2.II.ii. Regulation on individual parts, distinct from whole building performance – OVERVIEW

When renovating (with the exception of major renovations) a building or part of a building in building categories 1 to 12⁵ by means of individual measures, as well as when replacing a component - regardless of its share in the building envelope - maximum heat transfer coefficients (U-values) may be used in conditioned rooms which are determined by one of the two following methods:

a) Before the renewal of a component or before the major renovation of a building or part of a building, a renovation plan must be drawn up, the aim of which is to achieve the requirements for the major renovation of residential or non-residential buildings. Renewed or thermally improved individual components or steps in a major renovation must not contradict such a renovation concept.

b) Such a renovation plan can be omitted if the maximum heat transfer coefficient for components of the (thermal) building envelope has fallen short of the maximum heat treat transfer coefficient for the building by at least 18% (from 1 January 2021 this becomes at least 24%).

The walls, windows and other parts of the building envelope must meet the following U_max/R_min requirements:

Table 3 - U_max/R_min requirements.

A revision of these values with a reinforcement and a homogenisation of the requirement is currently studied and planned for 2021.

In 2015, maximal U-values were added for the insulation of existing walls. These requirements are applicable if the building owner chooses to insulate (in case of a renovation with permit) but do not include any obligations to insulate existing walls.

Table 5. Overview of maximum U-values for renovations since 2006.

The Walloon Region sets several requirements concerning the individual elements of the buildings.

For renovation works, the envelope, walls, window frames, glazings, floors and roofs must have a minimum thermal performance expressed with a U-value [W/m².K]. Since 1 January 2017, the U_max values for windows and floors have been strengthened and, up to now, are identical for the three (3) regions of Belgium.

Every time a window sash or glazing is installed or replaced, the room ventilation must foresee a minimum fresh-air-flow rate.

See Table 1 in section 2.I.ii.

Minimum energy performance requirements are set for the renovated building elements that form part of the building envelope and that have a significant impact on the energy performance of the building envelope. These requirements are specified in Ordinance No. 7 of 2004 on the energy efficiency in buildings, as amended in 2017 (see item 03.06 of KIDs for existing buildings).

Requirements are set for individual elements of buildings and for technical building systems in case of building renovation. When renovating parts of the building envelope, the U-value of the relevant parts shall meet the requirements as prescribed for a new building. The prevention of overheating caused by solar radiation and air permeability of the windows, doors and skylights shall comply with the requirements specified for new buildings. When replacing, modernising or upgrading technical building systems, the same requirements apply as for the installation of these technical building systems in new buildings.

Requirements for building elements had originally been implemented for maximum U-values and only for buildings of more than 1,000 m² that undergo major renovation². Requirements for building elements regardless of renovation were set in 2013⁴. These requirements set maximum U-values for roofs, walls and windows that were replaced or retrofitted or were part of an extension to an existing building. In 2016, these requirements were revised, and as of 1 January 2017 new, more stringent U-values are required for envelope building elements installed in existing buildings⁵. The new requirements that will be set in force in 2020 will require lower U-values only for windows.

The Energy Management Act sets an obligation in the case of improvements other than major renovations of either an existing building or a completed one, during which the requirement to improve the energy performance must be achieved for the altered structural elements of the building envelope or technical building systems. If improvements to individual parts are performed within ten (10) years from issuing the EPC of the building, the building owner or association of unit owners are obliged to comply with the energy performance requirements for buildings set in Decree No. 264/2020 Coll., and the construction must meet the energy performance requirements for either the altered structural elements of the building envelope or the altered technical building systems, also set in Decree No. 264/2020 Coll. This must be proved in the building's records relating to an altered structural element of the building envelope or an altered technical system, and the owner must keep these records for five (5) years.

Table 6: Reference parameters and values for altered building technical systems.

