Wetness & Airtightness - What Makes an Adhesive Tape Stick and Stay Stuck - Part 2
In part one of this blog post we looked at the key characteristics of a robust airtight adhesive tape and the main features to look out for when comparing various adhesive tapes.
In this blog post we will delve a little deeper into one of the major benefits of what are known as 'solid acrylic' adhesives. We will discuss why these are particularly crucial for achieving long term airtight bonds especially in damper climates such as that experienced in the UK and Ireland.
Moisture: Where does it come from?
Although there has been a significant and marked increase in the number of off-site manufactured building units in recent years, for the most part, on-site bricks and mortar and lightweight open panel timber frame constructions are still the most common. This reinforces the case for dealing with the changeable and very often poor weather conditions during construction.
Usually, rain, atmospheric moisture and high humidity are inevitable during any construction project and this can often lead to moisture becoming trapped within the structure where, over time, it can cause issues with damp, mould and the formation of spores that will eventually lead to rot.
Moreover, while the UK’s wet climate is the main cause of moisture penetrating the structure during the build phase, it is not the only culprit. Moisture from plaster and screeds can also lead to high humidity during construction. This contributes to moisture-related structural damage and reduced service life of the property, as well as the impact that the presence of water can have on durability of an adhesive tape to remain stuck for the life time of the building.
Winter time adhesion
Higher humidity on site coupled with cooler surfaces leads to condensing moisture. An adhesive should possess sufficiently watertight properties to assure an airtight bond even in the event of an ingress of humidity (e.g. from plaster / screed)
The images above illustrate common winter time scenarios during a build with damp building components.
The use of inferior adhesive tapes to seal critical junctions in the airtight vapour control layer do not have the capacity to deal with such high moisture load stresses and thus lose their bond and fail.
Adhesive tapes have to be able to reliably withstand the challenges of moisture during installation as well as after they are installed. The first protective layer is the backing material that is used. A hard wearing polypropylene fleece backing, like that of Tescon Vana, is clearly more resistant to water than paper and capable of dealing with adverse weathering. However, moisture does not always come only from the outside, but often from the subsurface being taped to, for example damp timber elements. In this case, the advantage of this vapour permeable external protective layer is paramount, as the moisture can readily escape through the protective fleece and avoids build-up of moisture between the adhesive and the backing itself, which can bring about condensation issues.
As outlined in detail in the previous blog post, acrylate dispersion adhesives contain emulsifiers in their adhesive film after production. A characteristic of emulsifiers is that they store water, and they are still capable of doing this years later. If an acrylate dispersion adhesive comes into contact with water again, the adhesive re-emulsifies, often assumes a white colouring and can lose adhesive strength. Pure acrylates on the other hand are fully water-resistant, and as they do not react with water, their adhesive strength is preserved.
Dispersion glue tape (green)
|Dispersion glues when exposed to water, can cause glue to turn to a white lactic type soft gum that fails to remain adhered|
The need for airtightness tapes that can cope with high moisture levels as found on British and Irish sites should be stressed when specifying or considering appropriate airtight bonding elements. Solid acrylic glue provides the highest possible reliability in damp conditions, even underwater as illustrated on the video below. While this is not a standard application of an airtightness tape, it clearly illustrates the ability for solid acrylic glues to reliably function even under the most challenging conditions.
The seal itself, ensures that both the internal and external membranes can work to the maximum of their ability. These high performance, long-life, durable sealing tapes made from solid-based adhesives are manufactured by pro clima in Germany, who provide a complete airtight and windtight building system. Ecological Building Systems have distributed pro clima throughout the UK and Ireland for nearly two decades. To discuss your technical specification, CPD or training requirements on this exclusive range of tapes, membranes and sealing accessories, please contact us.
Written By: Fintan Wallace (Architectural Technologist) Ecological Building Systems