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The European Union has set the ambitious aim of reducing human greenhouse-gas emissions by 80-95% by 2050 in comparison to 1990. The EU is slowly moving towards nearly zero-efficiency buildings that in turn create a demand for building materials, as the energy costs of a building make up roughly 40% of total energy usage.

“It is clear that in order to contribute to reducing greenhouse gas emissions, the amount of energy used in a building for heating, cooling, water heating and lighting must be reduced, and renewable energy sources will probably need to be harnessed,”according to Kuldar Kongo, product manager of Krimelte OÜ, in responding to the Energy Performance of Buildings Directive.

All new buildings finished after 31 December 2020 must be nearly zero-energy buildings, according to the aforementioned directive. This requirement for new buildings used and owned by government offices has already been in effect since 2019.

According to Kongo, the energy efficiency of a building depends on the general need for energy, type of supplied energy, on-site production of energy from renewable energy sources, and the amount of heat loss through the outer envelope. “Various methods and solutions must be applied together to meet the requirements of a nearly zero-efficiency building, from the right planning of the buildings’placement and use of renewable energy sources to well thought-out envelopes to minimise heat loss. The construction of nearly zero-efficient buildings in Europe increases expectations and demands regarding the quality of materials and the competence of salespersons.”

The manufacturers of building materials have been focusing on the development of materials for the construction of nearly zero-energy buildings for years. “For example, the product portfolio of our trademark Penosil includes products that solve technical heat and moisture related issues, thereby contributing to better energy efficiency, and these features must also be kept in mind during any further product development. We have developed a complete solution for energy efficient window placement, by which our products help to solve problems and issues related to a window node. In addition to energy efficiency, the development of our products also considers their durability in time and the contribution to a healthy indoor climate.”

Heat loss through envelope

Increasing the thickness of the insulation layer on the outer envelope is sufficient to minimise heat loss. According to Kongo, it should not be forgotten that although heat loss by conduction through envelopes is one of the major factors influencing energy loss, a building will also lose heat in addition to heat conduction through unplanned air leaks and cold bridges. The insulation layer thickness has often reached its limits of cost effectiveness, meaning that no additions will be cost efficient and one should focus on the removal of air leaks and cold bridges.

“The importance of air tightness is illustrated by the fact that proofing subsequent to construction has become unavoidable”, Kongo adds. “The envelopes are accompanied by a large amount of other important requirements: avoidance of technical humidity issues, fulfilment of indoor climate requirements, reduction of noise issues and fire safety.”He adds that one of the major challenges regarding the buildings is correct window placement, because this involves interruption of the external insulation layer along with the airtight and water vapour proof layers.

How can you guarantee a correct and energy efficient window installation?

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Reduce heat losses to a minimum. Use materials for window joints with the least amount of heat conduction such as PU-building foam. In addition, the heat conduction losses depend on the depth of joints e.g., they are smaller for windows with wide frames due to the increased depth of a joint.

Provide air tightness to reduce heat loss due to air leaks. The correct application of quality montage foam should by itself be enough to provide air tightness in a joint. To guarantee air tightness during the buildings’operation, the additional use of special tapes, membranes or mastics should be considered.

The warranting of water vapour resistance protects structures against excessive moisture. Depending on the climatic conditions, the water vapour may move from indoors out or from the external environment inside. The first scenario is predominantly present in Nordic countries during most of the year while the second scenario is in mainly warmer areas. Specific air and vapour resistant tapes, membranes and mastics are used to avoid the entrance of water vapour into the envelope. Such a construction must always include a high quality thought-through ventilation solution.

Ensure the escape of moisture trapped within the construction. This includes moisture in construction details during the construction or moisture ending up in the envelope due to poor quality in planning or building. Humidity must not be trapped in the construction - in such cases, tapes with little vapour resistance or self-expanding sealants are used.

Protect inner construction from external weather conditions (UV radiation, precipitation, wind). This presumes that the joint is covered on the outside with a weatherproof sealant or self-expanding sealant. If the joint is insulated from the outside using a highly moisture proof material, the escape of moisture from the construction must be allowed through e.g., façade ventilation.

Avoid cold bridges. This means that the window must always be placed within the insulation layer and the joints created during placement must be filled using montage foam with little heat conduction.

Joints must be able to endure various movements and deformations of the building. Highly flexible sealants are the best for large windows, where it is recommended to use foams with higher elasticity due to linear expansions as a result of temperature and humidity changes, and for outer weatherproof sealing.

Provide sound insulation. During window placement, it is also important to seal cracks and leakage spots because it will help to improve sound insulation in addition to air tightness. Correctly-placed montage foam will mainly fulfil this requirement, but to fill smaller cracks, it is possible to use special sealants for this purpose, e.g., to fill a crevice between the inner window reveal and window jamb using acrylic sealant.

Provide fire resistance. Use only certified products with increased fire resistance and sensitivity for the placement of fire rated windows!

Read more about energy efficient solutions here.

*Article from the journal Inseneeria 02/2019 by Gerli Ramler