If your home has been around for a few decades, chances are its ceiling cavity contains blown-in insulation—a common retrofit method in mid-to-late 20th century New Zealand homes.
While it served a purpose at the time, old blown-in insulation can degrade, shift, or absorb moisture over time, leaving homeowners wondering: should I remove it?
The answer depends on a few critical factors, which we’ll break down here.
What Is Blown-In Insulation?
Blown-in insulation refers to loose-fill material—often cellulose (recycled paper), fibreglass, or mineral wool—that is mechanically blown into a ceiling cavity using a hose. It’s designed to blanket the area without seams or gaps, and was widely used due to its speed and affordability.
In newer homes or professionally maintained retrofits, it can still be effective. But older installations often deteriorate or underperform due to compaction, moisture exposure, or poor original application.
When Should You Consider Removing It?
While not all old insulation needs to be replaced, there are several signs that it’s time to reassess:
1. It’s No Longer Performing
Over time, blown-in insulation can settle, compressing under its own weight or being displaced by drafts, rodents, or even foot traffic during roof access. Compacted insulation loses thermal resistance—meaning your home is harder to heat or cool, and you may see a rise in energy bills.
2. It Has Been Contaminated
If insulation has been exposed to:
- Rodent droppings or urine
- Bird nests or carcasses
- Smoke damage or soot from a fire
- Asbestos from surrounding ceiling materials
…it’s no longer safe. Contaminated insulation can pose serious health risks and should be removed by professionals with appropriate safety measures in place.
3. It’s Damp or Mouldy
Cellulose insulation is particularly vulnerable to moisture. Leaky roofing or condensation can soak insulation over time. Wet insulation not only loses effectiveness but can contribute to mould growth, timber damage, and indoor air quality issues.
Any insulation that has become damp—especially if it has remained wet for more than 48 hours—should be professionally removed and replaced.
4. You’re Planning a Top-Up or Upgrade
In some cases, it’s possible to top up old blown-in insulation with modern materials like glasswool or polyester blankets. However, this only works if the existing insulation is dry, clean, and evenly distributed. If the old layer is patchy or degraded, it may be more effective to remove it entirely and start fresh—especially to meet modern R-value standards.
What Are the Benefits of Removing and Replacing?
- Improved Thermal Performance: Upgrading to high R-value insulation like R4.0–R6.0 can significantly reduce heat loss.
- Healthier Home Environment: Eliminating mould, dust, or contaminants improves air quality.
- Increased Home Value: Well-insulated homes are more attractive to buyers and renters, and meet current Healthy Homes or Building Code requirements.
- Future-Proofing: New materials like 100% polyester offer superior durability, fire safety, and environmental performance.
How Does the Removal Process Work?
At Premier Insulation, we carry out insulation removals with care and precision. The process typically includes:
- Assessment – We inspect the condition of your existing insulation and determine whether full removal is required.
- Extraction – Using high-powered vacuum systems, we safely remove blown-in insulation without disturbing ceiling linings.
- Clean-Up – The cavity is cleared of debris, contaminants, and loose materials.
- Installation of New Insulation – We install fresh insulation (glasswool or polyester) with full coverage and compliance to NZ Building Code standards.
All materials removed are disposed of responsibly, and we document the process for Healthy Homes or renovation records.
So—Should You Remove It?
If your old blown-in insulation is contaminated, water-damaged, or underperforming, removal is not only wise—it’s necessary. Even if it appears intact, an assessment may reveal that replacement would yield much better thermal and energy results in the long run.
At Premier Insulation, we’ll give you honest, evidence-based advice on whether your current insulation should be removed, topped up, or left as-is. Your comfort, health, and compliance are our priority.
Book a free insulation assessment today and find out if your ceiling is working as hard as it should be.