2.I.iv. Requirements for building components for new buildings – OVERVIEW

The maximum U-values for building components are set by the OIB Guideline 6. They apply for new residential and non-residential buildings (Table 8).

Table 8. A selection of U-values of the OIB Guideline 6.

Furthermore, OIB Guideline 6 requires that energy systems of buildings must consider and demonstrate the technological, ecological and economic feasibility of high-efficient systems. In this context, new apartment buildings with more than three (3) building units must have central heating systems (specific exceptions are allowed), and ventilation systems must be equipped with a heat recovery system.

Requirements for building components are the same for new buildings as for renovations. Walls, windows and other parts of the building envelope must meet U_max/R_min requirements, which are listed in Table 3.

However, in order to meet the envelope global performance requirements, the maximum mean U-value for the opaque wall is around 0.12 W/m².K and the maximum mean U-value for windows is around 1 W/m².K. Moreover, a good sealing of the building is also required to achieve envelope performance requirements with an airtightness around 1.5 m³/h.m². This is not an obligation but is a consequence of the net heating demand requirement for new residential units.

Since 2006, maximal U-values have been in place for new building components. The levels were systematically strengthened over the years and are meeting current cost-optimal levels (Table 3).

Table 3. Overview of the maximum U-values for new buildings since 2006.

As mentioned in Table 1 of section 2.I.ii., there are requirements relating to each element of the building envelope defining the protected building volume (U_max). In addition, requirements are also prescribed for the hygienic ventilation rates of the building.

Minimum energy performance requirements are set for the design of new buildings and 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 buildings as a whole;
• for the U-values of the building envelope elements;
• for the reduction of the effects of thermal bridges and water vapour condensation inside building elements and on the surface of building elements;
• on the efficiency of technical building systems.

Since 2015, in addition to the previously determined U-values for building envelope elements, U-values are also prescribed for cupolas, light bars and windshields.

The designed and installed heating systems in new buildings must compensate for heat losses in order to maintain indoor thermal comfort. Among other requirements, heating systems must have thermally insulated pipework.

For buildings equipped with heating systems with air-to-air heat pumps, the seasonal coefficient of the performance of individual heat pumps (SCOP) should be ≥ 4.0. SCOP includes the heat pump, regulation, auxiliary heating unit and other parts of the system, such as pumps and ventilators on the side of the heat storage tank.

For heating systems with air-to-water, water-to-water and soil-to-water heat pumps, the seasonal performance factor (SPF H3) of individual heat pumps should be ≥ 3.0. SPF H3 is the factor which influences the calculated limit that includes the heat pump, regulation, auxiliary heater, and all parts of the system, including pumps and fans on the side of the tank's thermal sources (air, water, soil). Air-to-air systems do not contain the listed parts (they contain freon) and have no impact on the factor.

Since the implementation of the EPBD in Cyprus, emphasis was given on improving the building envelope of new buildings. Thus, maximum U-values were established for roofs, walls, windows and floors in contact with the external environment. These U-values have, gradually but drastically, been tightened over the last twelve (12) years, in an attempt to reduce energy demand for heating and cooling in new buildings. Furthermore, the introduction in 2013, of a maximum shading factor for windows was the first minimum requirement purely set to address cooling energy demand. The implementation of NZEB requirements in 2020 does not have any significant impact on the U-values. However, new maximum primary energy consumption and maximum heating demand for residential buildings are expected to push building designers to examine even lower U-values.

Any new building must comply with the energy performance requirements of the Energy Management Act, which includes minimum energy efficiency requirements of technical building systems and requirements for the building constructions (see Table 1). These minimum values are defined in Annex 1 of Decree 264/2020 applied to the reference building. The amendment of Decree No. 78/2013 to Decree No. 264/2020 Coll. introduced stricter reference values for some technical building systems. In case of heating, the overall efficiency of the heating system in the reference building has increased from a very low level of about 54% to a new level of about 73%. This value better reflects the real heating situation.

Table 4. Example of requirements for new or changed building systems.

Individual building elements must be insulated to a level ensuring that the heat losses through them do not exceed the values included in Table 1:

Table 1: Maximum U-values and linear losses.

Additionally, the energy balance of windows and glazed outer walls must not be less than -17 kWh/m²/year (equal to a B-label window in the voluntary Danish window labelling scheme). The energy balance through roof lights and glazed roofs must not be less than 0.0 kWh/m² per year. The energy balance is calculated for a standard sized window with standardised outdoor conditions.

