Damage Caused by Water and Moisture to Thermal Insulation

As you know, what is expected from thermal insulation material is that it fully performs the task of preventing cold and heat. For this, the material must remain dry under conditions of use. Because thermal insulation material that is exposed to excessive moisture, becomes wet, or absorbs water loses its thermal insulation properties partially or completely.

Therefore, the insulation material or insulation work must be thoroughly and well protected from moisture and water. Protection of the insulation work and material is achieved through appropriate plaster, paint or coating applied over it. Thermal insulation applied to buildings in the form of external cladding protects the building's inhabitants from the hot-cold effects of the external environment, and also maintains the building's walls and related systems at relatively constant temperatures throughout the year. This means that movements resulting from thermal changes in the building will be reduced to a minimum level. Nowadays, external thermal insulation application to buildings is becoming widespread at a rapid pace. However, during and after application, sufficient attention is not paid to measures to protect the thermal insulation. These include, in brief, architectural details, incorrect and inadequate materials, incorrect applications, incorrect techniques, inadequate surface preparation, incorrect or incomplete curing, poor and inadequate workmanship, and lack of supervision. The main subject of this article is the effects of water and moisture originating from the external environment, which can damage the thermal insulation material, the plaster, paint and coating on it. Even before five years pass since the building is constructed, we see errors and defects on the building's external surfaces, mostly caused by water and moisture, and we regard them as natural; we never question the underlying reality at all. In construction practices of the past, water and moisture would damage the plaster, paint and coating, creating undesirable appearances. However, nowadays, due to the application of thermal insulation materials in the form of external cladding on outer surfaces, we may face a much more serious situation, such as the loss of the insulation property of the insulation material due to water and moisture effects. Again, due to water-absorbing paint, plaster, or water-permeable thermal insulation material, we may lose the insulation board, plaster or coating completely from the building surface.

Water and Moisture from Interior Sources

The sources of water and moisture originating from inside the home are varied. Bathrooms and toilets, cooking food and washing dishes in the kitchen, activities such as laundry washing, and possible water leaks in the plumbing system all contribute to dampening the building. Additionally, people living in the home environment and plants present introduce additional moisture loads. If this is not controlled, the humidity level in the room's air, which should normally be around 40-50% for comfortable living, increases, and the ambient air becomes stuffy and uncomfortable. Excess vapor in the environment not only causes discomfort to people and affects their quality of life and comfort, but also creates a suitable environment for microorganisms in the home to reproduce more and faster. Additionally, it triggers mold formation on cold surfaces on the interior side of uninsulated walls. To remove or reduce excessive vapor in the building or to allow vapor to pass from the interior wall surface to the exterior, the surface (plaster, coating, paint, etc.) must be sufficiently vapor-permeable; however, it should not be forgotten that vapor passage through walls and the removal of water or vapor in this way is quite limited (around 1-2%). The reduction of vapor in the interior air should be achieved through ventilation. The air in the home should generally be changed every 2-3 hours; however, this change interval may vary depending on the number of occupants, the size of the home, the activities carried out, and the quality of the building.

Water and Moisture from External Environment

The wetting of buildings from the external environment occurs due to rainfall and snowfall. Additionally, condensation of moisture present in the external air on the cold external surface of the building should not be overlooked as a source of moisture gain. Although it is thought that snowfall does not stick to the wall and does not contribute to water absorption by the walls, in some cases snow that adheres to the wall can indeed be a source of water causing wall wetting and damaging effects. However, the main factor that wets the external surfaces of buildings and subsequently causes a chain of many negative effects is rainwater. If it did not rain or if rain fell in calm and windless weather without hitting the walls, the external surfaces of our buildings could remain unchanged and undamaged for many years, just as on the first day. We observe that rainwater falling to the ground in stormy weather accumulates and flows quickly, but we never think about what happens to the rainwater that hits buildings and wets their plaster and paint, changing their color. In reality, depending on the speed of the storm, raindrops can strike the walls at various angles. When raindrops come at a 45-degree angle, the amount of rain hitting the wall equals the amount falling to the ground.

Damaging Effects of Moisture and Water on Plaster and Building Physics

The plaster, paint and coatings on the external surfaces of buildings change over time due to the effects of external conditions compared to when they were applied. You may see that one day cracks, fine or deep, have appeared on the building surface, plaster has peeled off here and there and even in large chunks, paint color has changed, weathered and even disappeared, and if there is any coating, it has partially peeled off. When we carefully examine the damage listed here, we find that it ultimately has some connection with water. The plasters and paints that we think will protect the building walls, providing them with a smooth, good-looking and colorful shield, are fundamentally damaged and even lost after some time due to water-related reasons. Building external facades are restored to good condition through repairs to the plaster and reapplication of paint or coating. This renewal work requires some cost, more or less. However, the growing prevalence of external insulation (cladding) today requires much greater care in thermal insulation materials and systems, plasters and plaster systems, and workmanship. In other words, in addition to their previous tasks, plasters have taken on the additional duty of protecting the thermal insulation material and providing comfort conditions for us, creating energy savings and reducing fuel expenses.

