How to Avoid Over-Insulating Your Home

When it comes to insulation, more isn’t always better — especially if it’s not installed correctly or without considering ventilation. While proper insulation is essential for thermal comfort and energy savings, over-insulating can lead to poor airflow, trapped moisture, and even mould.

In this blog, we’ll explore how to avoid over-insulating, how much insulation your Perth home actually needs, and how to strike the right balance between thermal performance and breathability.

What Does “Over-Insulating” Really Mean?

Over-insulating doesn’t mean installing too many batts — it usually refers to sealing a home too tightly without allowing for proper ventilation.

This can trap moisture, reduce indoor air quality, and in some cases, create condensation build-up in ceilings or walls. It’s not about how much insulation you install — it’s about how well it works with your home’s design.

1. Understand Your Climate Zone

Before choosing insulation, it’s important to know what R-values are recommended for your area. In Western Australia, Perth falls under Climate Zone 5 (Warm Temperate), which calls for:

• Ceiling insulation: R6.0 to R7.0 — like Earthwool R7.0 Batts
• Wall insulation: R2.5 to R2.7 — such as Earthwool R2.7 HD
• Underfloor insulation: R2.0 to R2.5 — like Earthwool Floorshield

Sticking within these R-value guidelines ensures your insulation is doing its job without restricting your home’s natural ability to “breathe.”

2. Don't Block Ventilation Paths

Ventilation is key. If you install thick layers of insulation without maintaining airflow (particularly in roof spaces), moisture from inside your home can become trapped.

Here’s how to avoid it:

• Leave roof vents unobstructed when installing ceiling insulation.
• Make sure eaves and soffit vents are still functional after adding insulation.
• Don’t pack insulation too tightly; compression reduces performance and restricts airflow.

3. Use the Right Insulation in the Right Place

Using the wrong type of insulation for the application can cause more harm than good. For example:

• Don’t install bulk batts in areas prone to condensation without proper vapour barriers or breathable foil (like Ametalin SilverSark).
• Use foil-faced boards like EcoTherm in applications where radiant heat needs to be reflected, such as under metal roofs or behind wall linings.

4. Upgrade Old Insulation Instead of Doubling Up

It’s tempting to lay new insulation over old layers — but if your existing insulation is degraded, damp, or pest-damaged, it could cause air blockages or create uneven thermal performance.

Instead, consider a full insulation upgrade using newer materials with higher thermal ratings and less bulk.

5. Work With Your Building Envelope, Not Against It

A well-insulated home should work as a system. That means pairing quality insulation with proper:

• Roof ventilation
• Window glazing
• Air sealing (with breathable membranes, not complete airtightness)

Think of it as finding the sweet spot — maximum insulation value without compromising your home’s ability to manage internal humidity and airflow.

Need Help? Let’s Get It Right

At Perth Insulation Centre, we specialise in helping WA homeowners find insulation solutions that balance performance with practicality. Whether you’re building new or upgrading existing insulation, we’ll help you choose the right R-value and materials for your home — and avoid overdoing it.

Have questions? Call us today on 0417 910 326 or explore our full range of Earthwool and foilboard insulation solutions.

Insulate smart. Breathe easy. Live better.