Minimum Performance Requirements for Windows

Minimum Performance Requirements for Windows

Minimum performance requirements for window replacement in the residential sector

 

As required by the Energy Performance of Buildings Directive, EU Member States have to set cost-optimal minimum energy performance requirements for the replacement of building elements such as windows.

The map and the table below illustrate how EU Member States have implemented this 2012 EPBD requirement and provide information on:

  • the minimum performance requirements set at national and regional level for window replacement in residential buildings (U- value, g-value, last update) Source: Ecofys
  • information about the conditions limiting the proper enforcement of the minimum performance requirements – SourceEcofys
  • similar requirements in Norway, Russia, Switzerland and Turkey – Source: Glass for Europe
  • the average performance of windows currently installed in each Member States (Source: European Commission – EU Building Database)

To Glass for Europe, three major conclusions can be drawn from this data:

  1. Europe’s buildings are largely equipped with inefficient glazing and it is urgent to support window retrofitting  
  2. Minimum performance requirements across Europe are not driving efficient window options
  3. Conditions restricting the applicability of minimum performance requirements need to be lifted

 

(*) Conditions apply

1 – It is high time to install better performing windows

The average insulation performance of the windows currently installed in Europe, illustrates the urgency of renovating the building stock to prevent that no more energy is wasted in buildings. U-values presented in most EU countries illustrate that a vast majority of the building stock is still equipped with either single glazing or early uncoated double glazing, i.e. products pre-1970-80ies, while mainstream glazing products are now between 5 to 10 times more efficient. However, renovating is not enough as replacing the current windows with suboptimal choices or simply apply the minimum performance requirements will not allow Europe to deliver on its energy and climate objectives. Since windows stay in building for almost 40 years, it is indispensable to ensure that the products installed from this time on are highly energy efficient so that they can keep on delivering energy savings for the coming decades.

2 – Inappropriate regulatory assessments drive sub-optimal choices

Most of the minimum requirements set by Member States re­fer to sub-optimal choices. Sometimes the minimum requirements are very close to or even below the energy performance of the least-performing windows sold today. In addition, Member States often take into account only the insulation properties of windows (U-value) and do not consider the heat gains (g-value). It is widely acknowledged that the energy balance, which combines solar heat gains and heat losses of the window into a single value, is the best available way to assess the energy performance of windows and set the minimum performance requirements. Only Denmark and the United Kingdom apply minimum requirements for windows based on the energy balance approach. Member States should be invited to apply the energy balance approach while assessing the energy performance of windows and put in place measures to support the uptake of high efficient windows.

3 – Regulatory way-out of minimum performance requirements impedes uptake of efficient products

In several EU countries, the minimum performance requirements apply under conditions, which restrict the proper enforcement of the EPBD. To deliver its full energy saving potential, minimum requirements shall apply from major renovation down to single window replacement. However, in 11 Member States, windows for the residential sector with a performance below the minimum requirements can still be installed on buildings. This is made possible because requirements apply only in case of major renovations or when a renovation permit is requested or when a minimum window area is to be renovated. This illustrates loopholes in the EPBD and Member States’ implementation of it which leads to sub-optimal windows still being installed across Europe. It creates barriers to the market uptake of energy efficient glazing in the residential sector.

 

EU Member States

Legal requirements

Uw – value

(W/m²K)

g – value

Last update

 

Austria

1.2 2015
Conditions: When performing a renovation in Austria either the above mentioned Uw-value (88%*1.4 = 1.2 W/m²K) needs to be fulfilled or a renovation concept needs to be developed ensuring the compliance with the energy balance requirements for the whole building. Building elements have not been investigated in the cost optimality report. The requirements also apply for single window replacements.

Belgium – Brussels

1.8 (Ug: 1.1) 2014
Conditions: This requirement applies / is enforced solely in case of renovation with a town planning permit. There is no need of a permit if only single windows are replaced. Therefore, the requirements do not apply for single window replacements.

Belgium – Flanders

1.5* (Ug: 1.1) 2016
Conditions: In addition to the average Uw-value requirement of 1.5 W/m²K a Ug-value of 1.1 W/m²K needs to be fulfilled. From 2015, all major building renovations (residential, offices and schools) involving 75% or more of the building shell or replacement of the whole HVAC system will have to meet a whole building energy performance requirement. This requirement applies / is enforced solely in case of renovation with a town planning permit. There is no need of a permit if only single windows are replaced. Therefore, the requirements do not apply for single window replacements.

