PU Insulation in SIP - Things you might not know..

When people talk about “low‑carbon insulation”, they often assume natural materials automatically win. But GWP (Global Warming Potential) doesn’t work that way. The numbers depend on how the material is made, not whether it’s petrochemical or natural.

GWP matters because it tells you how strongly a material contributes to global warming compared to CO₂, and it’s the key metric used in EPDs, F‑gas rules, and whole‑life‑carbon assessments. For PU, GWP is especially important because the blowing agent can swing the climate impact dramatically — older foams used high‑GWP gases, while modern 4th‑generation HFOs (like ours) have ultra‑low GWP, making the product compliant, future‑proof, and environmentally acceptable. In short, GWP is the number that shows whether a material is climate‑safe, legally compliant, and suitable for low‑carbon construction.

And here’s the part most people don’t realise:

Modern PU can have a lower GWP than many mineral wool and natural insulation products — especially when HFO blowing agents are used.

1. PU’s GWP is mainly determined by the blowing agent

• PU polymer itself isn’t the issue.

• The blowing agent creates the foam cells — that’s where GWP comes from.

• Modern blowing agents are low‑ or zero‑GWP.

  
  

2. HFO‑blown PU is extremely low‑GWP

• GWP < 1

• Zero Ozone Depletion Potential

• This puts PU in the same GWP range as natural materials.

  
  

3. Rockwool isn’t zero‑GWP

Rockwool is made by melting basalt at ~1500°C. That requires:

• very high heat

• significant energy input

• typically fossil‑fuel‑derived energy

  
  

So although Rockwool is “natural”, the manufacturing energy gives it a non‑trivial embodied carbon.

4. Natural materials aren’t automatically low‑GWP either

Wood fibre, hemp etc. can have:

• low embodied carbon

• but higher λ‑values, meaning thicker walls, = thicker foundations

• more timber, more fixings, more transport

• and higher operational energy over the building’s life

  
  

5. PU’s thermal efficiency changes the whole equation

This means:

• PU walls can be 30–60% thinner

• Less material overall

• Lower heating demand for decades

  
  

Operational carbon savings often exceed the embodied carbon of the PU itself.

6. PU SIPs are airtight

This is where PU quietly wins:

• No slumping

• No voids

• No thermal bypass

• The U‑value you design is the U‑value you get

Conclusion:-

• PU’s GWP today is very low, especially with HFO blowing agents.

• Rockwool and natural materials have embodied carbon from manufacturing and transport that people often overlook.

• PU’s superior thermal performance means lower heating demand for the building’s entire life — a major carbon saving.

• PU SIPs deliver predictable, airtight, stable performance.

When you look at whole‑life carbon, PU SIPs deliver a sustainable low energy building, thats more cost effect for the user.

www.sipit.uk info@sipit.uk T: 01224 531947