SUSTAINABILITY 18 Phase 2 – use: Energy requirement During the use, energy consumption, and the maintenance and repair of a building play a key role. In heat insulation, timber houses are at the highest standard. By nature, wood has air-filled cells whereby heat and cold are conducted to substantially lesser extent than in other building materials. During the winter, the cold penetrates only to insignificant extent and during the summer the heat is kept outside. Even in the standard construction design, timber houses keep effortlessly within the consumption values mandated by law. With sufficient insulating layers, the passive and 3-litre construction design is easily realised with the timber house. The low residual energy requirement enables a correspondingly small dimensioned heating system. According to the Austrian standard ÖNORM B 2320 a useful life of at least 100 years can be expected for timber houses constructed professionally. Phase 3 – recycling, sorted dismantling and demolition The recycling capacity of buildings and building materials is becoming increasingly important due to the future shortage of resources. The waste of residual construction masses consisting of construction rubble and concrete debris is around 5 million tonnes per year, which accounts for 18% of the entire construction waste. In the analysis of the waste accumulated during dismantling, a reduction of the waste volume is indicated with the increasing application of timber construction designs. Furthermore, the wastes resulting from this indicate a high potential for utilising the material and the energy, whereas the utilisation efficiency can be further raised through the development of construction designs that are appropriate for recycling. The aspiration of integrating the installed elements and components as far as possible in another constructive lifecycle is therefore closely suggested. Here, the monolithic and homogeneous construction design of cross laminated timber CLT BBS must be considered to be very advantageous, as it omits an additional material separation. “Today’s” choice of materials thus affects “tomorrow’s” wastes, which is why it must already be ensured in the planning process that materials are installed in such a way that they are easily available and broken down at the end of the lifecycle, and so that they can be used in the optimal way in terms of their components (“design for recycling”) or for energetic purposes (“design for energy”). In this connection, the timber construction design has an advantage, as wood can be manipulated more easily and be demounted ideally and be re-used as a complete component in high quality. The lifecycle will then start over again. This way, a timber house that is dismantled after its use does not leave any non-recyclable rubble but useable wood. Individual components or elements can be re-used or be returned to the manufacturing process. The remaining wood is added to energetic use. This way, the CO2 continues to remain bound in each piece of installed wood and it thereby does not reach into the atmosphere for until the wood is used thermally in the last recycling step.
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