Belgium – Wallonia

1.5 (Ug: 1.1) 2017
Conditions:U-value requirement might be updated in 2020. This requirement applies / is enforced solely in case of renovation with a town planning permit. There is no need of a permit if only single windows are replaced. Therefore, the requirements do not apply for single window replacements.

Bulgaria

1.4* 2015
Conditions: Valid for windows with PVC frame (further requirements: 1.6 / 1.8 – wood (walls / roofs), 1.7 – Aluminium, 1.75 / 1.9 – glazing facades / with higher requirements). The legal requirement is supposed to become Uw = 0.6 in 2020. An intermediate step of Uw 1.1 is discussed for 2018. It is unclear whether the requirements apply also for replacement of single windows.

Croatia

1.6 / 1.8* 2015
Conditions: Building specific requirements (first figure: buildings up to 2 floors; second figure: buildings with more than 2 floors). The existence of air tightness requirements was mentioned but not specified. In case where only certain building elements of the envelope of a heated part of the building covering a surface area over 25% are renovated, the U-value of the entire building element (for all types of buildings) shall fulfil the prescribed requirements. In case of external walls and transparent elements of the envelope of a heated part of the building covering an area over 25% of that building component or element, the provision from the previous sentence relates to each individual geographic orientation of that building part (Exception: Requirements related to the max. Allowed U-values are not applied to a glass window with a large surface up to 4 m² or if there is an additional barrier between such window and the heated indoor area of the building). Therefore, the requirements do not apply for single window replacements.

Cyprus

2.9* 2017
Conditions: As from 1st of January 2017 all buildings that undergo major renovation should reach at least energy class B as far this is technically and financially feasible. The requirements apply for single windows that are replaced in existing and new buildings.

Czech Republic

1.1 2018
Conditions: It is unclear whether the requirements apply also for replacement of single windows.

Denmark

-* 2015
Conditions: Danish energy requirements to windows in the Buildings Regulations are to the energy balance of the window not to the U-value and g-value separately. This is set to create possibility for manufacturers to focus on the total energy performance optimisation of windows instead of focusing on sub-optimisation of the U-value and g-value separately. The requirements concerning the energy gain are Eref > -17 kWh/m²a (windows) and Eref > 0 kWh/m²a (roof windows). This approach is compliant with EU regulation and welcomed by the industry but it makes it impossible to provide definite numbers in this report. Therefore, the requirements apply even if only a single window is replaced.

Estonia

-* 2013
Conditions: Estonian legislation do not set any requirements for the window’s thermal properties. No component based requirements exist. Energy efficiency of buildings is assessed through primary energy and requirements are set to the primary energy consumption. The minimum energy performance requirements are expressed as a primary energy performance indicator calculated for the building according to its standardised use, and applied to the building as a whole. Therefore, no requirements exist for single window replacements.

Finland

1.0* 2012
Conditions: The U-value of new windows and external doors must be 1.0 W/(m²K) or better. This requirement applies / is enforced solely in case of renovation with a town planning permit. A permit is needed if you exchange so many windows that the measure has a significant effect on the energy efficiency of the building. The threshold for an effect to be considered “significant” was not reported. Yet, in practice almost 100% of the renovation market were reported to fulfil the given U-values, as manufacturers reportedly don’t produce windows above these U-values just for “non-permit” cases. Yet, officially the requirements do not apply for single window replacements.

France

1.9* 2018
Conditions: The value (1.9 W/m²K) is valid for all renovations (also for single window replacements). For windows ≤ 0.5m², a Ug value of minimum 1.5 W/m²K needs to be fulfilled. For roof window, the legislation foresees that solar control glass must be used (no minimum value is set in the legislation). A shading device alone or in combination with a solar control glass can also be used for roof window with a minimum performance of 0.35 Sw.   

Germany

1.3* 2014
Conditions: Alternatively, to the above mentioned Uw-value also meeting a whole building energy requirement (140% of new building’s primary energy and overall shell transmission coefficient) is possible to meet the requirement. No requirements if less than 10% of the building component area is concerned (building component area for windows consists of: windows, roof windows, window doors and window roofs). Therefore, no requirements exist for single window replacements.

