BPIE: Europe's buildings under the microscope - PU Europe

Prescriptive-based requirements for new buildings
Member States have different prescriptive, element-based requirements associated with building energy
codes such as maximum U values, minimum/maximum indoor temperatures, requirements for minimum
ventilation rates and boiler and/or air conditioning plant efficiency. Some of the prescriptive criteria
associated with the key requirements presented in Table 2B6 are further analysed below.
i. Insulation
Limiting the thermal conductivity of major construction elements is the most common thermal
performance requirement for buildings. These are based upon U value requirements (expressed in
W/m 2 K) for the main building envelope construction elements. These U values are worst acceptable
standards which as a stand-alone measure would not necessarily mean that a building meets the overall
performance-based requirements in the respective country.
Country by country data on “maximum” U value requirements for roof, wall, floor, window and doors
collected through the BPIE survey are shown in Figure 2B7. These are presented against the relevant
heating degree days per country or region. Given the diversity in climatic conditions, maximum U value
requirements vary widely across different countries where Spain, France, Greece, Italy and Portugal have
multiple maximum U values due to the considerable variation in climatic conditions within each country.
In some countries, variations also apply for different types of buildings (e.g. Latvia) and type of heating
(e.g. Sweden). A comparison between the collected data and the cost optimal U values published by
EURIMA/Ecofys 33 in 2007 (see Figure 2B7, blue line) confirm that Member State maximum U values are still
higher than the cost-optimal requirements, suggesting that U value requirements in most Member States
should be made more demanding. This was also one of the key findings of the IEA information paper on
building codes 34 where it was shown that existing U value requirements for building components did
not reflect the economic optimum. From Figure 2B7, it can be deducted that this is especially true for
countries of mild or warm climates reflecting the equivalent magnitude of effort that is required in those
countries. This comes as no surprise as countries in cold climatic zones have had longer traditions in
thermal building regulations and therefore stricter requirements.
ii. Air tightness/permeability and ventilation requirements
Most countries have introduced requirements to ensure minimum levels of ventilation within buildings.
These are generally based upon metabolic rates and activity within the building. The requirements
associated with ventilation relate principally to health, comfort and productivity; however they do
have direct impact on energy requirements. The thermal performance of buildings is directly related
to airtightness and the requirements for ventilation. Excessive ventilation as a consequence of poor
construction detailing, can lead to considerable energy wastage and for this reason a number of
countries have introduced requirements to limit the air permeability of buildings. Air permeability is
normally measured using a pressure test, typically at 50Pa (4Pa in France and 10Pa in The Netherlands)
to determine the air leakage rate. The requirement is typically expressed in m 3 /h.m 2 (where m 2 is the
external envelope area) or in the case of Denmark in l/s.m 2 (where m 2 is the floor area). Table 2B9 provides
a summary of key requirements for Member States which have adopted airtightness requirements.
33
U –Values for better energy performance of buildings EURIMA 2007 www.eurima.org/uploads/ModuleXtender/Documents/88/documents/
EURIMA-ECOFYS_VII_report_p1-65.pdf
34
Energy efficiency requirements in building codes, energy efficiency policies for new buildings, Jens Laustsen, International Energy Agency, March
2008
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