The question that is the title of this study faces both the thermal insulation contractor and the investor of this project. When ordering a service, we hope that it will be done correctly, but in the words of Vladimir Ilyich Ulyanov, “Trust is good, but control is better.”
In the literature we can read: “The most common polystyrene installation system in Poland is the ETICS system (External Thermal Insulation Composite System), i.e. a composite insulation system for external building walls, previously known as the jointless thermal insulation system (BSO), and even earlier as the light-wet method” [1] .
The thermal insulation layer in this system is mounted with glue to the wall from the outside. The most commonly used method is the point method. Sometimes, especially in tall buildings, reinforced with mounting pins
However, the recommended solution, and in contrast to the point method, the correct solution is the perimeter-point method. This method is also called a frame with patches. In this solution, patches of glue are applied pointwise and an additional layer of glue is spread around the perimeter of the polystyrene, which is to ensure airtightness of the thermal insulation installation to the wall. After tearing off the polystyrene board, the glue should be on 40% of the surface of the polystyrene board.
The second way to implement this system is to glue the entire surface of the polystyrene. This method is called the comb method . It ensures complete tightness of the connection between the polystyrene and the wall. However, it involves greater glue consumption and can only be used on an even surface. The layer of glue is spread over the entire board using a comb trowel. It should be remembered that the information contained in the Technical Approval, the insulation project and the recommendations of the thermal insulation manufacturer should always be followed. Materials recommended by the manufacturer should be used. The use of an inappropriate binder can even damage the polystyrene.
Why a frame with panels? Why a frame? What about ventilation?
Many people, including insulation contractors themselves, ask themselves a question when they hear about gluing with a frame – why do we need it? After all, moisture must be removed from the polystyrene – there must be airflow, ventilation.
It is true that dampness of thermal insulation is an undesirable phenomenon. However, it can be avoided by designing the wall layers correctly. There is a general rule – materials with high diffusion resistance closer to the inside . Diffusion resistance is a property of a material that stops the free flow of water vapour through it. Properly selected materials reduce the pressure of water vapour, preventing it from condensing on the surface or inside the insulation layer. In such cases, there is no need to ventilate the polystyrene. Ventilation of polystyrene is only necessary in poorly designed and poorly made walls, and such should undoubtedly be avoided . It is worth asking the designer or contractor whether they have analysed the thermal and moisture properties inside the wall, whether they have met with a building physicist to discuss this topic. If not – we recommend that you make up for this deficiency. If they have ignored this topic – we advise you to look for a more reliable company.
Now that the issue of the necessity of ventilation has been resolved, it is worth answering – what will happen if we create a ventilation channel between the wall and the polystyrene ?
We will change the wall layering – greater energy losses
Each wall of a newly designed building must meet the requirements of the heat transfer coefficient U, as specified in the Technical Conditions. When selecting the thickness of the polystyrene, the designer almost always assumes that it will adhere tightly to the wall. This can be easily checked by verifying the coefficient calculated by him/her above. The lower it is, the lower the heat transfer through the wall, and therefore – lower energy losses and lower heating bills. In the case of a poorly ventilated gap, the U coefficient for a wall with the same thickness of thermal insulation is higher, which generates greater energy losses. In the case of a well-ventilated gap, the insulation layer is omitted in the calculations of the heat transfer coefficient U.
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To sum up: When we do not have a gap, the entire thickness of thermal insulation works. When we have a poorly ventilated gap – the insulation of the wall is reduced due to the size and arrangement of the ventilation holes – we need a greater thickness of thermal insulation to achieve the intended effect. When the gap is well ventilated – the insulation layer does not participate in reducing heat loss.
Fire safety
According to the Technical Conditions, walls must be made of non-flammable materials and must not spread fire. If there is a gap between the wall and the polystyrene that allows air movement, it may act as a chimney in the event of a fire. The temperature difference between the air heated by the fire and the cold, external air may cause a chimney draft effect, which will lead to the spread of fire between floors, and in extreme cases, the facade may come off and catch fire in neighbouring buildings.
The consequences probably do not need to be explained to anyone: neighbouring plots caught fire, people were burned, the fire department was in danger, and there were significant material losses.
Is my insulation done correctly? How can I check?
Therefore, let’s not underestimate the process of insulating our homes. Poorly executed thermal insulation means not only money spent that does not bring benefits, but also still high heating bills, thermal discomfort inside the building, and also – additional danger in a fire situation. Let’s not change our shelters into a cage full of traps!
Thermography comes to the rescue of errors in the execution of thermal insulation. By performing a thermography test with the appropriate interpretation , we can solve many problems related to the quality of use of our building.
[1] http://www.inzynierbudownictwa.pl/technika,materialy_i_technologie,artykul,system_etics,6409