Additionally, new buildings must be designed and constructed so that the design transmission loss per m² heated gross floor area does not exceed 12.0 + 6.0/E + 300/A (voluntary low-energy class: 11.0 + 6.0/E + 300/A), where E represents the number of floors and A the heated floor area. The number of floors is a decimal number, which is calculated as heated floor area divided by the built-up area (the building's vertical projection on the ground in case of split-levels). Design temperatures are defined in Danish Standard DS 418:2011. Buildings with an average room height above 4.0 metres receive a supplement of 1.0 W/m² per metre. A heated basement, which is not part of the floor area, is only partly included in the calculation.

Non-residential buildings can get an addendum in the energy framework due to special use conditions in the building. The special conditions and standard values are listed below. The extension is calculated as a difference between a standard calculation and a calculation using actual values.

• Common lighting level above 300 lux;
• Ventilation rate above 1.2 l/sec per m² heated floor area;
• in-use hours during the heating season to meet the atmospheric indoor climate;
• Domestic hot water consumption above 100 l per m² heated gross floor area per year;
• Weekly usage hours above 45 hours per week;
• Ceiling height above 4.0 m.

Estonia has set requirements for building envelopes to be sufficiently airtight and insulated. In the determination of the suitable insulation for the building, different factors must be taken into consideration. Key factors are minimum energy performance requirements, need for maintenance, thermal comfort and the avoidance of condensation and mold growth on thermal bridges, inner surfaces, and structural elements.

In order to maintain a comfortable thermal environment in the building, the overall thermal transmittance of its envelope in general may not exceed 0.65 W/(m²K). If the doors or windows have a thermal transmittance value higher than 0.65 W/(m²K), thermal comfort must be ensured with a heating system solution.

The average leakage rate of the building envelope may not exceed the value used in the energy calculation performed to prove the building’s compliance with the minimum requirements for energy performance.

The requirements for systems and/or building components for new buildings are given in the building code that is based on regulations given by the Ministry of the Environment. The building code defines requirements for heat losses, summertime temperatures, specific fan power (SFP) of ventilation and AC as well as for energy consumption metering. Details are shown in Table 1.

For residential buildings (single-family homes, row houses and apartment buildings) it is alternately possible to show compliance with the building code (energy performance of the building) using the structural energy efficiency method in which the building must adhere to set values for structural energy efficiency (U-values), maximum heat losses as well as the efficiency of the technical systems. The method limits the use of heating sources to district heating, ground source heat pumps or air-to-water heat pumps. The information must be ascertained with documentation.

As explained before, the thermal regulation for new buildings sets general performance objectives. Therefore, it does not include any requirements on systems efficiency nor on building components. However, the requirements on B_bio entail a minimum performance of the envelope, which is different for every construction project. Indeed, B_bio is a modulated combination of the energy needs of the envelope for heating, cooling and lighting.

The overall performance requirement (non-renewable primary energy demand) is accompanied by a requirement that limits the overall specific heat transmission coefficient¹⁷. This requirement can turn out to be the main efficiency requirement in buildings where the energy is provided mainly by RES.

The heating and cooling demand of new buildings and of public buildings undergoing major renovations must be at least partially covered by systems that use RES. There are specific percentages given for the different RES-based systems, which can be combined which each other. The use of RES can be substituted by the use of waste heat (subject to certain conditions), district heating or cooling (subject to certain conditions), the installation of a combined heat and power system or cooling (subject to certain conditions) or with an energy performance of at least 15% better than the required performance (substitute measures).

The in July 2017 revised KENAK introduced stricter minimum energy performance requirements regarding new buildings’ components and whole buildings’ envelope. The requirements for existing buildings remained the same. Energy requirements for new buildings are presented in Table 1. Maximum acceptable thermal transmittance values for the building envelope of new buildings are presented in Table 2, according to the 4 climatic zones of Greece (Figure 1).

Table 1. Minimum energy performance requirements for building components of new buildings.

Table 2. Maximum acceptable mean U-value of the building envelope (U_m) for new buildings.

Figure 1. The 4 climatic zones of Greece.

