Kingspan Therma vs Kooltherm Range — What’s the Real Difference?

If you’re specifying insulation or planning an energy upgrade, you’ve probably come across two familiar Kingspan names: Therma and Kooltherm. Both are high-performance rigid boards from the same manufacturer, but they differ in core material, thermal performance, fire behaviour, moisture resistance, and cost.

For context, both belong to the wider Kingspan product family, but they are engineered for different performance requirements.

1. Core Material and Why It Matters

Therma products use PIR (polyisocyanurate) rigid foam, while Kooltherm uses phenolic foam. Phenolic foam generally achieves a lower thermal conductivity than PIR, meaning:

• Kooltherm delivers better performance in a thinner board.
• Therma offers very good performance but may require slightly greater thickness.

Both use foil facings and contain no fibre, but the different foam chemistry drives their performance characteristics.

2. Thermal Performance: Lambda Values and Thickness

Thermal conductivity (λ-value) is the key metric when comparing insulation:

• Therma PIR: typically 0.022–0.027 W/m·K
• Kooltherm phenolic: typically 0.019–0.021 W/m·K

In practical terms:

• Kooltherm allows you to hit the same U-value at a reduced thickness — ideal for tight retrofits or limited build-up depth.
• Therma still performs well, but usually needs slightly more thickness to match Kooltherm’s insulation level.

In some applications — such as cavity walls — the difference in required thickness can be significant.

3. Moisture Resistance and Long-Term Stability

Both insulation types are closed-cell foams, meaning they resist water ingress when properly installed. Their foil facings and cell structure help reduce vapour diffusion.

• Therma (PIR) — moisture-resistant, foil-faced, suitable for most construction types.
• Kooltherm (phenolic) — very fine closed-cell structure, strong moisture resistance, excellent dimensional stability.

Both perform reliably when correctly installed with appropriate membranes and vapour control layers.

4. Fire Performance

Fire performance depends on the exact board, not the range as a whole. Each product has its own certified reaction-to-fire classification.

Some Kooltherm products achieve higher fire ratings in specific applications, while various Therma PIR boards also meet required standards for many typical uses.

Always:

• Check the Euroclass rating of the specific board.
• Confirm that it applies to your installation type — roof, cavity, soffit, pipework, wall lining, etc.

5. Handling, Installation, and Typical Use Cases

Therma (PIR)

• Common in walls, floors, pitched roofs, and flat roofs.
• Easy to cut and handle.
• Generally more affordable.
• A solid choice where space isn’t tight.

Kooltherm (Phenolic)

• Used when premium performance or minimal thickness is required.
• Ideal for retrofits or high-spec new builds.
• Common in cavity boards, soffits, internal linings, and pipe insulation.
• Delivers maximum performance per millimetre.

6. Cost Considerations

Kooltherm typically costs more per m² due to its higher thermal performance.

However, thinner boards can save space, reduce fixing lengths, and improve design efficiency — offsetting costs in some projects.

Therma PIR remains the cost-effective choice when build-up depth is available and value is the priority.

You can find different thicknesses such as 100mm Kingspan and 50mm Kingspan depending on your specification requirements.

7. Choosing the Right Product: A Quick Guide

• Limited space? Choose Kooltherm for maximum performance in minimal depth.
• Working to a budget? Therma provides excellent value where thickness is less critical.
• Fire performance considerations? Always check the specific board’s Euroclass rating.
• Moisture-prone build-ups? Review vapour resistance and consider membranes.

Kingspan Therma and Kooltherm are both reliable, high-quality insulation ranges, each suited to different project priorities.

Therma offers strong performance and cost-effectiveness using PIR foam, while Kooltherm provides superior thermal conductivity in thinner profiles thanks to phenolic technology.

Your best choice depends on: target U-value, available space, fire rating requirements, and budget.