Färjestadsskolan – an economical- and environmental comparison of the framework materials prefabricated reinforced concrete and CLT for an elementary school

In today’s society the environmental impact of the construction industry is a major problem. Something that should be pursued is a more sustainable construction in which economic, social and environmental sustainability cooperate. The choice of building materials plays a significant role in creating a more sustainable development. In order to further encourage the development within sustainable building materials, the public sector is an important participant. In Karlstad, the municipality has decided to build a new school building in the residential area Färjestad. In this study, two different framework materials will be compared through an economical and environmental perspective where social aspects are considered in form of sound and fire requirements. The materials that will be compared are cross-laminated timber, CLT, and prefabricated reinforced concrete. The purpose of the study is to find out which of the materials is most economically and environmentally advantageous. In a school building, high demands are made regarding sound reduction and fire safety, which must be taken into account while calculating dimensions of the framework materials. The materials that will compared differ in several ways. Reinforced concrete has a high mechanical strength and is heavy which makes it steady and favorable to be used in tall buildings. Concrete is inorganic which also makes it fire and moisture resistant. CLT is made of minimum three layers of cross-glued wood boards which creates a stable and isotropic building material. In relation to its light weight CLT has great mechanical properties. Wood in general is an organic and combustible material, however cross-laminated timber has relatively good fire and moisture properties. In order to reach a result extensive calculations are made to decide the proportion of the two framework materials. The dimensions that are calculated are used to further calculate the costs of the project and the amount emissions of carbon dioxide equivalents. The economical calculation is primarily calculated by using BidCon. To calculate emissions of carbon dioxide equivalents, environmental product declarations, EPD, are used. The EPD: s reports the global warming potential for each material. The result of the economic calculation shows that a framework of CLT is slightly more expensive than a corresponding framework of prefabricated reinforced concrete. The calculations of carbon dioxide equivalent emissions show that the reinforced concrete contributes to more than twice as much emissions as a framework of CLT. From an economic perspective, prefabricated reinforced concrete framework is more profitable, but from an environmental perspective, cross-laminated timber is more beneficial