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What To Do With Wet Insulation?

If you’ve had a leaking roof or some sort of water intrusion in your home, you may find yourself dealing with the rather unpleasant task of having to address wet insulation. This is a pressing issue that should not be ignored. Wet insulation can not only compromise the thermal efficiency of your home but also pose serious health risks due to mould and mildew.

How to identify wet insulation

Often, homeowners might first notice something amiss when they see dampness or water spots appearing on their walls or ceilings. These spots could start off as small discolourations but could grow over time, indicating that water is accumulating in the area. It’s vital to investigate these spots immediately. Their presence often suggests that insulation in the wall or attic may be affected.

Another telltale sign is an unusual musty smell that permeates the area. While our first instinct might be to dismiss it or cover it up with air fresheners, a musty smell can be a clear indicator of underlying moisture problems. Moisture trapped in insulation provides an ideal breeding ground for mould and mildew, which could be the source of the odour. Ignoring this smell can lead to more extensive damage over time and could also pose health risks.

Physical deformities in the wallboard can also provide crucial clues. If you observe swelling, sagging, or warping in your walls or ceilings, this could very well signify that the insulation behind them has absorbed a significant amount of water. In this case, it’s essential to act quickly and assess the insulation to prevent further structural damage and health risks associated with mould and mildew.

Last but not least, visible mould or mildew on the walls, ceilings, or even on exposed insulation in your attic should set off immediate alarm bells. Mould and mildew not only deteriorate the insulating material but also present serious health hazards, especially for those with allergies or respiratory conditions.

Types of insulation and their water-repellence

Mineral wool, Expanded Polystyrene (EPS), and Kingspan K5 are all types of insulation materials that are known for their water-resistant or hydrophobic properties to some extent. However, it’s important to understand that “water-resistant” does not necessarily mean “waterproof”. Each of these materials has its own limitations when it comes to moisture exposure.

Mineral Wool

Mineral wool is often considered to be water-repellent rather than waterproof. It does not readily absorb water and will wick moisture away. However, if it is exposed to a large amount of water for an extended period, it may become saturated and lose its insulative properties. Once it becomes wet, mineral wool can be difficult to dry out completely, potentially leading to mould and mildew issues.

Expanded Polystyrene (EPS)

EPS is more water-resistant than mineral wool and is often used in applications where moisture is a concern. However, if it is exposed to water for an extended period, it can absorb some moisture, leading to a reduction in its thermal performance. It’s worth noting that while EPS may absorb less water than other types of insulation, it’s still not entirely waterproof.

Kingspan K5

Kingspan K5 is a type of phenolic foam board that has good water resistance due to its closed-cell structure. However, it’s not completely impervious to water. Prolonged exposure to moisture can cause the material to degrade over time, reducing its effectiveness as an insulator.

General guidelines
  1. Installation: Ensure that these materials are correctly installed with proper sealing to minimise the risk of water intrusion.
  2. Protective layers: Using additional water-resistant or waterproof layers in the construction can further protect these materials from getting wet.
  3. Inspection: Regular inspections are advised to check for any signs of water damage, especially after severe weather conditions.

Assess the damage

Once you’ve identified that you’re dealing with wet insulation, it’s essential to evaluate the extent of the damage. To do this, you may need to access hard-to-reach areas like attics, crawl spaces, or even inside the walls. Before beginning your assessment, make sure you’re properly equipped with the necessary safety gear. Masks help to avoid inhaling harmful substances like mould spores, gloves to protect your hands, and eye protection for additional safety.

Your objective during this assessment is not just to gauge how much of the insulation is wet but also to check the surrounding materials for damage. This could mean looking for warped wood, corroded pipes, or compromised electrical wiring, as these could have been affected by the moisture as well. In the case of mineral wool, which can hold a large amount of water, you may also find that the weight of the wet insulation has caused sagging or even collapse in parts of your ceiling or walls.

A moisture meter can also be a useful tool to quantitatively measure the level of moisture in different materials. This would offer a more precise idea of the extent of the problem.

Determine the cause

Figuring out the root cause of the moisture issue is absolutely crucial, not only to address the current problem but also to prevent similar issues in the future. Water can infiltrate your home in various ways. For instance, a leaking roof would primarily affect the insulation in your attic, while bursts or leaking pipes could lead to wet insulation in your walls or floors.

