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Energy Efficiency


Energy Savings on a Prefabricated Block of Flats

Living in a Block of Flats
In most former communist countries there are quite a few prefabricated blocks of flats. In the Czech Republic, construction of the prefabricated buildings began in the mid-60s. The predicted life time of the buildings was estimated at about thirty years. Nowadays, most of these blocks are still used but they are usually in very bad condition due mainly to weather effects that directly influence the external construction. Since 1989, there has been an initiative to improve the quality of the buildings while at the same time increasing energy efficiency. Thus many blocks are getting renovated these days.

Beginning of the Project
The project initiated by the Vavrenova housing society started in 1998. It aimed at renovating and improving the energy efficiency of a 14-storey block of flats at Lhotka habitation in Prague. In its first stage, the project included thermal insulation and replacement of balconies. The building was constructed in 1965 and is oriented to the north. There are around 170 people living in 98 flat units. The heating system used to be supplied by Krc heating plant, situated in Prague and using natural gas. Since September 2001, distribution of heat has been connected to the Praha-Melnik co-generation plant, which burns north-bohemian lignite. The heating season lasts 216 days.

The reasons the housing society decided to go for thermal insulation were to improve the comfort of inhabitants and achieve energy savings, since there was an inefficient use of heat energy and energy for heating water. The inefficiency was particularly caused by inconvenient insulation characteristics of the external material and by the behavior of the inhabitants.

Financial Restraints
The housing society formed by the inhabitants of the building became independent in 1995. At that time the society didn´t have enough financial resources to realise such a project. Later, because of high energy bills, the board of the housing society, after an agreement with the members, decided to explore the possibilities of the project and in 1998 began to take necessary steps such as looking for suitable companies who would be able to realise the idea.

Results of the Energy Audit
In 2000, an energy audit was performed by Ekowatt, a renewable and energy conservation center, in order to ask for a financial support from the government. The audit determined energy savings potential. It presented and evaluated three possible options of energy efficiency measures that could have been taken into account. Finally, Ekowatt recommended that the society adopt the option of thermal insulation of the external walls would be done. As a low cost measure, Ekowatt proposed reparation of the windows on the north side and reconstruction of the heating system. The energy audit also recommended informing all of the inhabitants about the right way of aeration. The overall energy savings of the suggested option were calculated at 1.195 GJ per year, which represents a 34,6 % energy savings compared to the previous state. This number includes the consumption of energy for heating water as well.

Economy of the Project
The overall cost of the thermal insulation suggested by Ekowatt came to 129.000,- EUR. The audit counted on government support of 15%, which meant around 18.750,- EUR. Finally the housing society got just 12.500,- EUR (or 10%) from the government. Work on the thermal insulation and replacement of balconies was finished at the end of 2001. The actual cost increased to around 184.000,- EUR, including the balconies. The higher cost of the project was caused by the higher prices of the chosen company. Of course the project could have been realised for a lower cost but the inhabitants prefered to hire a rather costly but well known company. Till now the housing society has been able to cover 106.250,- EUR from its internal sources by increasing its repairs fund. The rest of the money was borrowed from the company. The society pays the firm 3.125,- EUR on a monthly basis, and the total claim should be paid up by 2004. In the near future the society would like to reconstruct the heating system, since there is no regulating mechanism at present and legislation has been enacted. It will require an additional 15.625,- EUR. If the housing society is able to get enough money together (6.250,-EUR) the windows on the north side will be also renovated.

Energy efficiency projects on prefabricated buildings do not come very favourably, because the return of investment is usually very long. The return of the investment of our project was estimated at 15 years. Most of these projects function as a chain reaction. Once there is a prefabricated block of flats in the neigbourhood getting renovated, the inhabitants of the building next door are willing to start the project on their own building.

Name and type of project
Energy Savings on a Prefabricated Block of Flats
Starting year 1998
Overall costs of the project

184.000,-EUR thermal insulation and replacement of balconies
15.625,-EUR renovation of heating systém (not realised as yet)
6.250,-EUR reparation of north side windows (not realised as yet)

Energy amount saved 1.195 GJ / year estimated cost of GJ is 10,-EUR
12.136,-EUR per year
New local jobs  
Number of similar projects many
Contact person
Karel Balik, Bytove druzstvo Vavrenova
Vavrenova 1170/80, Praha 4142 00, Czech Republic.
Ph:: +420 2 41492057