How energy renovations of older buildings can reduce energy use

Energy renovation of older multi-family buildings can nearly halve energy use. When considering costs, it is usually better to renovate a building than to demolish it and build a new one. These are the conclusions of a thesis recently presented at LiU.

Lina La Fleur outside a construction site at Campus Valla, Linköping University. Photo credit: Mikael Sönne

Stångåstaden in Linköping

Many of the multi-family buildings built during a period of intense construction in Sweden in the 1960s and 1970s (known as the “Million Programme”, or in Swedish “Miljonprogrammet”) are still awaiting renovation. One important question for property owners is whether – and, if so, how – the properties should also undergo energy renovation, or in other words, whether they should be refurbished to reduce energy consumption.

In her doctoral thesis “Energy renovation of multi-family buildings in Sweden. An evaluation of life cycle costs, indoor environment and primary energy use, and a comparison with constructing a new building” Lina La Fleur analyses the results of the energy renovation of a multi-family building in Linköping built in 1961. The property, located on Barnhemsgatan and owned by the municipal housing company Stångåstaden, consists of twelve apartments.

Measuring indoor climate in apartment.

The energy renovation was carried out at the same time as traditional renovation, and consisted of three measures: additional insulation of façade and attic, the installation of new windows, and the switch to a ventilation system with heat recovery.

Energy consumption was reduced by 44%, a major saving. Installing the new ventilation system was the most significant measure taken.

“And it must be remembered that the energy consumption of this building was not unusually high from the start. In other words, the energy renovation that I studied was an ambitious project”, says Lina La Fleur.

Improvement for the tenants

The measures improved not only the energy efficiency of the building, but also the indoor environment in the apartments. Both the temperature and the air quality were experienced as more comfortable than before the renovation. The only negative effect was that some of the residents experienced disturbing noise from the ventilation system.

“We asked the residents to complete a questionnaire during the winter, but our simulations suggest that the building may become somewhat too warm in the summer. The insulation will turn it into a thermos flask. But if this happens, you can always open the windows or reduce direct sunlight in various ways”, says Lina La Fleur.

Equipment for the measuring.

When considering the life cycle costs of a property, it is cheaper to renovate an older residential building than it is to demolish it and build a new one. This is true, even if the energy consumption of a new property is normally even lower than it is of one that has undergone energy renovation. Only in certain cases is it possible to achieve the same energy efficient in an older property as in a completely new one.

“I don’t want to make an unequivocal recommendation, but – yes, it often makes more sense to energy renovate than to build from scratch. But if the property is damaged or if there are other special circumstances, it can be better to demolish it”, says Lina La Fleur.

“The analysis is only valid in cases when the energy-efficient measures are carried out when the property is to be renovated for other reasons. In this case, the scaffolding that is already in place can be used, which reduces costs. Further, the residents may have been relocated to other, temporary, accommodation.”

Not just economy

A property owner who is solely interested in achieving the lowest possible cost, however, should not carry out major energy renovation, and indeed – in certain cases – no energy renovation at all. This is also one of the conclusions of the thesis. Despite the major savings in energy, the costs of the measures are not regained in lower energy costs. The price of energy is far too low for this.

“Yes, that’s how it is, which is rather disappointing. But an energy renovation brings with it many other benefits”, says Lina La Fleur.

“And it must be remembered that Sweden has set goals for reducing energy consumption in the building sector. I also show in the thesis which measures are most cost-effective for various energy-saving targets.”

The work presented in the thesis includes both computer simulations of the various measures and measurements in a particular building. In addition to the building in question, three typical building types in Sweden from the 1940s, 1950s, and 1970s were subjected to computer analysis.

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