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Airtightness
When it comes to insulation, airtightness is a crucial factor that should not be overlooked. Airtightness refers to the ability of a building envelope to prevent the uncontrolled flow of air in and out of a structure. By effectively sealing any gaps or cracks, airtightness ensures that the desired indoor temperature is maintained, energy efficiency is optimised and potential moisture and condensation issues are minimised.
At Insulation Merchant, we understand the significance of airtightness in insulation, which is why we offer a wide range of airtightness membranes, tapes and other associated materials. These products are specifically designed to enhance the thermal performance of buildings and provide a secure sealing solution.
Our airtightness membranes are made from high-quality materials that offer exceptional durability and resistance to air leakage. These membranes are easy to install and can be applied to various surfaces, including walls, roofs and floors. By creating an airtight barrier, these membranes prevent heat loss and reduce energy consumption, resulting in lower heating and cooling costs for building owners.
In addition to airtightness membranes, we also provide a selection of airtightness tapes. These tapes are specially formulated to provide a strong and reliable seal for joints, corners and edges. They are flexible, easy to apply and offer excellent adhesion to a wide range of surfaces. Whether you're working on a new construction project or renovating an existing building, our airtightness tapes ensure that every connection is properly sealed, eliminating any potential air leakage points.
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Which membrane do I need? Breather Membrane vs Vapour Control Layer
These two products are often confused, but they serve opposite functions and go on opposite sides of your insulation. Choosing the wrong one — or fitting it on the wrong side — can trap moisture and cause serious long-term damage. If you are unsure, always follow the insulation manufacturer's specification and seek advice from a qualified professional.
| 🌬️ Breather Membrane External — cold side of insulation |
💧 Vapour Control Layer (VCL) Internal — warm side of insulation |
|---|---|
| What it does: Lets moisture vapour escape from the structure outwards while keeping wind and rain out. | What it does: Stops warm, moisture-laden air from the inside of the building from entering the insulation layer. |
| Where it goes: On the outside (cold side) of the insulation — typically under roof tiles, slates or cladding, or behind external render. | Where it goes: On the inside (warm side) of the insulation — typically fixed to rafters, studs or joists before plasterboard is fitted. |
| Typical applications: Pitched roofs, timber frame walls, green roofs, and ventilated façades. | Typical applications: Warm pitched roofs, internal wall linings, ground floors, and cold-roof conversions. |
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| Shop Breather Membranes → 65 products — for external use |
Shop Vapour Control Layers → 69 products — for internal use |
⚠️ Always follow manufacturer guidance. Membrane specifications vary by product, roof pitch, and building type. Where there is any doubt about the correct product or installation method for your project, consult the manufacturer's technical datasheet and seek advice from a qualified building professional before proceeding.