Energy use in the world is continuously increasing. In the last 30 years the use of primary energy worldwide has more than doubled and it is mainly supplied with fossil fuels. A more efficient use of energy in the built environment has to be pursued if a more sustainable development is to be attained.

The housing sector accounts for a major share of the energy use. Both in residential and commercial buildings, energy is mainly used for heating. Heat is energy with low quality. Traditional energy analysis methods, by failing to consider the energy quality, cannot give a holistic insight of the potential for reducing the energy used in the built environment. Exergy, instead, provides a tool to quantify the energy quality based on thermodynamic grounds.

In this thesis a methodology based on both the reduction of the energy demand and exergy demand in buildings is proposed to mitigate the problems related to the energy use in buildings through a reduced and more efficient use of energy.

The complex relations between building parameters to reduce the energy demand are managed with parametric analysis tools. The potential for energy demand reduction is investigated by means of screening analyses, local sensitivity analyses and global methods. A method for assessing the potential reduction of the energy demand in existing buildings and to evaluate the cost-efficiency of renovation measures based on the screening analysis is introduced and tested on two building typologies. In parallel, a program tool for parametric energy simulations, Consolis Parametric, has been developed on the core of an existing dynamic software, Consolis Energy +.

Factorial analysis has been used to investigate the relations between the reduction of the energy demand and of the energy supply when ground source heat pumps are used for heating and cooling. Optimal configurations- dependent on the insulation of the building- of number of boreholes and spacing were identified for minimum electricity consumption.

In the second part of this thesis exergy is used as tool for the definition of the efficient energy use in the built environment. The analysis of a multi-step heat pump to supply energy at two temperature levels, for space heating and domestic hot water production, exemplified how the reduction of the exergy loss can lead to a more efficient use of energy. The analysis was performed by means of SEPE, a modular software program developed in this work for exergy analysis in buildings.

For the systematic reduction of the exergy losses in the built environment, an important prerequisite is the reduction of the exergy required by the building. Systems like floor heating and cooling, based on low difference emission temperature, are examples of low-exergy systems. Buildings with reduced need of exergy input increase the efficiency of systems like heat pumps and enhance the use of low quality energy, like waste heat and energy from low temperature renewable sources.

The main aim of this thesis is  to demonstrate and critically assess life cycle approaches’ and environmental certification (EC) tools’ potential for supporting decisions for improved environmental performance in the building and real estate sectors.

Using life cycle approaches, the thesis shows that for new build and renovation cases aiming for low operational energy use that embodied global warming potential (GWP) due to material production can constitute a large portion of a building’s lifetime GWP. Therefore life cycle based information about materials’ embodied GWP needs to be made available to and utilized by design process decision makers.

It was also shown that applying the Swedish EC tool Miljöbyggnad was useful in highlighting potential positive and negative changes in indoor environmental quality arising from renovation packages aiming at significant operational energy use reduction in existing multifamily buildings. However such renovation packages are not profitable from a property owner perspective. Miljöbyggnad may be useful when designing policy instruments to overcome this.   

The thesis also showed that EC and related environmental enhancements contribute to achieving property owners’ and tenants’ overall strategic objectives for value creation. For property owners this arises for example through lower energy costs and attracting desirable tenants. For tenants, value creation arises as support for internal and external environmental communication.

For the further development of life cycle approaches’ and EC tools’ application to buildings and real estate it is important to consider how they can be adapted to consider ‘distance to sustainable’ targets referencing for instance the planetary boundaries approach. It is also interesting to investigate how valuation of buildings and real estate may be performed in a way that expands from the current narrow focus on the economic perspective to also include environmental and social perspectives.