Some features newly introduced in the revised regulation are the following:

• The concept of a low-demand building, regarding the DHW needs, introduced the   DHW recirculation using a pump (the use of a speed-adjustable speed pump is required, with a constant Δp).
• The concept of terminal control through space thermostats and thermostatic valves per operating space. Also, the obligation to use calorimetry is stated, where there is a need for cost allocation.
• The concept of minimum lighting efficiency (60 lm/W) for tertiary sector buildings, as well as the requirement to control the lighting with separate switches.
• Two new paragraphs are introduced concerning the technical building systems:
  • The degree of automation, predicted depending on the surface and use of the building.
  • The requirement for each individual technical building element, to comply with the requirements of the EU Eco-design and ecolabel Directives.

In November 2017 (M.D. DEPEA/oik.182365, GoG B’ 4003/17.11.2017), the technical guidelines were updated following the final results from the cost-optimal study, and new energy performance requirements were endorsed for both the building components and the technical building systems for heating, cooling and ventilation.

The format of the EPC has changed (Figure 2) and provides information not only about the current energy category of the building/building unit, but also about the potential energy category reached according to the first energy efficiency recommendation. Also, data regarding the final energy consumption according to energy fuel and use are presented. Finally, the expiry date of the certificate is stated.

Figure 2. The building EPC format.

Table 3. Maximum U values (W/m²K) of building elements, cost-optimal and NZEB levels.

The requirements for building components in new buildings are described in the Technical Guidance Document Part L accompanying the Building Regulations. There is a separate Technical Guidance Document for dwellings (residential) and buildings other than dwellings (non-residential). Where a building contains dwellings, e.g. apartments, Technical Guidance Document Part L should be used for the individual dwellings. The Technical Guidance Document Part L for Buildings other than Dwellings should be used for those parts of the building which are not a dwelling such as common areas and, in the case of mixed-use developments, the commercial or retail space.

The overall energy, carbon and RES energy performance levels specified in the Building Regulations and Technical Guidance Documents Part L are in the nature of backstop minimum performance levels so as to ensure reasonable levels of performance for all factors affecting energy use, irrespective of the measures incorporated to achieve compliance.

Meeting the specified individual minimum performance levels will not necessarily mean that the overall level specified for primary energy consumption and related CO₂ emissions will be met. One or more of the following performance levels specified, will need to be exceeded to achieve this: use of RES, fabric insulation, airtightness, boiler efficiency, building services controls, insulation of pipes, ducts and vessels, and mechanical ventilation systems.

Table 7: Maximum Element U-Values (W/m²K) for residential buildings 2019.

Table 8: Minimum energy efficiency standards for boiler systems in non-residential buildings, 2017.

In addition to the aforementioned requirements for the whole building performance, the following energy requirements for system and building components shall be verified¹⁰:

• The mean transmission heat transfer coefficient, H’_T [W/m²K], is lower than the limit value for the given climatic zone and surface-area-to-volume ratio (S/V) of the building (Table 4);
• The ratio of summer effective collecting areas of the transparent components (A_sol,est ) to the net floor area (A_{sup util}) is lower than the limit value defined for residential and non-residential buildings (Table 5);
• The mean efficiencies of the technical building systems for heating (ηH), cooling (ηC) and domestic hot water (ηC) are higher than those calculated for the reference building;
• The mass of the external walls (except northeast to northwest) is larger than 230 kg/m² or, alternatively, their periodic thermal transmittance YIE (as defined in EN ISO 13786) is lower than 0.12 W/m²K;
• The periodic thermal transmittance YIE of roofs and floors is lower than 0.18 W/m²K;
• The U-value of the inter-building opaque components (floors and walls) is lower than 0.80 W/m²K (Table 2).

Table 4. H'_T maximum limit value.

Table 5. A_sol,est/A_sup,utile maximum limit value.

Design requirements for heating systems concern the minimum permissible level of the energy performance of buildings (Regulation No. 383) and for the envelope values (LBN – 002-15). Design requirements for hot water, cooling, ventilation and lighting systems are based on construction laws and the related building codes, with references to applicable standards. The design requirements for the primary energy level are set for NZEB only. Changes for the requirements of the building envelopes for residential buildings are shown in Table 4 and Figure 1.

Table 4. Changes for the requirements of the building envelopes for residential buildings.

Figure 1. Changes for the requirements of the building envelopes for residential buildings.

Requirements for technical building systems are set in different regulations covering gas-, wood- and oil-fired boilers, AC systems, heat pumps and ventilation systems.

