Jämförelse av klimatpåverkan från industriellt producerade och traditionellt platsbyggda flerbostadshus

Sammanfattning: COMPARISION OF CLIMATE IMPACT FROM INDUSTIALLY PRODUCED AND TRADITIONALLY SITE-BUILT APARTMENT BUILDINGS  Greenhouse gas emissions is a global problem that is causing climate change on our planet. In Sweden, the construction and real estate sector accounts for about 21% of the total emissions. The focus has previously been on the climate impact of a building's operational phase. By constructing new buildings with lower energy requirement for heating, an increased use of renewable energy and more energy-efficient supply systems has lowered the emissions in the operational phase. This in turn led to the construction phase becoming more important in terms of the building's total climate impact throughout its lifecycle. The concept for industrial construction means that large parts of the construction take place in a factory and are often emphasized as energy efficient. Important for the construction phase is also the choice of building materials and wood, as renewable material has a lower climate impact than for example concrete. In industrial construction, wood is well suited as a building material because it is easy to handle in the factory and it is a straightforward material to transport. This entails an energy- and resource-efficient construction process.    The purpose of this work is to analyze differences in climate impact between industrialized construction process and traditional site-built construction process. It is also analyzed how these differences are made visible or not in traditional reporting of LCA in life cycle modules where the entire life cycle is not always reported. Three different buildings are compared: an industrially produced wooden house, a site-built wooden house and a site-built house with a concrete frame. In addition, the LCA for the industrially built wooden house is reported in two different ways to make it clear that the LCA methodology is not adapted for industrial construction.     The results show that if the construction site is close to the factory, there is a clear advantage of building industrially. But the distance from the factory to the construction site for industrial construction for the industrial construction accounts for such a large part of the climate impact that at longer distances within Sweden it can often be the case that a site-built process would have given a lower climate impact. If, of the other hand, the construction site is closer to the factory, the result shows a clear climatic advantage of building industrially. Building industrially instead of site-built provides a climate advantage in energy use in the construction and installation process as well as a small reduction in climate impact in terms of waste.   It also shown that unfair comparisons can occur between industrial and site-built houses if the entire life cycle is not reported, where industrial construction then gets higher climate impact in the product phase because the construction that take place in the factory is counted as product manufacturing and not as construction site.   The prefabricated process is well suited for building in wood. The study shows that a prefabricated wooden house emits approximately 40-45% lower carbon dioxide emissions than a site-built concrete house in the product phase.