Energetic renovation of building stock

One third of the German final energy consumption is used for heating and hot water supply.1 This figure makes it clear that implementation of energy efficiency and the energy revolution in German can only be successful if it includes a systematic and high-quality energetic renovation of the building stock. This will result in a considerable level of construction activity over the coming years. In order to accept responsibility vis-à-vis coming generations in more than just the aspect of ultimately terminating energy resources, the resource consumption from construction thus caused should also be taken into consideration. To put it briefly: a successful energy revolution is only possible with resource efficiency, in other words a combination of energy and material efficiency.

The construction sector is characterised by long service lives and high investment costs. For this reason, measures for increasing energy efficiency should always be carried out with a high, sustainable insulation standard - such as that used in the passive house standard. Nobody wants to have to invest tens of thousands of euros in a fully-functioning structure yet again in one or two decades due to increased energy prices.

With regard to resource efficiency, existing building renovation is positive from two aspects: it is equivalent to only one third of material consumption as against to new construction and energy savings accrue.2

A myth: thick insulation packages consume more energy in manufacture than they can ever save

The sensibleness of energetic building renovation can be shown from a striking comparison. A detached house with 120 m² floor area and average thermal insulation properties requires around 1600 l of heating oil per year for heating. In this case, around 40% of the mineral oil required for heating over only one winter would be sufficient to manufacture a 25 cm thick facade insulation system made of expanded polystyrene (GPS), and therefore to drastically reduce the building heating oil consumption for decades to come.

Comparison of heating oil consumption over a heating period with mineral oil requirement for a complete EPS facade insulation (graphic: VDI ZRE GmbH / Marko Naujokat)

Despite this, the myth that the manufacture of very thick insulation layers requires more energy than possible savings over the service life is still around. In order to refute this, the following graph shows the energy consumption for insulation material manufacture compared with energy savings during the utilisation phase depending on insulation thickness. A wall made of 24 cm vertical core bricks was assumed for this comparison. An insulating material with a high manufacturing energy requirement (i.e. non-renewable primary energy), in this specific case GPS, was intentionally selected.

Comparison of energy requirement for insulation material manufacture and energy savings during the utilisation phase (image: VDI ZRE GmbH / Marko Naujokat)

It can be shown that the space heating saved over a 40-year utilisation period is considerably more than the energy required for product manufacture. An insulation thickness of up to 28 cm can even be saved within one year. Since numerous insulation materials require considerably less manufacturing energy than the EPS selected here, the balance is even more favourable in many cases.

1 Bundesministerium für Wirtschaft und Technologie (Hrsg.): Energiedaten, Berlin, 25.01.2012
2 UBA (Hrsg.): Rohstoffeffizienz - Wirtschaft entlasten, Umwelt schonen, 2010, S. 8

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