The BR2015 tightened the energy performance requirements for individual building components for all building types. This applies to the replacement of components and to major renovations. In case of renovations, measures must be economically and technically feasible, i.e., they must have a simple payback time of less than 75% of their expected lifetime as defined in the Danish Building Regulations. In case of the full replacement of a component (e.g., a new roof, new window, new outer wall), the new component must meet the requirements set in the BR2018, regardless of profitability.

_{Note: Minimum requirements are primarily set to eliminate the risk of surface condensation and hence mould growth. Applies for both new and existing buildings being renovated.}

Table 2. U-values and thermal bridges requirements for existing buildings – examples.

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There are no requirements on individual building parts.

The Finnish National Building Code states that, when the technical systems of any type of existing buildings are renovated, modernised, or replaced, the following requirements must be met:

1. The minimum annual efficiency of heat recovery must be at least 45%.
2. The maximum specific fan power (SFP) of a mechanical supply and exhaust system is 2.0 kW/(m³/s).
3. The maximum specific fan power (SFP) of a mechanical exhaust air system is 1.0 kW/(m³/s).
4. The maximum specific fan power (SFP) of an AC system is 2.5 kW/(m³/s).
5. The efficiency of heating systems must be improved where possible when the related equipment and systems are renewed. After renewal, the ratio between efficiencies of the building's main heating system and the main heat distribution system must be at least 0.8. The ratio is the quotient of the annual efficiencies of the heating system and heat distribution system. This is to ensure that the overall heating efficiency is improved.

There are also requirements set for other technical systems, e.g., for different temperature levels of Domestic Hot Water (DHW) systems or for apartment-specific water meters.

As previously described, there are two regulations for existing buildings. The appropriate regulation to be implemented is determined by the building size and the extent of the renovation (see Figure 1, where the Regulation by Building Component is based on minimum requirements for the different components of the building (envelope and systems)). Table 2 shows current and future maximum U-values for envelope elements.

These two regulations have some rules in common, especially regarding domestic hot water, setting maximum heat loss depending on the boiler size, and giving European Norms 89 and 26 as a reference for some systems’ performance.

The Regulation by Building Component sets a minimum efficiency around 90% for boilers of more than 400 kWh of thermic power and a coefficient of performance of 3.2 for heat pumps on heating mode. For AC units below 12 kW, the energy efficiency rating should be at least 3.0. For other AC systems, the efficiency should be between 2.6 and 3.0. Ventilation unit consumption should not exceed 0.25 Wh/m³ for residential buildings, and 0.3 Wh/m³ for non-residential buildings. These requirements are set for systems with nominal power not covered by the Ecodesign Directive 2009/125/EC.

Table 2. Current and future maximum U-values for envelope elements in the Regulation by Building Components.

Several requirements address the performance of individual building parts in existing buildings. Table 4 shows the regulations on individual building parts concerning their first instalment, replacement or renewal.

Table 4. Regulations on individual building parts concerning their first instalment, replacement or renewal.

The KENAK has set minimum requirements (maximum U-values) for the building elements, as well as for energy losses and gains for the whole building envelope (max. U_building), and minimum requirements for the efficiency of heating, cooling and hot water production systems. These are set for all building uses, supplemented with lighting requirements for the tertiary sector buildings.

The regulations include requirements on technical building systems elements (e.g., on balancing, control, pumps, airtightness of ventilation ducts, boilers, performance of the heat recovery system, energy use of fans, passive shading systems). The rulebook does not set any direct system performance requirements; only the upper threshold of the total primary energy consumption of the building is defined.

The requirements of the ErP directive on gas boilers, water tanks, heat pumps, pumps, ventilations systems, etc., have a much more significant impact on the construction sector than element requirements set in the rulebook.