Greece

2.6…3.2* 2010
Climate zone specific requirements exist (A: 3.2, B: 3.0, C: 2.8, D: 2.6). There are no specific requirements for renovated buildings. For deep renovations (>25% of building envelope) however these values apply and the total energy class of the building should comply with Class B (100-75% of primary energy consumption of reference building). Therefore, the requirements do not apply for single window replacements.

Hungary

1.6* 2006
Conditions: In case of a shallow renovation (< 25% of the building shell is replaced) the shown Uw-value of 1.6 W/m²K is valid. Therefore, the requirements apply even if only a single window is replaced. In case of a major renovation the following requirement concerning the specific heat loss coefficient qm ≤ 0,079+0,27*(A/V) is valid since 2017. The existence of air tightness requirements was mentioned but not specified.

Ireland

1.6* 2011
Conditions: For extensions and material change of use, windows, doors and roof lights should have a maximum U-value of 1.6 W/m²K when their combined area is 25% of floor area. The requirements apply even if only a single window is replaced.

Italy

1.7…3.2* 0.35* 2015
Conditions: Climate zone specific requirements exist (2015-2020: A & B: 3.2, C: 2.4, D: 2.1, E: 1.9, F: 1.7; by 2021: A & B: 3.0, C: 2.0, D: 1.8, E: 1.4, F: 1.0). The climate zones are defined as follows: Zone A = up to 600 HDD; Zone B = from 601 to 900 HDD; Zone C = from 901 to 1400 HDD; Zone D = from 1401 to 2100 HDD; Zone E = from 2101 to 3000 HDD; Zone F = more than 3000 HDD). The g-value of 0.35 includes movable shading devices. Additionally, the g-value (=0.35) is only for orientation from East to West, passing through South: there is no limit for North-facing sides. This requirement applies / is enforced solely in case of renovation with a town planning permit. A building permit is needed by exchanging all windows of a property unit.

Latvia

1.3∙k / 1.8∙k* 2015
Conditions: Unorm = normative value / Umax = maximal allowed value. The term “k” is the temperature correction factor (k = 20/(Φi – Φe), where Φi – indoor air temperature and Φe – outdoor air temperature). It is unclear whether the requirements apply also for replacement of single windows.

Lithuania

1.6∙k* 2014
Conditions: The term “k” is the temperature correction factor (k = 20/(Φi – Φe), where Φi – indoor air temperature and Φe – outdoor air temperature). The requirements apply even if only a single window is replaced. If the total area of windows and other transparent building elements exceeds 25 % of total external wall area, the U-value of transparent elements even shall not exceed 1.3 W/(m²K). The existence of air tightness requirements was mentioned but not specified. By 2018 the requirement will change to 1.4∙k.

Luxembourg

1.5* 2016
Conditions: The requirements apply even if only a single window is replaced.

Malta

4.0* 0.89 2015
Conditions: Buildings undergoing major renovation will be required to have a maximum yearly overall energy demand per square metre not exceeding that for the dwelling typology with the highest maximum overall energy demand requirement. Building extensions of 14 m² or less as well as major renovation project, to existing dwellings may be assumed to fulfil all the overall energy requirements (as before) provided that this construction is similar to the un-extended building. Where a building element forming part of the building envelope is being replaced or a building is being extended to a degree which may not be described as a major renovation, the building shall not be required to have a minimum overall energy performance level. Each new element forming part of the building envelope shall however not be exempted from compliance with maximum thermal conductivity requirements for that element. Therefore, the requirements apply even if only a single window is replaced. The U-value requirement only applies when windows and glazed door surface is ≥ 20% of exposed wall.

Netherlands

2.2 2015
Conditions: It is unclear whether the requirements apply also for replacement of single windows.

Poland

1.1* 2017
Conditions: Please note that the value applies to new buildings or replacement when you need a town planning permit. Without such a permit, for window retrofitting, no minimum performance requirement is enforced. Therefore, the requirements do not apply for single window replacements. By 2021 the requirement will change to 0.9 W/m²K. The existence of air tightness requirements was mentioned but not specified.

