In the world of building materials, few things make as much difference to comfort, compliance, and energy efficiency as insulation. And yet, not all insulation is created equal.
Whether you’re lining a roof space, fitting out a commercial ceiling grid, or managing acoustic separation in a multi-res build, the choice between glasswool or polyester insulation can have a serious impact on performance, cost, and installation.
At Westgyp, we work with builders across WA who use insulation every day—from residential carpenters in Bunbury to large-scale fit-out contractors in Perth’s CBD. So, in this article, we’re breaking down how these three materials compare, what each one does best, and when to use one over the other.
Glasswool Insulation: The Industry Workhorse
When most people picture insulation, they’re thinking of glasswool (fibreglass)—and for good reason. It’s one of the most widely used materials in Australia thanks to its balance of performance, cost, and versatility.
What it is:
Glasswool is made by spinning molten glass into fine fibres, then binding them together to form soft, flexible batts or rolls.
Why tradies like it:
- Excellent thermal and acoustic performance for its price point
- Lightweight and easy to install in both new builds and retrofits
- Non-combustible and compliant with NCC fire safety requirements
- Available in a wide range of R-values and acoustic densities
Applications:
- Residential and commercial ceilings
- Wall and floor cavities
- Acoustic partitions and theatre rooms
- Roof spaces and underfloors
WA Example:
In Baldivis, a local builder recently used Ecowool glasswool insulation (supplied by Westgyp) for a two-storey coastal home. The clients wanted a cooler upper level and quieter bedrooms. The builder installed R4.1 thermal batts in the ceiling and acoustic-grade glasswool batts in the internal walls. The result? A cooler home in summer, reduced echo, and a noticeably quieter living environment—all with a single, cost-effective product family.
Best for:
- General-purpose thermal and acoustic insulation
- Projects needing NCC-compliant, fire-safe insulation
- Builders who want a proven, reliable all-rounder
Polyester Insulation: Clean, Safe, and Low-Allergen
Polyester insulation has gained popularity in recent years—especially among builders who work in residential renovations or schools, where handling safety is a priority.
What it is:
Made from recycled plastic (like PET bottles), polyester insulation, like FibreFlex, is a synthetic fibre product similar to what you’d find in bedding or clothing—only denser.
Why builders use it:
- Non-irritant—no itch, no gloves required
- Low allergen and dust-free, ideal for schools, hospitals, and homes with asthma concerns
- Resilient to moisture—holds shape even in humid or damp conditions
- Fully recyclable at end of life
Applications:
- Internal wall and ceiling insulation in residential builds
- Refits where occupant sensitivity or health is a concern
- Acoustic upgrades where clean handling is key
Performance comparison:
While polyester insulation typically offers good thermal resistance (R2.0–R4.0), its acoustic performance is slightly lower than high-density glasswool. It also has a lower fire resistance, which limits its use in certain commercial or multi-storey applications.
WA Example:
A school fit-out in Joondalup uses FibreFlex polyester insulation in new classrooms due to allergy considerations and ease of installation during a live-site upgrade. The installers were able to cut and fit batts without PPE, avoiding downtime or contamination issues.
Best for:
- Sensitive environments (schools, hospitals, aged care)
- Builders prioritising safe, clean installation
- Ceilings and walls where moisture or health are considerations
Comparing Performance at a Glance
| Property | Glasswool | Polyester |
| Thermal Efficiency | ★★★★☆ | ★★★★☆ |
| Acoustic Performance | ★★★★☆ | ★★★☆☆ |
| Fire Resistance | ★★★★★ | ★★☆☆☆ |
| Handling Safety | ★★★☆☆ | ★★★★★ |
| Cost Efficiency | ★★★★★ | ★★★★☆ |
| Moisture Resistance | ★★★☆☆ | ★★★★☆ |
| Environmental Impact | ★★★★☆ (recycled glass) | ★★★★★ (recycled PET) |
Choosing the Right Material for the Right Job
Here’s how to decide which insulation suits your next project:
1. Residential Builds
For most WA homes, glasswool insulation like Ecowool remains the best all-round option. It offers great acoustic and thermal balance, NCC compliance, and affordability.
→ Ideal for roof spaces, internal walls, and between floors.
2. Commercial Fit-Outs
Commercial projects often require acoustic separation and fire compliance. Glasswool acoustic batts in partitions deliver optimal results.
→ Great for offices, apartments, and retail builds.
3. Health or Education Projects
For schools, childcare centres, and hospitals, polyester insulation is an excellent choice for its low allergen and no-itch handling.
→ Perfect for retrofits and live-site upgrades.
4. Acoustic-Specific Spaces
For theatres, music studios, or shared walls, go for high-density glasswool acoustic batts. They deliver superior sound absorption and help achieve STC-rated partitions.
Natural vs Synthetic: The Eco Perspective
Both glasswool and polyester offer sustainability benefits, but in different ways:
- Glasswool (like Ecowool) uses up to 80% recycled glass and natural binders for a low-carbon manufacturing process.
- Polyester repurposes recycled plastic bottles into long-lasting fibre, keeping waste out of landfill.
For eco-conscious builders, glasswool offers the best balance between recycled content, performance, and energy efficiency—especially in NCC-compliant homes.
Handling and Installation Tips
For tradies and installers, ease of handling often decides what gets specified.
- Glasswool: Wear long sleeves and a mask for large installs, though modern binders (like in Ecowool) significantly reduce itch and dust.
- Polyester: Cut with shears or a utility knife—clean, safe, and perfect for quick retrofits.
Pro Tip: Always check the NCC Volume 2 and AS/NZS 4859.1 compliance markings on packaging—especially for energy efficiency credits and acoustic certification.
Cost Comparison (Typical WA Market Range)
| Material | Typical R4.0 Ceiling Cost (per m²) | Notes |
| Glasswool | $8 – $12 | Best value all-rounder |
| Polyester | $10 – $15 | Slightly higher, but cleaner handling |
Prices vary by project size and supplier, but these ranges reflect general WA trade rates for batts and rolls.
The Westgyp Recommendation
If you’re looking for a compliant, efficient and cost-effective insulation system for WA conditions:
- Use Ecowool glasswool insulation as your mainstay—it’s NCC compliant, fire safe, and delivers strong thermal and acoustic performance for residential and light commercial builds.
- Use Polyester insulation where health and handling safety are priorities.
This approach keeps things simple, consistent, and compliant across projects of all sizes.
Which insulation material is best?
Every insulation material has its place. The key is understanding where each one performs best.
- Glasswool (fibreglass): Reliable all-rounder—thermal, acoustic, compliant, and cost-effective.
- Polyester: Safe, clean, and sustainable—ideal for health-sensitive projects.
At the end of the day, the best insulation is the one that fits your project goals, compliance requirements, and budget—and with Westgyp’s range of glasswool and polyester solutions, you can build with confidence knowing you’re getting proven performance for WA conditions.