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Apr 3, 2022 · A 'breather membrane' is positioned on the outer side of the insulation, allowing vapour to escape from inside while repelling any water that tries to enter. A 'vapour control layer', positioned on the inner side of the insulation, reduces vapour transfer in a building.
Air and Vapour Control Membranes (AVCL, Vapour Control Layers, VCLs) play a crucial role in limiting the passage of moisture and air into the fabric of a building – ensuring the wellbeing of the occupants and providing longevity to the structure.
- What Is A Vapour Control Layer & How Do They Work?
- When Is A Vapour Control Layer needed?
- Vapour Control Layer Installation
- Vapour Control Layers FAQs
- Permagard – Damp Proofing Experts
A Vapour Control Layer, or VCL for short, is a plastic layer that restricts the movement of warm, moist air from inside a property into the fabric of the building. VCLs prevent excess moisture entering a wall’s cavity, behind the insulation. This reduces the risk of harmful interstitial condensation by ensuring that any moisture within the cavity i...
VCLs are a requirement in Building Regulations in certain new build situations. Existing properties might require a VCL if you are: 1. introducing internal stud walls and insulation 2. installing a new concrete floor with insulation 3. modifying the roof space Areas of high humidity would also need consideration.
Wall installation for vapour control layers
Generally speaking when you install a VCL to the walls of existing properties, you are installing a stud wall with insulation. 1. If you use permeable insulation material such as sheep’s wool, rockwool or fibreglass, the VCL is installed to the warm side of the insulation. The VCL is stapled to the timber studwork with the insulation wedged between the timber studs. 2. Any joints will need to be sealed with Single Sided Foil Tape. Remember, it is very important to seal everything and not just...
Installing a vapour control layer under a floor
A typical concrete floor build up that incorporates a VCL would be as follows: 1. Hardcore 2. Sand blinding 3. Damp Proof Membrane 4. Concrete Slab 5. Insulation 6. Vapour Control Layer 7. Screed Overlaps of the VCL membrane are sealed together with Double Sided Tape and the face of the joint sealed with Single Sided Foil Tape.
How to install a vapour control layer in a roof or loft
Interstitial condensation can occur in insulated lofts which have non-permeable roofing felt. This results in white fluffy mould on the underside of the roofing felt. Installing a VCL in your roof or loft space is a similar principle to the wall installation in that the VCL membrane is placed on the warm side of the insulation. Installations vary but usually the VCL is used in conjunction with breather membranes and ventilation systems when used in a roof space to encourage air flow.
What is the benefit of using a vapour control layer vs DPM?
When talking about floors, a vapour control layer is positioned at a different level to the damp proof membrane so generally you wouldn’t be able to substitute one for the other.
Can you use a DPM as Vapour barrier?
You can use a DPM sheet as a VCL and it will do the same job as long as it is sealed correctly and placed in the correct position – on the warm side of the insulation.
What’s the difference between a vapour control layer and a vapour control barrier?
Vapour Control Layers and vapour barriers are essentially the same thing. Some people and organisations will refer to the material that controls vapour movement as a VCL and some will call it a vapour barrier. It is important to remember that no material is completely vapour proof so the term ‘barrier’ can be slightly misleading. VCLs or vapour barriers will only reduce the vapour movement to an acceptable level. However, if the joints and perimeters are not sealed correctly, the VCL / vapour...
As experts in the field, Permagard are able to provide advice on VCL installation and troubleshooting. You can contact our expert team free of charge – they are always happy to share technical information and answer your questions.
An increasing number of experienced contractors are switching to a new best practice approach incorporating intelligent vapour control layers as a standard to protect buildings from structural damage. What makes these vapour control layers (VCLs) intelligent is that they adapt to changes in humidity conditions.
The selection and installation of a VCL, which has a high vapour diffusion in the winter and low resistance in the summer, can lead to a healthier building envelope. One membrane that is particularly suited to solid walls is Procheck Adapt.
Apr 3, 2022 · What is the purpose of a Vapour Control Layer (VCL)? When condensation occurs within a property’s structure, it may cause significant issues that are costly to rectify. VCLs play a key role in limiting the passage of moisture-rich air into the building fabric, safeguarding the structure.
People also ask
What is a VCL membrane?
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What is variable permeability (VCL)?
Nov 10, 2020 · A VCL in conjunction with the correct use of ventilation and membranes will effectively eliminate the risk of interstitial condensation. It’s the two design principles working together that minimise the damaging effects of condensation on the structure.
