28 May 2021

A new strategy for the energy renovation of older residential buildings would open opportunities to save both energy and money, while reducing impact on the climate. The current guidelines lack refinement, and do not take sufficient consideration of the type of building. These are some of the conclusions in a thesis recently presented at LiU.

Visby historical center.
Visby historical center. onfilm

Energy saving for small buildings

Portrait Vlatko Milic.Vlatko Milic.

The residential and service sector (offices) accounts for 39% of energy use in Sweden, and has a profound impact on the climate. The housing stock is relatively old, with around 25% of the properties being built before 1945. These properties often have poor insulation and consume considerable amounts of energy.

In his thesis A techno-economic system approach for the energy renovation of residential districts built before 1945, Vlatko Milic investigates how best to energy renovate these buildings, taking into consideration life-cycle costs, energy consumption, and the preservation of any cultural heritage value of the building.

The investigation is based on 73 multi-family buildings in Vasastan in Linköping, and twelve building types found in the historical town centre of Visby.

Different building materials

The thesis presents a strategy for energy renovation that incorporates both financial considerations and environmental impact as regards both property owners and district heating companies. The analysis is conducted at four levels – building, cluster, district and city – and includes both building material (stone or wood), basement type, and the presence of any adjoining buildings.

Different houses constructed before 1945.Houses in Linköping that are part of the investigation.

This can be compared to the currently valid guidelines that consider only geographical position, type of heating, and whether the building houses one or several families.

“There are major differences between the properties, and the goals of an energy renovation should be tailored more closely to the particular building than is presently the case”, says Vlatko Milic, who hopes that his research results will be put to practical use.

“Indeed! A more precise strategy can identify the potential for saving energy that is optimal from a cost perspective. This will aid property owners to find incentives to energy renovate properties.”

Environment and economy

The thesis shows that energy renovation rapidly brings large environmental benefits, but that these depend on how the energy used is produced. In a life-cycle perspective, up to 50 years, renovation was financially profitable for all of the properties investigated. The size and timing of the cost savings depend partly on the individual property, and partly on the measures taken (additional insulation, new windows, or a new heating system).

Different houses constructed before 1945.Different houses in Visby.

“To put it simply, you can say that the worse the initial situation, the greater the potential”, says Vlatko Milic.

Single-family buildings of stone had the poorest thermal performance. In this case, the optimal energy efficiency measures reduced energy consumption by 70-78% and life-cycle costs by 34-37%. In contrast, wooden multi-family buildings had the best thermal properties, and the corresponding reductions were 23-24% and 14%, respectively.

The energy signature

One problem of energy renovation is that it has a negative effect on district heating suppliers. This is made clear when considering the second perspective – that of the energy suppliers – in the strategy that Vlatko Milic presents. While it is true that a company’s costs will fall when energy consumption is reduced, income will fall by a greater amount. This may lead to price rises.

“The interests of different actors differ, which is a difficulty. We should develop methods for energy renovation that also consider the district heating system”, says Vlatko Milic.

One of the five articles included in the thesis suggests how to improve what is known as the “energy signature”, which is used by many property companies and energy suppliers. It provides a simple way to show the energy needs of a building at different outdoor temperatures.


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