Some decades ago, Luxembourg established a mandatory technical acceptance procedure for new oil- and gas-fired boilers as well as regular inspections of these boilers in existing buildings. Newly installed boilers need to be technically accepted before they can be used (acceptance procedure). However, an operator is not obliged to get an authorisation in order to be allowed to install a boiler (approval procedure). For wood-fired boilers this system became mandatory in 2014. The acceptance procedure and the regular inspection of AC systems have been mandatory since 2009 in residential as well as non-residential buildings. The acceptance procedure checks the conformity of the security equipment, the location, the smoke exhaust and the combustion quality and efficiency. Dimensioning is not checked at this stage but is done so during the periodic inspection. Since Luxembourg imports nearly all appliances and equipment, European standards as well as standards valid in the import countries are also applicable in Luxembourg.

RGD 2007 and RGD 2010 set energy performance requirements concerning building envelope elements, pipework insulation, ventilation and AC systems.

A set of minimum energy performance requirements for buildings and building services entered into force on 1 January 2016 with the ratification of Legal Notice 434 of 2015. These requirements are officially referred to as Technical Document F, Part 1: Minimum Energy Performance Requirements for Buildings in Malta, and Technical Document F, Part 2: Minimum Energy Performance Requirements for Building Services in Malta.

Elements forming part of the building envelope are required to conform to provisions for the conservation of heat during winter as well as requirements to prevent overheating in summer. The requirements for thermal transmittance were tightened with the introduction of the latest minimum energy performance requirements referred to above.

Requirements to prevent overheating include limitations to the maximum allowed glazing area, stipulated according to the orientation of the façades. An alternative compliance system is present that gives the designer a certain degree of flexibility. This involves the calculation of overheating within the space by means of dynamic simulations together with the ability to factor in shading and other measures to prevent overheating.

Until 10 March 2020, there were no requirements in the Netherlands for new buildings for separate energy efficiency measures for technical building systems and products concerning space heating, hot water, air-conditioning or large ventilation systems. Instead, the total building had to reach a level of efficiency, indicated by the energy performance coefficient. This way, builders and developers were given the freedom to choose the most cost-efficient solution as regards the envelope and the technical building system of that particular building.

As of 10 March 2020, system requirements have come into force for systems concerning space heating, space cooling, ventilation, hot tap water and built-in lighting. The system requirements apply if a new system is installed or an existing system is changed.

The energy performance requirements that apply to technical building systems are expressed in the calculated primary fossil energy in relation to the net need (Table 5). This not only values the efficiency of a technical building system, but also the use of renewable energy. A digital calculation tool has been developed for this⁶.

Table 5. Requirements for the system efficiency of technical building systems (effective as of 10 March 2020, source: RVO)

The mandatory minimum requirements for building elements in new buildings are presented in Table 2.

All building components are included in the calculation of energy performance, which is regulated in the building code (see 2.1.i. Minimum requirements):

• Exterior wall U-value ≤ 0,22 W/m²K
• Roof U-value ≤ 0,18 W/m²K
• Exposed floors U-value ≤ 0,18 W/m²K
• Window/door U-value ≤ 1,2 W/m²K
• Minimum airtightness (Max air changes/hour at 50 Pa pressure difference) 1.5

Pipes, ducts and equipment used for the building´s heating system must be insulated. The thickness of the thermal insulation must be cost-optimal and calculated according to a European standard, e.g., the EN 12828:2012+A1:2014 or the DS 452:2013.

A detailed description of the current regulations for new buildings is given in the CA EPBD Book 2016 country report of Poland.

According to the regulation on the technical conditions that new buildings must meet, the main requirements include:

• maximum values of thermal transmittance of individual elements of the building envelope: walls, roofs, floors, windows, doors and other types of partitions;
• recommended airtightness of envelope and threshold values for the air leakage of windows and balcony doors;
• the maximum area of transparent parts of the building envelope with a thermal transmittance ≥ 0.9 W/m².K;

Since 2014, new buildings must comply with stricter requirements⁶, imposed by the roadmap defined in the national regulation². This roadmap was set with the goal of having all new buildings as NZEB by 2020; thus, a tightening of the requirements was planned via a stepped enforcement (2013, 2016).

The requirements are focused on U-values for walls, roofs, pavements, and windows, as well as the solar factor (g-value) and shading when looking at building components. When it comes to technical building systems, the requirements are focused on the minimum efficiency of equipment (water heater, heat pumps, boilers, etc.) and also on the minimum RES contribution, specifically solar thermal collectors. Additional requirements exist for air exchange rates and minimum indoor air quality.

