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The European Union aims to reduce energy use and CO2-emissions by 40 % by the year 2030. The building sector has been identified as having a great potential to reduce emission of CO2 by increasing its energy efficiency. Also, there is a growing concern of the buildings environmental performance, that lead to the development of building environmental assessment tools. However, different types of energy sources and confusing environmental impacts affect the decision making when renovating for improved energy efficiency. This study develops and tests a methodology to help decision-makers when considering major renovation of their building stock when connected to adistrict heating system. The proposed methodology is applied and used to investigate how different renovation scenarios affects the building environmental impacts in terms of CO2 emissions and identify and discuss future improvements of the methodology.

The novelty of the method is the expanded system boundaries that include both the distribution and production of district heating and the energy use at a building level. In this way it is possible to compare and weight measures made both at the energy system level and the building level. This work has limited its approach to energy use in buildings, but it is important to bring the life cycle thinking to the methodology. During the choice of the renovation methods it was noticed that the environmental impact of the production of some components in order to reduce the energy use of a building are not insignificant. Even if all the renovation measures considered in this case study are feasible, it is important to determine in which order they are desirable or achievable from an economic point of view. Uncertainty in the future development of energy, and limited economic resources can play an important role in the possibility of energy efficient renovation.

Den Europeiska Unionen har som målsättning att minska energianvändning och utsläpp av växthusgaser med 40 % till året 2030 jämfört med 1990. Byggnader har identifierats som ett område med stor potential för utsläppsminskningar om de energieffektiviseras. Användningen av olika energislag och olika sätt att värdera miljöpåverkan påverkar beslutsfattandet i samband med energieffektivisering.

I studien utvecklas och testas en metodik som kan hjälpa beslutsfattare vid renovering med energieffektivisering inom fjärrvärmeområdet. Först utvecklades en översiktlig metodik vilken inkluderar både byggnadsenergisimulering och energisystemsimulering. Sen implementerades metodiken genom olika renoveringsscenarier och utsläppen av växthusgaser analyserades.

Metodiken visar att det finns en möjlighet att utveckla ett verktyg som kan hjälpa beslutsfattare när energibesparingsstrategier ska implementeras vilka kan bli positiva för både byggnader och fjärrvärmesystemet.