Portugal

2.2…2.8* 0.10…0.56* 2016
Conditions: This requirement applies / is enforced solely in case of renovation with a town planning permit. There is no need of a permit if only single windows are replaced. Therefore, the requirements do not apply for single window replacements. Climatic zones in Portugal are distinguished by three levels (1, 2 and 3) for winter (I) and also three levels for summer (V) according to the temperature, radiation and altitude. I3 refers to the areas with higher energy needs for heating (heating degrees days for a 18ºC base above 1800) and V3 refers to the areas with higher energy needs for cooling (average temperatures during summer above 22°C). As an example, climatic zone I1V3 refers to a location with mild winters and hot summers. Nevertheless, the heating needs are always significantly more relevant than the cooling needs. Therefore, in many situations the climatic zones are nominated by their winter designation. Concerning the g-value the maximum value for the window system (glass + frame + shading device) is shown. Furthermore, the value depends on the thermal mass of the building.

Romania

1.5* 2016
Conditions: By 2018 the current Uw-value requirement for new buildings (Uw = 1.3 W/m²K) will be enforced for existing buildings. The requirements apply even if only a single window is replaced.

Slovak Republic

1.0 0.60 2016
Conditions: From 2021 onwards stricter requirements are expected. The existence of air tightness requirements was mentioned but not specified. It is unclear whether the requirements apply also for replacement of single windows.

Slovenia

1.3* 0.50 2010
Conditions: In case of metal frames, the requirement is set at 1,6 W/m²K. In spring 2017 an update of the Building Code is planned, that will introduce cost-optimal levels for windows. It is unclear whether the requirements apply also for replacement of single windows.

Spain

2.5…5.7* 2013
Conditions: In Spain the maximum U-value for windows for renovation (when these are replaced, if they are not replaced there is not such a requirement) is the same that for new buildings. In the case that more than 25% of the envelope is renovated, the heating demand should be lower than the reference building (the same building but with an envelope that comply with the previous normative from 2006). The requirements apply even if only a single window is replaced. A combination of building specific requirements (distinction between isolated blocks, terraced houses, block within adjacent buildings, semi-detached house) and climate specific (climate zones are defined as a combination of the severity of winter: α (warmest region: Uw = 5.7 W/m²K), A, B, C, D, E (coldest region, Uw = 2.5 W/m²K) and the severity of the summer (1, 2, 3, 4; mild to extreme)) requirements exist. The existence of air tightness requirements was mentioned but not specified.

Sweden

1.2* 2012
Conditions: The building shall primarily fulfil the energy requirements for new buildings. If not, U-value requirements for the various building parts shall be fulfilled. It is unclear whether the requirements apply also for replacement of single windows.

 

UK – England

1.6* 2016
Conditions: In England either a U-value of 1.6 W/m²K or a Window Energy Rating (WER) of Band C or better is required. The calculation of the WER is set out in the Glass and Glazing Federation (GGF) Guide to the Calculation of Energy Ratings for Windows, Roof Windows and Doors. The requirements apply even if only a single window is replaced.

UK – Wales

1.6* 2014
Conditions: See description of UK-England. Wales follows follows the relevant standards of England’s Building Regulations in their Building Regulation. The requirements apply even if only a single window is replaced.

UK – Northern Ireland

1.6* 2013
Conditions: See description of UK-England. Northern Ireland follows the relevant standards of England’s Building Regulations in their Building Regulation. The requirements apply even if only a single window is replaced.

UK – Scotland

1.6* 2016
Conditions: See description of UK-England. Scotland follows the relevant standards of England’s Building Regulations in their Building Regulation. For extensions to existing dwellings, where the dwelling has poor levels of wall and roof insulation, the requirements are a Uw of 1.4 W/m²K or a Window Energy Rating A. The requirements apply even if only a single window is replaced.

Source: Minimum performance requirements for window replacement in the residential sector, ECOFYS, 2017 and Glass for Europe

 

Extra EU countries

Legal requirements

Uw – value

(W/m²K)

g – value

Last update

 

Norway

0.8 to 1.2

Russia

1.25 to 3.33 N/A 2018
Note: The minimum requirements are set in the national legislation on the thermal performance of buildings (2013). The requirements applying vary depending on the location. Unlike the minimum requirements set in the European Union, the minimum requirements are defined in R-value. The R-value have been converted to Uw values in the table to have comparable data.

Switzerland

1.2

Turkey

2.4

Source: Glass for Europe