For existing dwellings (residential) acceptable levels of thermal insulation for each of the plane elements of the building are specified in terms of average area-weighted U-value (Um) for material alterations and material changes of use, as specified in column 2, Table 11. These values can be relaxed for individual elements or parts of elements where considered necessary for design or construction reasons. Maximum acceptable values for such elements or parts of elements are specified in column 3, Table 11. Where this relaxation is availed of, the average area-weighted values given in Table 11 continue to apply and compensatory insulation measures may be necessary for other elements or parts of elements of that type to ensure that these are met. Where there is underfloor heating, the maximum floor U-value should be 0.15 W/m².K.

Table 11: Maximum elemental U-value for material alterations or material change of use for residential buildings, 2019.

In case of second-level major renovations and minor renovations, specific requirements on building components are requested, as explained in 2.II.i.

The following specific requirements on buildings parts also apply:

• In case of new windows (except on the north façade), the total solar transmission factor (ggl+sh) shall be lower than 0.35;
• In case of refurbishment of external structures, it is requested to verify the risk of critical surface humidity and interstitial condensation according to EN ISO 13788;
• In case of refurbishment of the roof, it is requested to verify the techno-economic feasibility to adopt technical solutions (cool roof, ventilated roof, green roof) to reduce the energy need for cooling.

Design requirements concern a minimum permissible level of the energy performance of buildings, requirements for the heating system (Regulation No. 383), and envelope values (LBN – 002-15). Projecting requirements for domestic hot water, cooling, ventilation and lighting systems are based on construction laws and the related building codes, with references to applicable standards. The projecting requirement for the primary energy level is set for NZEB only.

Requirements for technical building systems and building envelope elements are set in multiple regulations^2,3,9 concerning the respective buildings or technical elements.

These regulations cover gas-, wood- and oil-fired boilers, AC systems, heat pumps, ventilation systems and components of the building envelope. The Ministry of the Environment, Climate and Sustainable Development and the Ministry of Energy and Spatial Planning share the responsibility with respect to these areas.

Every new individual building element has to fulfil minimum requirements defined in these regulations.

Furthermore, large installations must comply with certain requirements set by the environmental and safety impact authorisation procedure¹⁰; such requirements depend on the scale and type of the installation. They can be grouped into general security requirements, technical requirements and energy performance requirements (according to the best available technology).

Minimum energy performance requirements for elements of the building envelope first came into force in 2007 and were amended when the updated minimum requirements came into force in 2016. The levels of performance in the updated requirements were shifted from being based on a traditional building trade system to being based on the results of the cost-optimal studies.

The second set of cost-optimal studies includes a detailed analysis of each building element to give guidance for the update of minimum requirements if these are required.

Requirements for building elements include those for the passage of heat for all building elements in all parts of the building envelope as well as elements dividing an internal area from an unconditioned space, such as the stairwell of an apartment building. For façades subject to solar gain, detailed provisions are also in place to prevent overheating.

The second set of cost-optimal studies have explored the cost-optimal U-value of building elements for the vast array of reference buildings. Gaps between the current minimum requirements and the cost-optimal level were identified in a number of reference buildings. Interestingly, the results varied according to building use and typology.

This exercise has been carried out to reflect any changes within the cost-optimal levels due to changes in parameters such as cost, energy price and development of new technologies since the first studies. Studies have also been useful to give insight into which are the most cost-effective systems to be used for reaching NZEB levels and beyond.

See Tables 2 and 3 in section 2.I.ii.

For residential buildings, one option is to meet the requirements at the component level, whereas for non-residential buildings the requirements apply to the building as a whole. The local authorities can give exemptions from the requirements under certain conditions. This applies to necessary remodelling, renovation and change of use, and in cases when, for example, the requirements will be unreasonable compared to the energy savings the measures will provide. Still, constructors will have to build as energy efficiently as economically and technically feasible.

Article 1 of the regulations on technical requirements for building works specifies that minimum requirements for renovation of existing buildings are fulfilled when walls and technical building systems comply with the requirements for thermal insulation specified in Annex 2 of the regulation, and the window thermal characteristics comply with the requirements specified in §2.1 of Annex 2 (section 2.I. -Tables 1 - 5).

