In the quiet corners of our homes, a silent intruder often goes unnoticed until it’s too late—mould. This insidious problem can find its way into or even be indirectly caused by insulation, which is one of the most critical components of an energy efficient home. So does mould actually grow on insulation? What are the health risks you should be aware of and how can mould on insulation be avoided?
What Exactly is Mould?
Mould (or ‘mold’ in American-English) refers to a type of fungus that grows in multicellular filaments called hyphae. Moulds, like fungi, have a vital job in nature – they break down things like dead plants or animals, keeping the environment balanced. There are over 100,000 different types of mould!
In households, mould often appears as fuzzy, discoloured patches on surfaces such as walls, ceilings or food. It reproduces through microscopic spores that can be airborne and easily spread. While some moulds are harmless, others can produce mycotoxins that may have adverse effects on human health, particularly for those with respiratory conditions or allergies.
If Insulation Gets Wet Will Mould Grow?
Wet insulation is definitely a recipe for mould growth.
From our experience, wet insulation is almost always caused by one or more of the following:
- While in storage. If the storage area (e.g. warehouse, transport depot, garage or carport) is prone to flooding, the insulation should be stored at least 10cm above the floor or ground.
- During transport. It’s not uncommon to see bags of insulation on the back of a ute or on an open trailer. If the load is not covered properly and rain comes unexpectedly, the insulation risks getting wet.
- Installation stage. Insulation installers will often push back a few roof tiles to provide access and airflow. It is critical that the exterior roof is completely sealed up after the job.
- Home renovations or extensions. Walls or ceilings will often be left exposed to the weather during home renovations or extensions. A responsible tradesman will cover a partial roof extension with a heavy tarp to keep out the rain.
- Water leaks. The two most common causes of water leaks are burst pipes and broken roof tiles. Over time, older roof tiles will also become susceptible to leaking due to the porous nature of cement. Check your roof periodically for signs of damage or leaks, especially after a large hail storm.
Signs Mould is Growing on Your Insulation
The two most obvious signs that mould is growing on your insulation is if there are unusual dark spots or patches on the insulation material and/or there is a musty or unpleasant smell in your house. When mould is growing, it might first look green with white edges before it turns black.
But, as a homeowner you’ll rarely find reason to climb up into your roof space or go under the house, so what are some other clues to indicate that your insulation might have a mould problem?
- Peeling or bubbling of the ceiling or walls
- Visible mould growth on the ceiling or walls
- Persistent respiratory issues, allergic reactions, headaches or worsened asthma for those living in the house.
Does Mould Cause Damage to Buildings?
Over time, serious mould can lead to structural damage and compromise the strength of structural timber, plasterboard and other common building materials. It can even grow inside HVAC systems, spreading harmful mould spores throughout the house. The presence of mould is certain to make the house less attractive in the real estate market.
Short and Long-Term Health Risks of Mould
Being exposed to mould can come with both short and long-term health risks.
Short-term exposure to mould can potentially lead to:
- runny or blocked nose
- sore throat
- skin irritation
- wheezing
- coughing
- sneezing
- itchy eyes
- headaches
- asthma attacks (if you have asthma).
If you have been exposed to mould for longer, or you are very sensitive to it, you may experience some of the following:
- fatigue
- sinus infections
- developing a mould allergy
- development of asthma (in children)
- severe mould infections like hypersensitivity pneumonitis (rare)
- organ damage
- legionnaire’s disease.
While most people won’t experience serious health problems from mould, those who do should contact a doctor.
Is There a Mould-Resistant Insulation?
Unfortunately, no insulation material is entirely mould-resistant. If insulation is sitting in a dark, warm space and gets soaked, it’s almost inevitable that it mould will form, even if it’s labelled as ‘moisture-resistant’ or ‘breathable’.
How Wet Can Insulation Get?
Perhaps your insulation has gotten a bit wet and now you’re questioning whether hundreds or thousands of dollars have gone down the drain. Here’s how you know if that’s the case.
If the insulation is so soaked that it will not be able to dry within a few hours in the sun, it’s probably damaged for good.
From our experience, water-damaged insulation is often wet only at one end of the bag. In cases such as these, our insulation contractors will simply cut away and discard the wet material. Never install wet insulation – if in doubt, dry it out.
Why Does Surface Mould Keep Coming Back?
While disinfectants are very effective for removing surface mould, they do not address the underlying issue causing mould growth.
Surface mould will keep coming back if the main cause (e.g. a leak or poor ventilation) isn’t fixed. So, it’s essential to find and fix the moisture source and ensure thorough mould removal. For this, you will need to book in a mould removal service.
How to Prevent Mould Growth on Insulation
- Ensure proper ventilation. Good airflow helps in maintaining optimal moisture levels. NSW Health advises people to turn on the exhaust fan when showering, cooking or doing laundry and have windows open on dry days, where possible. Ensure that your roof space and underfloor areas have adequate ventilation to prevent stagnant air and moisture buildup.
- Install vapour barriers. Australia is a humid country, so installing vapour barriers can help reduce moisture and prevent it from reaching the insulation.
- Maintain proper indoor humidity. Keep indoor humidity levels between 30-50%. Use dehumidifiers, if necessary, especially in damp or humid weather. Don’t overpopulate your living spaces with plants as these can increase humidity.
- Promptly address water damage. If your home experiences water damage, address it immediately. Remove and replace insulation that is water-damaged to prevent mould growth.
- Properly seal gaps and cracks. Seal gaps and cracks to minimise the risk of moisture entering the insulated space.
- Consider professional inspection. If you suspect there may be an issue with the insulation (e.g. after a storm), it’s best to arrange an insulation inspection.
FAQs About Mould and INsulation
Is the black stuff on my insulation mould? And is it dangerous?
If there are black, splotchy patches on your insulation, then yes, it’s probably black mould. Although not considered ‘deadly’ for the average person, mould on insulation can trigger cold-like symptoms (e.g. headaches, runny nose) or worsen existing health issues (e.g. asthma).
If insulation gets wet will mould grow?
Yes, insulation that has become wet (e.g. from a significant roof leak) is the perfect place for mould to grow. The insulation R-value is also reduced significantly.
Does insulation stop mould?
If mould is growing on e.g. the timber joists in a ceiling, the insulation will not stop that spread of mould. Mould growth is often related to moisture issues, and if mould is already present on timber joists, it suggests a pre-existing moisture problem that needs to be fixed.
Can wall insulation also get wet?
It’s quite unlikely wall insulation will get wet because it’s completely sealed in. However, water pipes do often run through walls, and in the case of a burst or leaking pipe, you could end up with wet and mouldy wall insulation. You’ll likely see mould growing on the surface of the wall and may also notice a musty odour.
Should mouldy insulation be removed?
Yes, soaked or mouldy insulation should most definitely be removed if you want your insulation to work optimally. Ineffective insulation may lead to poor temperature regulation, reduced comfort (e.g. bedroom being freezing although the heating is on) and higher energy bills.