KNAUF VS ISOTHERM
INSULATION
Which One Actually Delivers the Best Results?
Choosing between Knauf Insulation and Isotherm Insulation is one of the most important decisions you’ll make when insulating your home.
Get it right — and you reduce your electricity bill, stabilise indoor temperatures, and improve comfort immediately.
Get it wrong — and you waste money while your house stays too hot in summer and too cold in winter.
This guide breaks down the real differences between Knauf and Isotherm insulation — based on performance, cost, durability, and real-world use in South African conditions.
Best Overall Performance: Knauf Insulation
Best Eco-Friendly Option: Isotherm Insulation
Best Value for Money: Knauf (long-term)
Best for Moisture Resistance: Isotherm
What is Knauf Insulation
Knauf Insulation is a high-performance glass wool insulation designed to trap air and reduce heat transfer.
It works by trapping millions of tiny air pockets, slowing down heat transfer through your ceiling.
Key Advantages:
- Excellent thermal resistance
- Non-combustible (very important for safety)
- Proven long-term durability
- Widely used in commercial and residential buildings
The Reality:
Knauf is built for performance first. It’s not the easiest to install, but it delivers where it matters — temperature control and energy savings.
What is Isotherm Insulation
Isotherm Insulation is a polyester-based insulation made from recycled plastic bottles.
It’s designed to be safe, user-friendly, and environmentally friendly.
Key Advantages:
- No-itch and easy to handle
- Made from recycled materials
- Dust-free and allergy-free
- Safer for DIY installation
The Reality:
Isotherm focuses on comfort and ease of use, rather than maximum performance.
SHOP Ceiling Insulation Products
- 145mm Isotherm m2 @ R123.56
- R-value @ 3.77
- Roll Dimensions 5m x 1.2m @ 6m2
- B/B 1/2 can Burn
- 135mm Knauf m² @ R112.12
- R-value @ 3.78
- Roll Dimensions 7.5m x 1.2m @ 9m2
- Non combustible
- 135mm Aerolite m2 @ R102.70
- R-value @ 3.78
- Roll Dimensions 5m x 1.2m @ 6m2
- Non Combustible
Knauf vs Isotherm Insulation – Full Comparison
Material Difference
- Knauf = Glass wool
- Isotherm = Polyester
This is the foundation of everything.
Glass wool traps air more efficiently → better insulation
Polyester is softer and safer → easier handling
Knauf vs Isotherm Insulation
Knauf vs Isotherm Insulation
Knauf vs Isotherm Insulation South Africa
Knauf vs Isotherm Insulation South Africa
Thermal Performance (Most Important Factor)
This is where the real difference shows.
- Higher thermal efficiency
- Better heat retention in winter
- Better heat blocking in summer
- Good performance
- Slightly less effective than glass wool
👉 If your goal is maximum energy savings, Knauf wins.
INSTALLATION DIFFERENCE
Knauf Insulation
- Requires gloves and mask
- Can irritate skin
- Professional install recommended
Isotherm Insulation
- No itching
- Easy to cut
- DIY friendly
- For DIY, Isotherm is easier in the Knauf vs Isotherm Insulation option.
👉 If you’re installing yourself, Isotherm has the advantage.
Knauf vs Isotherm Insulation SIDE-BY-SIDE COMPARISON TABLE
| Feature | Knauf Insulation | Isotherm Insulation |
|---|---|---|
| Material | Glass wool | Polyester |
| Thermal Performance | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐ |
| Fire Resistance | ⭐⭐⭐⭐⭐ | ⭐⭐⭐ |
| Moisture Resistance | ⭐⭐⭐ | ⭐⭐⭐ |
| Lifespan | 30+ years | 30 years |
| Installation | Requires PPE | Easy DIY |
| Eco-Friendly | High | High |
| Price | Competitive | Slightly higher |
Knauf vs Isotherm Insulation This Is What Matters
Fire Resistance (Critical Safety Factor)
This is non-negotiable.
- Knauf = Non-combustible (strong advantage)
- Isotherm = Fire retardant (but can burn & melt)
👉 For safety, especially in roof spaces:
Knauf is significantly more advanced and is regarded as the most advanced thermal insulation
Installation Differences
Knauf:
- Requires gloves and a mask
- Soft and smooth to the touch
- Better installed professionally
Isotherm:
- No itching
- Easy to cut
- Ideal for DIY
Both Knauf and Isotherm are ideal for DIY Installation. With Isotherm a little easier
Polyester Ceiling Insulation
- Isotherm Insulation is dust-free
- Isotherm is manufactured from PET plastic bottles
- Polyester is used in couches and duvets
- Do not compress Polyester for extended periods
👉 Polyester Ceiling Insulation is perfect for people with allergies.
