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Insulation and Damp Proofing

Insulation and damp proofing are two indispensable aspects of any residential or commercial building construction or renovation process. They are essential for enhancing energy efficiency, preventing structural damage, and creating a comfortable indoor environment. In this blog post, we will delve into both subjects and provide some practical tips for achieving effective insulation and damp proofing in your home.

What is insulation?

Insulation refers to materials or substances used to reduce the rate of heat transfer. By installing insulation, you can keep your building warm during the winter and cool during the summer, thereby reducing energy consumption and the associated costs. Apart from the thermal benefits, insulation also provides noise reduction and fire resistance.

There are several types of insulation available in the market. They include batts and rolls, blown-in insulation, spray foam insulation, and rigid foam insulation, among others. The choice depends on several factors including your building design, climate, energy-saving goals, and budget.

What is damp proofing?

Damp proofing is a series of methods and treatments used to prevent moisture from seeping into a building, whether through the walls, floor, or basement. The accumulation of moisture within a building can lead to several issues. These include mould growth, structural damage, and a decrease in thermal efficiency. It can also cause health problems for occupants due to increased allergens and poor air quality.

There are several types of dampness that can affect a building, and different types of dampness require different treatments. Here are the main ones:

  1. Rising Damp: This occurs when water from the ground rises up through the walls of a building due to capillary action. The water carries salts that can deteriorate plaster and paint, causing them to peel off.
  2. Penetrating Damp: This type of dampness is caused by water leaking through walls. It’s often a problem in older buildings with solid walls. It can also occur in buildings located in areas with severe weather conditions.
  3. Condensation: This is the most common type of dampness. It occurs when moist air comes into contact with a cold surface, such as a wall or window, causing water to be released onto that surface.
Rising damp
Rising damp

Damp proofing methods

Damp-proofing methods differ based on the type of dampness and the nature of the building. Here are a few commonly used methods:

  1. Damp Proof Course (DPC): This is a horizontal barrier inserted in the structure of a building, usually at the base level, to prevent rising dampness. The materials used for DPC include slate, bitumen, plastic or specially engineered bricks.
  2. Damp Proof Membrane (DPM): This is a membrane material applied to floors to prevent dampness from ground level from reaching the building. The material is usually a polymer formed into a flexible sheet.
  3. Cavity Wall Construction: This technique is used in the construction of new buildings to prevent penetrating dampness. The wall is constructed with a hollow space between two ‘skins’ of masonry, which prevents water from moving from the outer to the inner walls.
  4. Chemical Injection: In this method, a water-repellent chemical is injected into the walls to create a water-repelling layer, acting as a damp-proof course.
  5. Ventilation: Proper ventilation helps prevent condensation. This can be done through extractor fans in bathrooms and kitchens, or by maintaining an adequate air gap between insulation and the building structure.

It’s worth noting that damp proofing is best handled by professionals. They can diagnose the type of dampness affecting your property and recommend the most effective treatment.

Damp proof membrane on blockwork
Damp proof membrane on blockwork

Relationship between insulation and damp proofing

Understanding the relationship between insulation and damp proofing is crucial in ensuring the long-term health and comfort of your home or office building. Both insulation and damp proofing are protective measures, but their functions differ. Insulation primarily focuses on preventing heat transfer. Therefore, it keeps the interior of the building warm in winter and cool in summer. Damp proofing, on the other hand, aims to prevent moisture intrusion into the building.

When installed properly, both insulation and damp proofing work harmoniously to create an energy-efficient, healthy, and comfortable indoor environment. However, if not carefully planned and executed, the two can conflict. This leads to problems that might compromise the integrity and safety of the structure. Here’s how:

Moisture Trapped in Insulation

Poorly executed insulation can trap moisture, which then leads to dampness. This usually happens when a vapour barrier is incorrectly installed on the cooler side of an insulation layer.

When the warm, moist air from inside the building makes contact with the cooler insulation layer, condensation occurs, leading to dampness. The dampness can then cause multiple issues, such as mould growth, decreased insulation effectiveness, structural damage, and a potentially unhealthy indoor environment.

Insulation Affecting Damp Proof Course (DPC)

When installing insulation within a wall cavity, care must be taken not to bridge the damp-proof course or create a situation where moisture can bypass the DPC, leading to a risk of rising dampness.

In buildings where insulation is being retrofitted, an improperly installed insulation material could potentially disrupt an existing DPC or make it ineffective. This could, over time, lead to rising damp issues that could be quite costly to rectify.

XPS insulation and mosaic render can be used together to form a robust solution for insulation and damp proofing. Using XPS insulation below the Damp Proof Course (DPC) and finishing with a mosaic render system offers a combination of thermal resistance, water resistance, and aesthetics.

XPS, or extruded polystyrene, is a type of rigid foam insulation with a closed-cell structure. This type of insulation offers excellent water resistance and thermal performance. This makes it an ideal choice for use below ground level, where moisture exposure is inevitable.

The moisture-resistant properties of XPS allow it to prevent water ingress while its insulation characteristics help in limiting heat loss. When installed below the DPC, it provides a continuous insulation layer that bridges the thermal gap between the interior and exterior of a building.

A mosaic render is a type of decorative finish that’s usually used for external wall insulation systems. It involves applying small pieces (mosaics) of coloured glass, stone, or ceramics to create a decorative, durable, and weather-resistant finish.

Mosaic render isn’t just decorative. It also provides a robust, durable surface that can withstand weathering and wear, making it ideal for use in areas exposed to moisture or those that require additional protection.

  • XPS Insulation (1 board)

    From £8.50 Excl. VAT
  • Mosaic Render (EWI-050) – 25kg

    From £85.22 Excl. VAT
  • SALE Aquabase Bag
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    Aquabase (EWI-226) – 25kg

    £19.14 Excl. VAT£23.92 Excl. VAT
Thermal Bridging

Thermal bridging occurs when there is a significant difference in thermal resistance between the materials in a building. It’s essentially a “shortcut” for heat transfer, reducing the overall efficiency of the insulation. If damp proofing is not effectively integrated with insulation, thermal bridges can be created. This leads to condensation issues, mould growth, and a decrease in the building’s overall thermal performance.


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