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Energy efficiency measures in buildings are considered to have great potential in order to reduce total energy consumption, and thus contribute to a reduced environmental impact and a better climate. In Sweden, however, the energy performance requirements for buildings are formulated in terms of bought energy, i.e. as bought electricity and district heating (DH), which does not always reflect the environmental and climate impact from a broader perspective. Focusing on bought energy means that many choose an electricity-based heat pump solution in their building instead of DH, since heat pumps result in a smaller amount of bought energy compared to DH.

The surrounding energy system of the buildings is affected by the choice of energy carriers used for heating. How the energy system is affected is studied in this thesis using two different methods. In the first part, primary energy consumption has been calculated for a simulated building with different heating solutions, representing different electricity and DH demands. In the second part, the impact on total consumption in the surrounding power and DH networks due to different market shares of electricity-based heating and DH has been studied. The second part also includes an analysis of the potential to produce electricity using combined heat and power (CHP) in different scenarios depending on the market share of DH. This part has been carried out as a case study for the Swedish municipality of Falun.

The results show that the choice of energy carrier has a great influence on primary energy consumption. The resulting primary energy consumption does, however, to an even greater extent depend on the calculation method used. Which heating solution, and thus also which energy carrier, gets the lowest primary energy consumption varies in the different methods.

The surrounding power and DH networks are also affected to a great extent by the choice of energy carrier. There is a huge potential to lower peak demand in the power grid by avoiding electricity-based heating. The potential to produce electricity using CHP is also increased with a larger market share for DH. In Falun, reduced electricity demand and increased electricity production using CHP make it possible to cover the peak power demand using only electricity production from CHP. In comparison, 10 % of the peak power demand was covered by electricity from CHP in 2015.

The choice of energy carrier for heating in buildings affects the surrounding energy system to a high degree, and is therefore an important aspect to take into account in both local, national and global energy efficiency projects. 

The high energy use in the European building stock is attributable to the large share of old buildings with poor energy performance. Energy renovation of buildings is therefore vital in the work towards energy efficiency and reduced environmental impact in the EU. Yet, the strategies and energy system implications of this work have not been made clear, and the rate of building renovation is currently very low.

The aim of this thesis is to investigate the economic and environmental aspects of energy renovation strategies, with two main objectives:

• Renovation of Swedish district heated multi-family houses, including life-cycle cost and environmental analysis and impact on the local energy system;

• Renovation of European residential and office buildings, including life-cycle cost and environmental analysis and influence of climatic conditions.

Buildings typical for the respective regions and the period of construction 1945-1970 were simulated, in order to determine the feasibility and energy saving potential of energy renovation measures in European climates. A variety of systems for heating, cooling and ventilation were studied, as well as solar energy systems, with focus on heat pumps, district heating, low-temperature heating systems and air heat recovery.

Compared to normal building renovation, energy renovation can often reduce the life-cycle costs and environmental impact. In renovation of typical European office buildings, as well as Southern European multi-family houses, more ambitious renovation levels can also be more profitable.

Exhaust air heat pumps can be cost-effective complements in district heated multi-family houses, while ventilation with heat recovery is more expensive but also more likely to reduce the primary energy use. From a system perspective, simple exhaust ventilation can reduce the primary energy use in the district-heating plant as much as an exhaust air heat pump, due to the lower electricity use.

Byggnadssektorn står för omkring 40 % av den totala energianvändningen i EU. Den höga energianvändningen i Europeiska byggnader kan till stor del tillskrivas den stora andelen gamla byggnader med dålig energiprestanda. Energirenovering av byggnader, eller energieffektivisering genom renovering, kan därför anses utgöra en central del i arbetet mot EU:s klimat- och energimål för år 2030. Trots detta är det ännu inte helt klarlagt vilka strategier som ska tillämpas för att uppnå detta och hur det påverkar energisystemet, och i nuläget är renoveringstakten fortfarande väldigt låg.

Målet med denna avhandling är att undersöka ekonomiska och miljömässiga aspekter av strategier för energirenovering, såväl byggnadsskalsåtgärder som aktiva system, för typiska bostads- och kontorsbyggnader i Sverige och i andra Europeiska regioner. Mer specifikt har arbetet följande två inriktningar:

• Renovering av svenska, fjärrvärmevärmda flerfamiljshus, inklusive livscykelkostnadsanalys och livscykelmiljöanalys samt påverkan på det lokala energisystemet;

• Renovering av Europeiska bostads- och kontorsbyggnader, inklusive livscykelkostnadsanalys och livscykelmiljöanalys samt påverkan av klimatförutsättningar.

