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report u values

3. Background

3.1 EUROPEAN HEATING AND COOLING DEGREE DAYS MAPS

3.1.1 Definition heating/cooling degree days

Heating degree days express the severity of the cold over a specific time period taking into consideration outdoor temperature and room temperature. For calculating heating degree days of European cities, weather data where taken from METEONORM and calculated to heating degree days (HDD) using the methodology applied by EUROSTAT, which form a common and comparable basis. External and internal building conditions may require additional energy for cooling and ventilation in order to meet a defined comfort level. This comfort level may be defined in building regulations or be given as user specifications. In order to meet the comfort conditions quantification of the energy for cooling is either based on the number of corresponding Cooling Degrees (similar to the number of Heating Degrees) or resulting from a iterative numeric calculation (as done in this study with the calculation program TRNSys) driven by maintaining the comfort level in the building at a given comfort temperature.

During preparation of this study EUROSTAT was working on a methodology to calculate cooling degree days. Because it had not been finalized, the methodology as applied in the US (ASHRAE) was used. Although meanwhile the US switched to a different approach developed by PNNL this does not really affect the conclusions of the study. The use of HDD and CDD for energy modelling is an approximation of reality, but acceptable for the purpose of the report.

The calculation methodology for HDDs and CDDs and a table of results for selected European cities is described in Annex 1.

3.1.2 European heating degree map

Based on the calculations of heating degree days, the following European map can be drawn:

 

Download in high resolution : EPS | JPG

 

It should be noted that due to the limited number of cities included in the map, the development of HDDs cannot fully represent all regional details.

3.1.3 EUROPEAN COOLING DEGREE DAYS MAP

Similarly, the following European map for cooling degree days can be drawn:

 

Download in high resolution : EPS | JPG

 

It should be noted that due to the limited number of cities included in the map, the development of CDDs cannot fully represent all regional details.