For this reason, in the event that the insulation material is damaged somewhere and for some reason, whether there is a repair method or material for the damaged section should be questioned and investigated before the insulation decision is made.

Why? If an incorrect thermal insulation material and system are selected, the maintenance, repair or renewal costs can reach very high amounts that are difficult to bear. The factors causing plaster deterioration can be grouped into three main categories. Some of them appear immediately after the plaster mortar is applied. Others require a short period of time to pass. Some, from the beginning, subtly affect the plaster throughout its lifetime in a damaging, undesirable manner. The amount and rate of deterioration or aging varies depending on the conditions in which the plaster is located, the aggregate structure and type, and the cement.

These are:

1. Mechanical effects (Frost effects: surface capillary or wide cracks, texture loss, etc.), 2. Chemical effects (on plaster aggregate), 3. Chemical + mechanical effects (Aggregates that can react with cement can cause weathering and material loss from the surface). Many of the plasters that we assess as sound when new begin to deteriorate, crack, swell, and weather after a certain period of time. Plaster (sand + cement + lime + water and additives as needed) systems are generally hydraulic in nature, and hardening and reaction begin with water and continue to a certain extent depending on conditions. Water, which is an essential chemical at the beginning and during the hardening process, can later, in turn, cause many undesirable effects on the hardened mass.

These kinds of errors resulting from excessive water result in the final plaster having a porous and weak structure, and especially when proper curing and protection measures are not taken, surface capillary or deep cracks appear.

Excessive and unnecessary water and other workmanship-related errors thus lead to the creation of a weak and sponge-like plaster at the outset, which easily absorbs water. As explained here, plasters of varying sizes, shapes and widths, and arising from different causes, that are cracked, porous, absorbent and weak are highly susceptible to the harmful and damaging effects of water and moisture. They can absorb water like a sponge, and as a result, many negative consequences can arise. These are the damaging effects of acids produced by the combination of some gases in the air with water on the plaster. When CO2, SO2, SO3 and NOx gases present in the air combine with water or water vapor, weak and strong acids are formed that react with CaCO3 found in most materials used for plaster (sand, gravel, stone) and even wash them away. Similarly, the portions within the binder affected by acids and water gradually disappear over time, leaving voids of different sizes and shapes in their place. Thus, after a time, we are faced with plaster whose aggregate and binder are partially or largely washed away, and which is very different from its original condition and appearance, with a jagged surface and increased surface voids. In summary, it must not be forgotten that excessive water during any type of mortar preparation and application will make the work easier, but will fundamentally damage the system. Water that enters interior spaces through various routes from plaster and coatings that have not been correctly selected with appropriate material, have not been applied with good workmanship and proper technique, causes excessive moisture loads in interior spaces and such a situation triggers mold formation. Consequently, the emergence of mold-related problems is inevitable.  

How Should the Plaster on the External Surface of Building Walls Facing Outward Be?

• Water-repellent (hydrophobic) coating, plaster, paint or coating should be used, • For rapid removal of absorbed water, the coating, plaster, paint or coating should be sufficiently vapor-permeable. • To overcome the danger of frost events, plasters and paints with plastic properties should be preferred as well as those that are sufficiently elastic; however, it must not be forgotten that excessively flexible coatings will block vapor diffusion. • Mixtures of materials that are poorly soluble in water should be selected for the plaster aggregate, thereby reducing or preventing dissolution. • The binder of the plaster material should have water-repellent properties, and the binders should not react with the plaster aggregate. • Plasters and paints should be compatible with the surfaces to which they are applied and should behave similarly towards external conditions. • The use of lightweight aggregate in the plaster material should be considered and even preferred.

How Do Water and Moisture Affect Thermal Insulation? What Are the Solutions?

• Water and moisture alter and damage the physical properties of all types of thermal insulation materials to varying degrees, depending on the type of material. • Property changes occur as a result of physical effects and/or chemical reactions. • When the external walls of buildings are to be covered with external thermal insulation material, it should be preferred that the plaster and paint have water-proof properties. • Additionally, to ensure that both vapor originating from interior spaces and water and vapor entering from the external surface are expelled to the outside, it is essential to ensure that the thermal insulation material has adequate vapor-permeability. • The degree to which the plaster and paint surface is suitable for water retention (rough or smooth) affects the water absorption amount. This should be known and solutions should be provided accordingly. In low-rise houses, wide eaves can be quite effective in preventing rain from hitting the walls. • It should be preferred that the thermal insulation material has water-repellent properties. • Naturally, the adhesives used in attaching thermal insulation materials should also have water-repellent properties. Ali Germili - Technical Application Manager / Baumit