Vapour Tight Solutions for Solid Walls
Vapour tight systems are the most common solution used on the market today, usually in the form of thermal laminates – insulated plaster board
Considering a “non breathable” wall cannot cope naturally with the movement of water, then these 5 critical factors MUST to be present in an IWI system to make sure it’s “DESIGNED” performance is equal to it’s “INSTALLED” performance.
- Continuous Vapour Control Layer – Board Joints
- Continuous Insulation Layer – No thermal breaks
- Thermal Bridging due to multiply fixing
- Thermal Looping due an unventilated cavity
- Adequate treatment of thermal bridging – reveals, returns & floors
The key factor as the title suggests is, that the wall must be Vapour tight which simply means that the system you choose must stop hot vapour transferring from the warm side to the cold side of the insulation. Failure to address this key issue will lead to the hot vapour condensing on the cold wall and turning to water.
Over a period of time this will lead to the reduction in the performance of the insulation material but in addition the formation of mould and degradation of the fabric of the building will occur.
The second issue is that the insulation must be continuous and have no breaks. Studies have shown by the Fraunhofer Institute that, a 1mm gap in the insulation layer can lead in a drop in performance by a factor of 4.8. Therefore a system, designed to perform at 0.3 U Value, will in affect perform at 1.5 U Value.
Fixing multiple screws through the insulation layer either by a direct fixing method or screwing laminates onto timber battens is reducing the effectiveness of the insulation installed by creating a direct avenue for heat loss from the warm inside to the cold external wall.
If there is a cavity or air gap behind the thermal insulation system installed then this must be “unventilated” to keep this air warm and still. Failure to achieve this reduces the effectiveness of this air gap which is used to enhance U Value calculated values on the wall.
Failure to adequately deal with cold bridging at critical junction will increase the heat loss at this junction after the insulation has been installed which can lead to mould growth in these areas. A recent report published by the BRE states that heat loss at uninsulated junctions can be as high as 50% in certain cases.
At Enviroform Solutions we have addressed all of the above critical factors in the design of MagnaLine Slim complete with Magnablok to create a robust thermal laminate system.
“Off the shelf thermal laminates” will not achieve all of the above criteria due to their poor design and installation methods. The widespread use of these cost effective laminates?, coupled with the sectors lack of understanding of the effect, of not dealing with Cold Bridging contributes a large part of the “Performance Gap”.
STANDARD THERMAL LAMINATES EITHER FIXED ONTO BATTENS OR BY A “DOT & DAB” METHOD DO NOT FULFIL THE REQUIRED CRITERIA
Vapour Open Solutions for Breathable Walls
What is a breathable Material? If you are confused we don’t blame you. The term breathable is used loosely by various insulation companies and it means different things to different people.
In summary, to avoid confusion, for a material to be breathable it must have the following characteristics:
- Vapour Permeable – it has the ability to allow vapour pass through
- Hygroscopic – it has the ability to absorb moisture
- Capillarity Active – it has the ability to release absorbed water through its pores or capillaries
As we mentioned above if any of the materials used in the system don’t display ALL of the above properties they cannot be called “breathable” in the true sense of the term in relation to a wall.
Preparation before Commencing
As well as all the materials used in the system have to be breathable, all the component parts in the wall to be insulated must be as well. Therefore if you are insulating a wall then all materials like sand & cement, gypsum and paint must be stripped off to expose the original wall before preparation can start.
The first thing to do is to coat the wall with a minimum thickness of a 9mm lime parge coat to create a flat (very important), level, hygroscopic air tight inner later. Then and only then you can install your breathable system of choice.
In short the materials can deal with the formation of water due to vapour condensing and direct it in the direction of least resistance – either to the outside or inside face of the solid wall