KARLSRUHE Platform

Background of the housing stock and the social housing organization

Volkswohnung GmbH is the municipal housing company of Karlsruhe, founded in 1922 by the city administration to overcome the shortages in municipal dwellings after WW I. The city of Karlsruhe is still the main shareholder of the company.

The main responsibility of Volkswohnung is to provide affordable dwellings of good quality to the citizens of Karlsruhe and to contribute to the urban performance by high quality architectural and urban planning.

At present, over 14.000 dwellings are rented. Two third of them have been constructed by Volkswohnung, the others purchased. In addition, a major number of buildings are managed for third parties by commission.

After the big construction program between 1950 and 1970, the current objectives are focused on refurbishment and quality improvement. Among this, energy conservation and efficient generation of energy for heating and tap water preparation is the essential part of retrofit measures, using cogeneration and waste heat utilization and including also the use of renewable energies where available.

Volkswohnung is continuously looking for new approaches and technologies to support its aims to increase the sustainability of its building stock. During its retrofit program over the past 20 years with almost 200 mill. € spent so far the average consumption of primary energy has already been reduced by about 50 % (from 250 to 135 kWh/m2 for the supply of heating energy and domestic hot water), with a cut by another 50 % of the present value viable.

Video material about the project

Extended version with regard to the platform implemented in Karlsruhe, the material is only available in German. General video footage of SAVE@Work4Home is available here.

Former situation of energy management by the tenant

Most of our buildings are supplied by a central heating system, based on district heating or gas central stations. Only a few of them still have a decentralized supply, in most cases gas-boilers for individual dwellings or gas stoves for room heating. In these cases, tap water is prepared decentralized by boilers operated either with gas or with electricity. Oil or other fuels are not used in our buildings any more. By Volkswohnung's current renovation program, decentralized heating systems are regularly replaced by central heating stations.

Tenants with decentralized energy supply are billed by the energy supplier (the city works of Karlsruhe) once a year, usually in January. In these cases, the annual consumption of gas or electricity per dwelling is measured by gas or electricity meters. In contrast, tenants with central supply of heating energy and domestic hot water get their invoice on annual energy costs by Volkswohnung, regularly about 6 months after completion of the billing period. In this case, the total energy consumption of the whole building is "distributed" to the individual dwellings according either to measurements by heat meters, if installed, or by certain calculation rules, which are prescribed by regulation, if meters are not available in the dwellings. Accordingly, the information on energy consumption is rather imprecise and, in any case, too late for a direct feed-back from consumption to behaviour.

From detailed measurements we know that there are very large differences in the energy consumption in dwellings, even within one building, due to different user habits (and due to other reasons). There are estimates that there is an energy saving potential of 20 % or even more, by setting the room temperatures correctly, improving ventilation habits and shut-down of heating when not needed. Due to a lack of information, this potential is not realized in practice. The need of user habits feed-back was also confirmed by the survey.

In the dwellings of Volkswohnung, almost all radiators are equipped with thermostats to control the room temperature. Some newly refurbished buildings have an extended possibility to regulate the temperature: Instead of the normal thermostat a wireless thermostat is adapted to the radiator. This wireless thermostat is controlled by a central programmable unit. Heating times and the room temperatures for every room in the dwelling can be programmed for each week day by the tenants. In these buildings, automatic ventilation systems are used which replaces natural ventilation with windows.

The survey has shown that only some of the tenants are able to use this modern equipment correctly, despite information brochures which are handed to the tenants after refurbishment. 40% of the tenants in the survey felt badly informed about possibilities to save energy. Around 35% also feel badly informed about their own energy consumption. To realize saving potentials, new approaches have to be found to overcome the existing barriers.

Reasons and motivation for the social housing organisation

Volkswohnung's motivation is to reduce energy costs for their tenants both by building refurbishment and by enabling the tenants to save energy without reducing comfort as part of a long-term sustainability strategy. The aim is to achieve a maximum of energy conservation by a minimum of expenditure.