An improvement seen is the stepped requirements (2013 level, 2016 level) that are applicable to building components. Technical buildings systems are, without exception, covered by these improvements, and the minimum efficiency of equipment is now higher than it was in 2013.

Existing residential buildings are only obliged to comply with these stricter requirements when they undergo renovations. The building component to be renovated must adhere to the minimum performance levels defined in the regulation.

Ministerial Decree 324/2016 sets the methodology for evaluating individual parts of buildings (building units/apartments). It allows for classifying an individual part of the building according to the evaluation results as five different levels of construction in accordance with the scale adopted for the entire building (low-energy, ultra-low-energy and nearly zero energy). The assessment is performed for individual building structures of the building envelope, taking into account the position of an individual part in the building, and compares it with the requirements for envelope building elements according to STN 73 0430-2 + ​​Z1 + Z2: 2019.

Requirements for the evaluation of the heating system are set for individual levels of construction, depending on the method of the control system and hydraulic balancing of the system (Table 2). The evaluation of the DHW system is performed according to the type of batteries and the distance between the DHW supply shut-off valve and the farthest battery, as well as by comparing the actual and required thermal insulation thickness of DHW distributions in the individual part of the building. For example, an individual part of the building meets the requirements for nearly zero energy if there is a smart control system of the heating system installed and DHW distributions are insulated using thermal insulation with a thickness over the diameter of the pipe.

Table 2. Evaluation of the building part heating system.

The introduction of system performance minimum requirements is being considered in the revision of the building codes PURES, planned for late 2021. The amendment is related to the introduction of the new set of CEN EPBD standards.

Currently (in PURES 2010), system energy efficiency is achieved by selecting products that fulfil the energy efficiency requirements, with corresponding design and construction rules for sub-systems. The regulation has imposed system performance requirements via many rules on product and sub-system energy efficiency. The rules address heating, ventilation, cooling, AC and lighting sub-systems and the energy efficiency of products.

The analysis of the performance of thermal generation systems in Spain is carried out through the Regulation of Thermal Installations of buildings. One of the main aspects that has been improved in recent years, and that is helping to renovate the thermal generation systems, is the PAREER¹ support line.

This programme has a specific section that encourages the replacement of thermal generation systems with more efficient ones, with aid of up to 30% for large-scale replacements. This aid has proved to be effective due to the high volume of applications received in recent years.

The evaluation mechanism to check the effectiveness of this aid programme is based on the energy rating; to qualify for aid, it is necessary to improve the energy performance rating of the building by at least one energy class. Therefore, it has a dual benefit: it encourages energy performance certification beyond sale and rental purposes, while at the same time encouraging the revitalisation of the sector, with the replacement of high-performance systems in thermal generation.

Energy requirements apply to existing buildings only in the event of a change. A modification of a building shall not impair energy efficiency, unless there are exceptional reasons, or if the building nevertheless meets the energy requirements applicable to new buildings.

If the altered building, for special reasons, cannot meet the energy performance requirements for new buildings, the changes in the building’s envelope shall strive to ensure U-values, see Table 4. 

Table 4. U-values to aim for (Table 9:92, BBR 29).

As per new buildings. See details above.

See England report for details.

An approach similar to England has been adopted. Where a part of a building is to be renovated the Building Regulations will apply. In most cases (other than straightforward replacement or installation of a fitting or control) a full plans application or notice of work will be required. Standards for work to existing buildings are provided for in Section 3 of the relevant Technical Booklet F1 or F2^7 8. 

An approach similar to England was adopted. See England report and Scottish Technical Handbooks^2 3 for details. The Technical Handbooks reference industry guidance, e.g. the Chartered Institution of Building Services Engineers (CIBSE) Commissioning Codes²², and the Building Services Research and Information Association (BSRIA) Commissioning Guides²³.