent vapour ingress
- Insulate valves and fittings — Don't leave gaps at elbows, tees, or valves
- Protect outdoor insulation — Use UV-resistant cladding or Solar HT grade for external pipework
- Allow for expansion — Don't compress insulation during installation
📊 When to Go Thicker
Consider increasing thickness beyond the standard recommendation when:
- Pipes run through high-humidity areas (basements, plant rooms)
- Ambient temperature is very high (summer conditions)
- Pipe temperature is at the lower end of the range
- Energy efficiency is a priority (commercial buildings, Part L compliance)
- Long pipe runs where heat loss/gain is significant
🛒 Shop by Thickness
📚 Related Guides
- Dew Point & Condensation Explained
- Elastomeric vs Mineral Wool — Which Is Best?
- Pipe Bore Size Chart
- Back to Knowledge Centre
Need help choosing? Contact our technical team for project-specific advice.