The Importance of Vapour Control Layers



Why are Vapour Control Layers so important?

Mitigating the risk of Condensation within a building’s structure is an extremely important step to consider when building or roofing a property. Just a little condensation can quickly turn into a very expensive problem to fix and can rapidly worsen if left untouched, so it’s worth it to invest time and money ahead and prevent this damage from happening. One way to protect your building and reduce the chance of damage is by using a Vapour Control Layer, or VCL. Here is everything you need to know about VCLs, why they are so important and how multifoil insulation can be used in the prevention of condensation.

Tlx silver multifoil insulationWhat makes a good Vapour Control Layer?

A Vapour Control Layer is a layer of material that keeps warm, moist air from moving into the fabric of the building from the interior. It usually goes behind or below the insulation and keeps any nearby moisture at a manageable level. Small amounts of vapour will evaporate without any problem thanks to the porous nature of bricks. A vapour barrier can be made from all sorts of materials, but there are some options that work better than others. The effectiveness of the material can be measured in terms of a permeability rating, or how easily moisture and vapour can pass through each substance. Materials like polyethylene, aluminum foil, polyamide film, and latex vapour barrier paints all have very low permeability ratings, meaning they are the most effective.

Where to install a Vapour Control Layer

When you put insulation into a building’s walls or roof, you make a cold space between the insulation and the outer structure where interstitial condensation can build up. To prevent this, you put your VCL behind the insulation, preventing any warm air that makes it through from getting into that cold space.

Vapour Control Layers in walls:

Our multifoil insulation is a 2-in-1 insulating vapour control layer and can be secured to the inner face of the stud with the insulation fitted between the studs. Next you will need to seal joints with single sided foil tape. It’s extremely important to seal everything completely, not just sections of the TLX Silver. Whatever you use, make sure that ceiling joints, floor joints, and any vertical joints where your VCL meets adjoining walls are properly sealed. Once you are sure that everything has been sealed correctly, you can screw plasterboard to the studs and finish the wall. You’ll want to be extra careful about the joint between the bottom of the plasterboard and the seal.

Vapour Control Layers in roofs:

Installing a Vapour Control Layer in a roof or loft space is very similar to how you would install it in a wall. multifoil insulation can be secured to the underside of the rafter with 38x38mm battens set crosswise to minimize thermal bridging. Any additional insulation is then secured in-between the rafters. Leaving an unventilated air gap between the topside of the TLX Silver and the underside of rigid insulation will create a layer of warm unventilated air and will contribute to the insulation build-up as static air is a good insulator. A breathable membrane above the rigid board to encourage air flow.

A Vapour Control Layer is a step you can’t skip

Vapour damage, like all water damage, is a serious problem you don’t want to find yourself up against. By introducing a simple vapour control layer, you can protect yourself from the stress and cost associated with this kind of damage. This is why it is incredibly important to make sure that all of your building project’s insulation is backed up by a high quality and trustworthy Vapour Control Layer that can handle any moisture threatening to damage your hard work.

Preventing condensation using multifoil insulation

We understand mitigating the risk of condensation can be a demanding task. Therefore, with over 20 years of experience in the field of multifoil insulation, we are well placed to help. Our Silver and Gold multifoil insulation perform very different jobs within the structure of a building but each have distinct properties to effectively reduce condensation risk whilst saving on space.

1. Working from the inside: Opting for TLX Silver is a great space saving solution since it performs 2 jobs in 1; it is an excellent vapour barrier, but it also contributes to the thermal energy saving of the building  with its shiny heat reflective surfaces.

2. Working from the outside: If you are working from the outside using Gold installed above the rafters, an additional Vapour Control Layer below the rafter is not necessary. This is due to the following:

3. An insulating vapour barrier is extremely breathable.

4. This allows water vapour to pass straight through it and into the tile space above.

5. Is fitted above the rafters

tlx gold insulating breather membraneSince Gold occupies the coldest part of the temperature profile, its shiny breathable undersurface keeps the static air beneath it warm enough to prevent a dewpoint occurring, therefore minimizing the risk of condensation. 

Multifoil insulation is the perfect thickness for optimum performance but also completely airtight to minimize the risk of condensation building up inside of your roof or wall. TLX Silver and TLX Gold can also be used alongside additional insulation in order to achieve extremely low U values. They are BBA certified and have LABC Approved Solutions,  giving peace of mind that they are trusted. Our multifoil insulation is used in many different roofing projects like loft conversions, flat roofs, new builds, pitched roofs, barn conversions, and more.

Further reading on this subject can be found HERE

Our case studies demonstrating these principles in practice can be found HERE

vapour control technical advice