Isotherm has an edge here
Price vs Value
Prices change, but generally:
Typical trend:
- Knauf = better cost-to-performance ratio
- Isotherm = slightly higher price for comfort + eco
👉 Don’t choose based on price alone — choose based on performance over time.
👉 The real question is not price — it’s performance vs convenience. Knauf Wins
Lifespan & Durability
If you want the best overall insulation performance → choose Knauf
If you want easy handling + moisture resistance → choose Isotherm
Knauf vs Isotherm for sure, Knauf Insulation wins
- Knauf = 30+ years
- Isotherm = 15–20 years
Knauf holds its structure better over time.
Which Insulation is Best for South African Homes?
South Africa has extreme temperature swings:
- Hot summers
- Cold winter nights
Most homes are under-insulated.
What you need:
- Strong heat resistance
- Long-term durability
- Reliable performance
👉 That’s why Knauf is often the better choice overall
Roof Insulation SA keeps a wide variety of Roof Insulation products for all types of applications.
Knauf vs Isotherm – Long-Term Cost Comparison
Most people look at price per roll — that’s a mistake.
You should be looking at:
- Energy savings
- Lifespan
- Performance consistency
Knauf:
- Lower energy bills
- Longer lifespan
- Better return on investment
Isotherm:
- Slightly higher upfront cost
- Easier install
- Lower performance long-term
👉 Over 10–15 years, Knauf usually works out cheaper.
When You Should Choose Knauf Insulation
Choose Knauf if:
- You want maximum thermal performance
- You are looking for maximum energy savings and comfort
- You want long-term savings
- Fire safety is important
👉 This is the best all-round option for most homes
When You Should Choose Isotherm Insulation
Choose Isotherm if:
- You want an easy DIY installation
- You prefer eco-friendly materials
- Allergy-free insulation
- You want a non-itch solution
👉 Best for allergies
Common Mistakes When Choosing Insulation
Most homeowners get this wrong.
- Choosing based on price only – Cheap insulation costs more in the long term
- Ignoring climate – Coastal vs inland matters
- Not installing correctly –Even the best insulation fails if installed badly
- Choosing comfort over performance – Easy handling doesn’t mean better insulation
Installation Matters More Than You Think
Even the best insulation won’t work if installed incorrectly.
You need:
- Full ceiling coverage
- No gaps
- Correct thickness
- Proper layout between trusses
👉 This is why professional installation often delivers better results
Final Verdict – Knauf vs Isotherm
Let’s be clear:
- If you want best performance → Knauf
- If you want easy handling → Isotherm
There is no “perfect” product — only the right choice for your situation.
👉 But for most homes:
Knauf is the stronger long-term investment
Get the Right Insulation Installed Properly
The product is only half the job — installation is the other half.
👉 Get expert advice
👉 Choose the right insulation
👉 Install it correctly the first time
FAQ Section
Which insulation is better, Knauf or Isotherm?
Knauf performs better thermally, while Isotherm is easier to install and more moisture resistant.
Is Isotherm insulation worth it?
Yes, especially for DIY installation and eco-friendly applications.
How long does Knauf insulation last?
Typically over 20 years when installed correctly.
Can I install Isotherm insulation myself?
Yes, it is designed for safe DIY installation.
Which insulation is best for Cape Town?
Knauf for performance, Isotherm for moisture resistance in coastal conditions.
ABOUT US
Our Journey began in 1993 in Durban, KZN. We have since moved our office to the beautiful Western Cape of South Africa, where the Roof Insulation company was born. This company has a burning passion for insulation and a clear vision to make a difference in energy efficiency. Ladies and gentlemen, let us introduce you to Roof Insulation Western Cape Pty Ltd.
SERVICES
- CEILING INSTALLATION
- INSULATION INSTALLATION
- ONLINE SHOP
AREAS WE COVER
- Cape Town
- Northern Suburbs
- Southern Suburbs
- Somerset West
- Hermanus
- Paarl
- Stellenbosch
- Worcester
- West Coast
- Langebaan
- Vrednburg
AREAS WE COVER
- MosselBay
- George
- Knysna
- Pletenberg Bay
- Johannesburg
- Pretoria
- Midrand
- KZN
- Midlans
- North Coast
- South Coast
