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Insulation and Condensation: 5 Tips for Avoiding a Condensation Nightmare

Insulation and Condensation: 5 Tips for Avoiding a Condensation Nightmare

Is your insulation a condensation risk – potentially causing more trouble than it’s worth? Before you install cavity or roof insulation in your property, here’s a simple guide to building condensation, the risks and how you can avoid them.

Can Insulation Really Cause Condensation?

Imagine a glass of cold water on a hot day, typically coated with beads of condensation. Those condensed water droplets form when the humid, warm air touches the cold glass. Since cold air cannot hold as much moisture as warm air, the moisture is released when the air is chilled by the glass.

By the same principle, insulation can sometimes cause condensation. As insulation warms the inside of your building, the warm air holds more moisture and so the building’s interior becomes more humid. As the building cools each evening or during seasonal changes, the air also cools and releases moisture in the form of condensation.

But where does this condensation go? In a well ventilated building, condensation should quickly evaporate. But if the building is not properly ventilated (or if the building is particularly air-tight) moisture will condense into vulnerable areas of the building, including carpets, wallpaper, timbers… even clothes. You might start complaining of a “damp smell” and notice spots of mould.

Like the glass of cold water in our example, condensation can also form on the surface of insulation itself, especially in roof and wall cavities where the void on the exterior of the insulation is much colder than the insulated building. Over time, moisture can cause the insulation to degrade, rot, grow mould and lose its effectiveness.

Worst Case Scenarios

While the following problems are worst case scenarios, they do happen. Problems usually start small and go unnoticed, but over time will progress, requiring costly remedial works.

A multitude of condensation-related problems have been linked to insulation, including:

  • Black mould and fungus on walls, furniture and carpets
  • ‘Phantom Leaks’ where water seems to leak down walls for no reason
  • Peeling wallpaper and peeling, blistered paint
  • Rotted, decayed structural timber
  • Rust and corrosion of metal materials such as brick wall ties
  • Rising damp
  • Personal illness, including breathing and chest problems such as asthma

What’s more, the insulation causing the problems is rendered completely ineffective. Once it becomes wet, it starts to decay and loses its thermal properties. In fact, your building will most likely become colder than it was prior to insulation being installed.

5 Ways to Eliminate Condensation Risks

To avoid a condensation nightmare in your building, it is extremely important to buy the correct insulation products and make sure they are installed correctly. Here are five tips for peace of mind:

  1. Breathable vs Vapour Barrier? Install Insulation that is right for your climate. Depending on your climate, construction and conditions, breathable insulation may be preferable. On the other hand, vapour barriers are more suitable for hot and humid climates, in very general terms. Always consult your supplier or architect for more detailed advice on the right products for your project. There are new insulation products which allow water vapour to pass through them, stopping condensation from collecting on the surface. Known as “vapour permeable”, this new form of insulation significantly reduces condensation problems in climates where this is an issue. 
  2. Choose Ultra Thin Cavity Insulation. When insulating wall cavities such as double brick walls, it’s important not to completely fill the air cavity. Instead, choose an ultra-thin product that will occupy only a small portion of the cavity, allowing the all important air space to perform its intended duty of keeping walls separated and dry.
  3. Double-Check BCA Compliance. Be careful to choose insulation products that are compliant with the Building Code of Australia (BCA), which stipulates that cavity walls resist the passage of water from the outside wall to the inside wall. “Full-fill” insulation systems – including “blown in” style insulation – completely fill the wall cavity, providing a conductive bridge for moisture to travel through the cavity. This clearly conflicts with BCA requirements. Your best bet is, as mentioned above, to choose an ultra-thin cavity insulation solution.
  4. Planned Ventilation. Recent advances in building, window and door design have resulted in more air-tight buildings. While this is good from an energy conservation perspective, it is not good for eliminating condensation. To counteract the problem, talk to your builder about planning a whole-building ventilation system.
  5. DIY Ventilation. An easy DIY solution is use exhaust fans to reduce moisture inside your building. You can also open a window to allow fresh air inside. Cool air from outside holds little moisture. When it’s allowed inside, it will absorb a lot of moisture as it warms and reduce overall humidity levels, thereby reducing condensation.

Condensation is a very real risk that can cause major damage, but it is an avoidable problem. Making smart insulation choices before you build will prevent heartache down the track. Equipped with the knowledge in this article, be on the lookout for ultra-thin and vapour-permeable insulation products. A well insulated home or commercial property without the risk of condensation is possible – you just need to select the correct products.

About Kingspan Insulation

Kingspan Insulation is a market leading manufacturer of innovative ultra-thin flexible insulation products and super high performance rigid insulation products for building fabric and building services applications.