Byggnader typiska för respektive region och byggnadsperioden 1945-1970 modellerades och användes i simuleringar för att fastställa den övergripande möjligheten och energibesparingspotentialen för olika renoveringsåtgärder i Europeiska klimat. En rad system för värme, kyla och ventilation studeras, samt solenergisystem, med fokus på värmepumpar, fjärrvärme, lågtemperaturvärmesystem och värmeåtervinning ur frånluft.

Jämfört med renovering av byggnader utan energieffektiviseringsåtgärder kan energirenovering i många fall minska såväl livscykelkostnaden som miljöpåverkan. Vid renovering av typiska Europeiska kontorsbyggnader lönar det sig mer att renovera ner till ett uppvärmningsbehov på 25 kWh/(m²∙år) än 45 kWh/(m²∙år), då den minskade kostnaden för köpt energi väger upp den ökade kostnaden för isolering. För flerfamiljshus i södra Europa kan mer ambitiösa mål gällande värmebehov också vara lönsamma, medan en mer måttlig nivå är lämplig för småhus.

Solvärme- eller solelsystem kan användas för att minska byggnaders miljöpåverkan. Utan subventioner eller inmatningstariff för överskottsel kan det bli svårt att få lönsamhet i dessa system för kontorsbyggnader i Nord- och Centraleuropa samt för småhus. För flerfamiljshus kan solenergisystem dock sänka den totala livscykelkostnaden, såväl i södra som i norra Europa.

Värmeåtervinning och lågtemperaturvärmesystem visade sig båda ha större inverkan i kallare klimat. Lågtemperaturvärmesystem förbättrar värmefaktorn för värmepumpar, i synnerhet när uppvärmningsbehovet är stort i förhållande till varmvattenbehovet. Vid renovering av byggnader med vattenburna radiatorer kan konvertering till tilluftsradiatorer sänka framledningstemperaturen i värmesystemet.

I svenska flerfamiljshus kan frånluftsvärmepump vara ett kostnadseffektivt komplement till fjärrvärme, medan från- och tilluftsventilation med värmeåtervinning är dyrare men mer sannolikt att ge en minskad primärenergianvändning. I ett systemperspektiv kan frånluftsventilation utan värmeåtervinning minska primärenergianvändningen i fjärrvärmeverket lika mycket som en frånluftsvärmepump, tack vare den lägre elanvändningen.

Energy efficiency measures in buildings are considered to have great potential for reducing total energy use, and contribute to a reduced climate and environmental impact. In Sweden, however, there is a focus on bought energy, which does not always reflect the environmental and climate impact. Focusing on bought energy means that a house owner may choose an electricity based heat pump instead of district heating (DH), since heat pumps result in less bought energy compared to DH.

The energy system surrounding the buildings is affected by the choice of energy carriers used for heating. This thesis uses three different methods to study how the energy system is affected. In the first part, primary energy use has been calculated for a simulated building with different heating systems, resulting in different electricity and DH demands. The second part studies the impact on peak demand and annual consumption in the power grid and DH system due to different market shares of electricity based heating and DH. In the third part, the life cycle cost is calculated for different heating solutions from both a building and a socio-economic perspective, for 100 % renewable energy system scenarios.

The results show that the choice of energy carrier has a great influence on primary energy use. However, this depends even more on the calculation method used. Which heating solution, and thus which energy carrier, gives the lowest primary energy use varies with the different methods.

The power grid and DH system are affected by the choice of energy carrier. There is a potential to lower peak demand in the power grid by more efficient heat pumps. But an even greater potential is shown by using DH instead of electricity based heating. A larger share of DH also allows the production of more electricity with the use of combined heat and power.

The life cycle cost for different heating solutions also depends on the method used. From a building owner’s perspective, with current electricity and DH prices, electricity based heating is more economical. However, from a socio-economic perspective, with increasing electricity system costs due to a larger share of variable electricity production in a 100 % renewable system, DH becomes more economically profitable in several scenarios.

The choice of energy carrier for heating in buildings affects the energy system to a high degree. A system perspective is therefore important in local, national and global energy efficiency policies and projects.