Monday 27 February 2012

Practical examples of retrofitting in Verden, Germany

A talk on a practical German example on the benefits and practical ways of retrofitting communal housing stock, as successfully applied in Verden.

This was a talk given at a wider Anglo-German meeting of a group with a common goal of ethical and energy efficiency in construction . Our hosts and organisers were Sandra and Leif TollĂ©. The talk was followed by a team building exercise at Bredbeck House, an hours drive from the city. My visit took place during the extremely cold period in February 2012, with outside temperatures reaching minus 15 degrees Centigrade.

Verden (Aller) is a small Cathedral city famous for being the site of a major battle (massacre) by Charlemagne, for its long links with mounted regiments and with the British Hannoverian Crown.

The slideshow features Verden and the participants in general,

The Anglo German delegation attended a talk by Olaf Heitkamp of Verden's communal housing company, Kreisbaugesellschaft des Kreises Verden mbH ( It was held in a cosy venue within the Holzmarkt, a historic military stables, renovated and converted into a cultural and shopping centre for the city.

The company has been in existence since 1922, providing housing stock for rent and of which some includes social housing. Currently, they are responsible for 1050 flats in houses. In Germany, properties are sized by the number of rooms, in contrast to the UK where we just count the bedrooms. The flats are described as being mostly three to four rooms in size, with an average of 2 residents per property.

They began retrofitting for energy efficiency in 1989, initially using wall insulation. However, this created problems with mould and so a full package including windows and roofs was included from 2011. Note that the lofts of these houses were 3m high and usable, the houses, like other German properties also have usable cellars.

From 2006 to 2010, the energy savings were already 37%.

Further specific examples were given. Base (or plinth) insulation and external insulation of nine houses with 6 flats each showed dramatic savings in heating oil use, from 104250 L in 2000 to 44000 L in 2010. Another project of six homes with five flats each that were heated using a gas fuelled generator for hot water and electricity reduced the 2010 gas use from 422000 cubic meters to 202800 cubic meters in 2011.

Another key lesson was whether it was better to retrofit or to demolish and rebuild. One project of three houses was costed at EURO 1.3m to retrofit, it was simply more economic to rebuild at the highest current standards, with the residents being offered housing elsewhere.

With the German national government giving subsidies for energy efficiency to the tune of EURO 1bn, the communal housing association is building more properties to an anticipated high standard, “EnEV 2012”.

The talk was extensive, with more examples. The overall tenor was of considerable experience in retrofitting and new-build to the highest energy standards suitable for each site or situation.

For more information and contact with author

For UK examples or Green build and retrofitting, see the following articles:

Historic buildings and future-proofing the skills to restore them: DE and GB experts meet in London

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