December 1, 2025

Green Goo in Electrical Wiring: What It Is, Why It Happens, and What NZ Homeowners Should Do

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If you live in a home built between the late 1960s and mid-1980s, you may encounter a strange problem: green goo oozing from power outlets, lights witches, or cable ends.

This sticky, oily substance is more than just unpleasant, it's a sign that the old PVC wiring in your home is breaking down.

Below is everything New Zealand homeowners need to know.

What is the Green Goo?

PVC wiring replaced black rubber cabling in the late 1960s. Rubber cable was notorious for failing quickly, its insulation degraded rapidly, exposing copper and creating fire and shock hazards.

PVC was a major improvement. However, the early blends of PVC used from the late 1960s through to the mid-1980s had a chemical flaw. Over time, the insulation in these cables began to break down, and one of the most visible symptoms is the green goo. The Green Goo itself is a mixture of plasticiser (the gooey, oily, sticky substance), and copper chloride (which gives it the green colour)

The insulation of the cable itself breaks down chemically, allowing the goo to work its way out of the cable, and out of outlets, switches and circuit protective devices. Manufacturers revised PVC formulations in the mid-1980s, and modern TPS cabling (1990s–today) no longer suffers from this issue.

Why Does it Happen?‍

‍Green goo appears due to a combination of factors:‍

1. PVC formulations of that era were poor

Cables manufactured in the 60s and 70s used early plasticiser formulations that were later found to migrate out of the cable.

2. Chemical reaction with copper

The oils created by the plasticiser dissolve compounds in the copper, creating the green colour.

3. Heat & humidity accelerates the breakdown

Hot roof spaces and wall cavities speed up plasticiser migration. As electricians, we often get callouts for these issues in SUMMER once the weather warms up, especially if the days have been humid as well.

Is the Green Goo Dangerous?
Chemically / Health-Wise:

The green goo itself is non-toxic in normal household-level exposure.

It's mostly plasticiser and copper compounds, which do not present any health risk.

The goo has a very distinctive smell though,  which can permeate the home environment.

It’s also very difficult to remove from fittings, and anything that comes into contact with it (fingers included!)

Electrically

The goo itself is not conductive, in most cases it won’t cause electrical shorting or shock risk.

However:

It’s the insulation breakdown that is the real concern.

Potential problems include:

  • Brittle insulation that cracks when moved
  • Weakened conductor insulation risking faults
  • Terminations (connection points) slipping due to lubrication
  • Ingress into fittings(especially power outlets) causing poor plug connections, which can result in overheating or failure
  • Corrosion/weakening of the copper conductors, creating a fire risk.
Where Is It Most Commonly Found in NZ Homes?

Green Goo style PVC Cable is typically found in homes built between 1965–1985. Cables which run through roof spaces - where heat accelerates degradation - tend to be the first circuits to present the green goo. In multi-storey properties, homeowners will normally see the green goo on the upper floors first for the above reason. It’s also common to see it in garages and workshops where cable runs are long,  andthe area is exposed to temperature cycling

You’ll often see the goo coming out of:

  • Power outlets and light switches(ooze behind faceplates)
  • Light fittings and junction boxes
  • Circuit protective devices in(or on) the switchboard.
What Should I Do if I See Green Goo?
The Best Option

By far the best long term solution is fully re-wiring the property with modern TPS cabling, especially if the issue is widespread and green goo can be seen in multiple locations.

With a full re-wire you’ll have peace of mind that your home is completely safe,

Re-wiring eliminates any electrical risk associated with cable breakdown.

Localised Repairs

If the issue is localised to a few outlets and switches, or a single circuit, and the other cabling in the home looks to be in good condition/are undisturbed, then localised repairs can be an acceptable solution.

This is obviously a lower cost solution,however it does mean that additional repairs and re-wiring will likely be required in years to come.

If your budget is tight, rewiring the worst affected circuits first is better than doing nothing at all, and will drastically improve the safety of your home.

Outlet and Fitting Replacement

For both full re-wires and localised repairs, we recommend replacing any fitting that has come into contact with the green goo.

Usually this will mean that switches, power outlets and light fittings are replaced along with the affected cabling.

What About Electrical Certification?

For an electrician to sign off an installation, the electrical equipment must be in good condition and fit for continued service.

If wiring insulation is degraded, sticky,brittle, or leaking, it fails this requirement and it’s unlikely the electrician will sign this off as safe.

An electrical certificate cannot be legitimately issued on work that leaves unsafe wiring in place.

What About Insurance & Building Compliance?

Insurance assessors know about green goo and may require rewiring before issuing or renewing a policy.

Pre-purchase building inspectors regularly record green goo as a hazard o their inspection reports, which can become a hurdle / barrier for prospective purchasers.

In property sales, we’ve seen this issue used by buyers to negotiate a lower price.

Summary

Green goo is a sign that old PVC wiring from the 1965–1985 era is breaking down. While the goo itself isn’t toxic or conductive, the insulation failure behind it is a genuine electrical hazard,which can lead to overheating, faults, and fire risk. The safest solution is a full rewire using modern TPS cable. Localised repairs may be acceptable for minor issues but are not a permanent fix.

If you spot green goo in your home, get in touch with the team at The Conduction Company, One of our friendly, qualified electricians and inspectors will stop by, assess the extent of the damage, and advise on the most appropriate repair strategy.

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