In some cases, the problem may be more insidious, such as poor ventilation leading to condensation within wall cavities, thereby wetting the insulation over time. Sometimes, it could be a faulty moisture barrier or improper installation of the insulation itself that has led to the issue. Extreme weather events like floods could necessitate a broader scope of inspection and repair.

A detailed inspection of the exterior of the home can also be instructive. Look for damaged roofing materials, blocked or broken gutters, and cracks in external walls. These could be potential avenues for water ingress. Identifying the cause may sometimes require the expertise of professionals.

Determining the cause is not just a matter of fixing the immediate problem but should be seen as a proactive step in preventing future incidents. Once you’ve pinpointed the issue, corrective measures must be taken promptly to mitigate it. This can include roof repair, plumbing fixes, or improving home ventilation.

Removing the wet insulation

  1. Isolate the area: The first step is to isolate the affected area. This prevents the spread of mould spores or other contaminants. This can be achieved by hanging heavy-duty plastic sheets around the area.
  2. Removal process: When dealing with smaller affected areas, you might be tempted to just remove the visibly wet sections. However, water can spread quickly through insulation material. Therefore, it’s often advisable to remove a slightly larger area to ensure all wet material is taken out. Use a standard utility knife to carefully cut out the insulation without compressing it.
  3. Bagging and disposal: Place the wet insulation material in heavy-duty rubbish bags. Seal the bags tightly. Also, consult local waste disposal guidelines to ensure you’re disposing of the material in a compliant manner.

Drying the area

  1. Ventilation: Open up windows and use fans to bring fresh air into the area, which aids in the drying process.
  2. Dehumidifiers: For a quicker and more thorough drying, consider using a dehumidifier. This is particularly useful in areas like attics and basements where natural ventilation might be limited.
  3. Inspect the structure: While the area is exposed, check for other damages, such as warped wood or corroded wiring.
  4. Small areas: If only a small area is affected and the insulation is minimally wet, some types of insulation like mineral wool can sometimes dry out on their own without mould growth, especially if the cause of the wetness is promptly resolved. However, this is a bit of a gamble and generally not advisable due to the potential for hidden mould growth.

Replacing the wet insulation

  1. Material selection: If you found that the existing insulation material was inadequate or contributed to the moisture problem, consider switching to a more water-resistant material.
  2. Install moisture barriers: Before installing new insulation, make sure to install or replace moisture barriers like vapour barriers or vapour retarders as needed. This step is crucial to prevent future moisture problems.
  3. Small areas: If only a small area was affected, you could perform a “patch job”. Simply cut a piece of new insulation to fit the exact area where the old insulation was removed. However, ensure that the new insulation is tightly fitted against the existing material to avoid thermal bridges. Cold bridges compromise the insulation’s effectiveness.
  4. Professional installation: While DIY is an option, insulation is tricky to install correctly. Mistakes can lead to gaps, compression, or other issues that compromise its effectiveness. Professional installation can often offer a more secure, and long-lasting solution.

Storage of insulation on site

Whilst mineral wool, EPS, and Kingspan K5 all have varying degrees of water-repellence, proper storage on-site is still essential. Much like your basecoat and adhesive bags, insulation boards should be protected from the elements as best as possible. Most insulation boards come in packs that are shrink-wrapped. However, this does not constitute sufficient protection for the most part. Therefore, internal storage or temporary sheltering is advisable.


8 thoughts on “What To Do With Wet Insulation?

  1. Can the way the insulation is stored be a cause of water damage? I’m about to have some delivered and worried with the rain at the moment.

    1. Hi Wendy, that can certainly cause some water damage. If you don’t store your insulation internally or elevated above the ground, it can be affected by any rain that accumulates and pools.

        1. EPS won’t get wet, but something like Mineral Wool will need to be allowed to dry out. The timeframe for that naturally depends on the conditions but covering it to prevent further saturation is crucial.

    1. Hi Bruce, the problem you may encounter is that you’ll need a thicker board to achieve the same U-value as the K5 achieves. If you use the same thickness of EPS as K5 to keep the thickness uniform, you’ll create an area that’s not as well insulated (cold bridge). So ideally, you’ll need to replace with K5 and try to keep the dry throughout the process. If you’re unsure, drop us an email on marketing@ewistore.co.uk and we’ll put you in touch with our Technical Team.

    1. Hi Henry, something like indirect fired heaters or electric fan heaters work. These don’t introduce any moisture into the air.

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