The evolution of requirements for the building envelope, as well as for ventilation and RES in residential buildings is shown in Table 2.

Table 2: Minimum requirements evolution for residential buildings, envelope, ventilation and RES.

Table 3 shows the evolution of requirements for technical building systems in residential buildings.

Table 3: Minimum requirements for technical systems.

Building components for new buildings should correspond to the requirements set by national standard STN 73 0540-2+Z1+Z2:2019 for the building envelope, with separate values for external walls, roofs, windows and dividing structures between heated and unheated spaces. The revised standard (Z1), which came into force on 1 August 2016, and the consolidated standard, which came in force on 1 July 2019, are setting the gradually tightened requirements (Table 1).

Table 1. Requirements for the U-value of selected building envelope structures.

Current minimum requirements for systems and building components are defined in PURES 2010 regulations, with the revision of the regulation planned for publication by late 2021.

The study on PURES revisions (2015/2016) recommended complementing the minimum efficiency requirements of technical building systems with specific values for space heaters, combination heaters, packages of space heaters, temperature controls, solar devices and packages of combination heaters, as well as water heaters, hot water storage tanks and packages of water heaters and solar devices based on the requirements of the Eco design Directive and delegated regulations No 811/2013 and No 812/2013.

Based on the cost-optimal study, more stringent minimum requirements were proposed for building components (Table 3). However, the designers should optimise the U-values of the envelope elements in order to ensure that the design specific transmission heat transfer coefficient (HT’) remains below the minimum value, as presented in Figure 3, and to comply with energy performance-based minimum requirements. Linear thermal bridges should be kept below Ψe = 0.2 W/(mK).

Figure 3. Maximum allowed specific heat transfer coefficient by transmission, development of regulation from 2002 to 2010 and proposal in compliance with cost-optimal study.

Table 2. Minimum requirements for the elements of the building envelope; current status (2020) and proposal for revised regulation expected in late 2021.

The energy performance requirements for heating, cooling and domestic hot water generation systems are regulated in Spain through the Regulation of Thermal Installations of Buildings (RITE), and those for lighting in non-residential buildings through the CTE.

www.boe.es/boe/dias/2007/08/29/pdfs/A35931-35984.pdf

The RITE is a technical document of a regulatory nature; therefore, it is mandatory to obtain installation permits for the use of thermal energy systems. It regulates, among others, the following aspects:

• requirements for the correct dimensioning and assembly of thermal systems;

• minimum performance of heat generating systems, cooling and domestic hot water;

• the mechanism and periodicity of safety and energy performance inspections.

This document was updated and published in 2013 through Royal Decree 238/2013, and a new update is planned in five (5) years’ time.

Sweden uses functional, rather than detailed, requirements. This means that the developers are free to choose which areas they will focus their efforts on. As a result, there are no qualitative figures on specific building components. The requirements, however, include criteria that focus on building components: the average thermal transmittance (U_m) of the building envelope (A_om).

As long as the verified primary energy number (EP_pet), as well as the Um-value (and the installed electrical power for heating), is lower than the requirements, see Table 2, the building is regarded as compliant.

Small stand-alone buildings < 50 m² are exempted from energy performance requirements. Thus, only requirements for average U-values and airtightness apply to small buildings.

Please refer to Section 2.I.i. Progress and current status of new buildings for details on building fabric requirements for new buildings.

Please refer to Section 2.I.i. Progress and current status of new buildings for details on building fabric requirements for new buildings.

Building components are expected to conform to relevant standards for materials and workmanship controlled under Part B (Materials and workmanship) of Northern Ireland’s Building Regulations¹⁴. In terms of energy performance requirements under Part F (Conservation of fuel and power), components for new buildings must form part of the overall building performance assessment, with minimum limiting U-value standards for each component providing an absolute backstop position.

Please refer to Section 2.I.i: Progress and current status of new buildings, for further details on criterion 2 which outlines the minimum acceptable standards for fabric, air permeability, and building services efficiencies requirements as per the relevant Technical Booklets.

Please refer to Section 2.I.ii. Format of national transposition and implementation of existing regulations for details on requirements for new buildings.

Additional guidance¹⁷ is also published to assist in the understanding of the principles of heat loss¹⁸, to limit thermal bypass at junctions, and on provisions for airtightness testing¹⁹ of new buildings.