Description
Primary Pro 35mm x 19mm x 1m External Pipe Insulation
Primary Pro 35mm x 19mm External Pipe Insulation is a high‑performance, closed‑cell polyethylene insulation designed specifically for external heating pipework. With a 19mm insulation thickness and a weatherproof outer coating, it delivers reliable freeze protection, reduced heat loss, and long‑lasting durability in harsh outdoor conditions.
This insulation is engineered to resist water absorption, UV exposure, and mechanical impact. When correctly sealed using Primary Pro Bond & Seal, it forms a fully waterproof, vapour‑resistant system that maintains thermal efficiency and prevents moisture ingress.
Why Installers Choose This Insulation
- Primary Pro isn’t just pipe insulation, it’s a complete system to ensure best practice
- Closed‑cell polyethylene structure prevents moisture penetration
- Thermal conductivity of 0.035 W/mK @ 40°C for strong heat retention
- Water vapour diffusion resistance µ > 39,000 for long‑term performance
- UV‑resistant outer coating designed for external exposure
- Temperature range from –40°C to +105°C
- Fire classification D‑s1,d0 (EN ISO 11925‑2:2000)
- Fast, clean installation with easy‑cut foam
- Designed to work with Primary Pro Bond & Seal for a complete system
Other Key Features
- 19mm insulation thickness for dependable freeze protection
- Fits 35mm pipework (36mm x 21mm ±1mm tolerance)
- 1m length for modular installation
- Closed‑cell polyethylene insulation material
- Waterproof when correctly sealed with Bond & Seal
- UV‑resistant and weatherproof outer skin
- Reduces heat loss on external heating and hot water lines
- Suitable for copper, plastic, and steel pipework
- Ideal for harsh outdoor environments
Use Cases
- External boiler pipework
- Outdoor taps and garden plumbing
- Condensate pipes (freeze protection)
- Heat pump pipework
- Exposed hot water and heating lines
- Any outdoor run requiring waterproof, UV‑resistant insulation
Technical Specifications
| Material | Closed‑cell polyethylene insulation |
| Length | 1 metre |
| Pipe Compatibility | Fits 35mm pipework |
| Insulation Thickness | 19mm |
| Thermal Conductivity | 0.035 W/mK @ 40°C (BS EN 12667:2001, BS 5422:2009 Part 1) |
| Water Vapour Diffusion Resistance | µ > 39,000 |
| Water Absorption | Waterproof when sealed with Bond & Seal |
| Temperature Range | –40°C to +105°C |
| Reaction to Fire | D-s1,d0 (EN ISO 11925‑2:2000) |
| UV Resistance | Yes – use Primary Pro Maintenance Coat to recoat as needed |
| Suitable For | Copper, plastic, and steel pipes |
| Primary Pro Part Number | AS033 |
Frequently Asked Questions (FAQ’s)
How much bond and seal should you use?
We recommend using approximately 1/3 of a Primary Pro Bond & Seal tube per joint, to give a watertight seal and ensures the insulation cannot pull apart.
Is this insulation suitable for outdoor use?
Yes — it is designed specifically for external pipework and includes UV‑resistant, waterproof protection when joints are sealed with Bond & Seal.
What pipe size does this insulation fit?
This product is designed to fit 35mm pipes, with soldered or press fit connections. We also sell Primary Pro insulation for 22mm, 28mm and 42mm pipework.
Can I cut this insulation to size?
Yes — it cuts cleanly with a sharp knife and a mitre block for fast installation.
Why Primary Pro Performs Better Than Class O Insulation
| Performance Area | Primary Pro | Class O (Armacell) |
|---|---|---|
| Water Vapour Diffusion Resistance | µ > 39,000 (extremely high resistance to moisture) | µ ≥ 7,000 |
| Outdoor Suitability | Designed for external use with UV‑resistant, waterproof coating | Requires additional UV protection (paint or trunking) |
| Waterproofing | Fully waterproof when sealed with Bond & Seal | Absorbs water without additional protection |
| System Longevity | Coating can be recoated during annual service for extended life | UV degradation occurs unless protected |
| Domestic External Pipework Use | Specifically engineered for external domestic heating systems | Primarily designed for indoor HVAC and plant rooms |
| Installation on External Walls | Bond & Seal provides a complete weatherproof barrier | Requires additional sealing products |
