"Can you just go over what's already there?"
Often yes. If it will act as a good base layer, we can often install over. A lot of homes have existing bulk-fill (batts) and loose-fill insulation (blow-in “fluff”) and while some of it holds up well, some of it turns into dusty nothing over time - especially old blown in cellulose. Check out this page for a deeper insight into ceiling insulation.
If it’s uneven, moisture-affected, or a mess to work around, we may suggest removal. We’re not big on charging you twice for the same outcome.
Glasswool vs Polyester (the straight answer)
We install two types of ceiling insulation:
Glasswool batts is the best value option. It’s proven, cost effective and available in high R-values.
Polyester blanket is the premium option. It’s durable, moisture resistant and performs consistently long-term (no settling/compaction).
But premium doesn’t always mean “best for your home”. Blanket products suit some situations perfectly and look mint - but in older or irregular ceilings, they can be awkward and involve too much cutting to justify the extra spend. This is especially the case when you have no existing insulation.
In these situations, we recommend a hybrid system: glasswool between joists + polyester blanket over the top. It’s a high performance result without wasting money.
We’ve got a page here where we provide deeper technical insights into glasswool vs. polyester as well as general considerations.
Why insulation installs fail
Ceiling insulation is seen often seen as DIY job. It can be — but only if it’s installed properly.
Performance drops fast when you’ve got leaks like:
• gaps between pieces
• insulation tucked/compressed
• missing sections around eaves
• clearances ignored around old downlights
• insulation moved aside and never put back
We install to NZS4246:2016 and best practice because these small details are the difference between “done by a weekend warrior” and “actually works”.