Limitation of Primary Energy Use and CO2 Emissions
This Section provides guidance on how to show compliance with the requirements in relation to primary energy consumption and CO2 emissions specified in Regulation 8(a) of the European Union (Energy Performance of Building) Regulations 2019. The methodology for calculation to be used is specified in the Regulation as the DEAP methodology.
This methodology is published by the Sustainable Energy Authority of Ireland (SEAI) and calculates the energy consumption and CO2 emissions associated with a standardised use of a dwelling and standardised external environmental conditions.
The energy consumption is expressed in terms of kilowatt hours per square metre floor area per year (kWh/m2 /yr) and the CO2 emissions expressed in terms of kilograms of CO2 per square metre floor area per year (kg CO2/m2 /yr). Full details of the methodology are available on the SEAI website at http://www.seai.ie. The DEAP manual, also available on that website, describes the DEAP methodology.
The calculation is based on the energy balance taking into account a range of factors that contribute to annual energy usage and associated CO2 emissions for the provision of space heating, cooling, water heating, ventilation and lighting of a dwelling.
These factors include:
size, geometry and exposure of the dwelling;
materials used for construction of the dwelling;
thermal insulation of the different elements of the building fabric;
ventilation characteristics of the dwelling and ventilation equipment;
efficiency, responsiveness and control characteristics of the heating system(s);
solar gains through glazed openings of the dwelling;
thermal storage (mass) capacity of the dwelling;
the fuel used to provide space and water heating, ventilation and lighting;
renewable and alternative energy generation technologies incorporated in the dwelling;
air permeability of the dwelling.
The performance criteria are based on the relative values of the calculated primary energy consumption and CO2 emissions of a dwelling being assessed, and similar calculated values for a reference dwelling. Details of the reference dwelling are given in Appendix C.
The criteria are determined as follows:
primary energy consumption and CO2 emissions for both the proposed dwelling and the reference dwelling are calculated using DEAP.
the calculated primary energy consumption of the proposed dwelling is divided by that of the reference dwelling, the result being the energy performance coefficient (EPC) of the proposed dwelling. To demonstrate that an acceptable primary energy consumption rate has been achieved, the calculated EPC of the dwelling being assessed should be no greater than the Maximum Permitted Energy Performance Coefficient (MPEPC). The MPEPC is 0.3. This coefficient represents the numerical indicator for the energy performance of Nearly Zero Energy Dwellings.
the calculated CO2 emission rate of the proposed dwelling is divided by that of the reference dwelling, the result being the carbon performance coefficient (CPC) of the proposed dwelling. To demonstrate that an acceptable CO2 emission rate has been achieved, the calculated CPC of the dwelling being assessed should be no greater than the Maximum Permitted Carbon Performance Coefficient (MPCPC).
The MPCPC is 0.35. This coefficient represents the numerical indicator for the CO2 emission rate for Nearly Zero Energy Dwellings.
The DEAP software will calculatethe EPC and CPC of the dwelling being assessed and clearly indicate whether compliance with the requirements of Regulation 8(a) has been achieved.
Where a building contains more than one dwelling (such as in a terrace of houses or a block of apartments), reasonable provision would be to show that:
every individual dwelling has an EPC and CPC no greater than the MPEPC and MPCPC respectively; or
the average EPC and CPC for all dwellings in the building is no greater than the MPEPC and MPCPC respectively.
Where the latter approach is used, the average EPC and CPC are calculated by multiplying the EPC and CPC for each individual dwelling by the floor area of that dwelling, adding together and dividing the results by the sum of the floor areas of all dwellings. Common areas in the building are not included in this calculation.
The requirements that the calculated EPC and CPC do not exceed the calculated MPEPC and MPCPC respectively, applies to the constructed dwelling. It is considered good practice for designers to calculate the EPC and CPC at early design stage in order to ensure that the requirements can be achieved by the constructed building.
It is also open to professional bodies or other industry interests to develop model dwelling designs that can confidently be adopted without the need to calculate the EPC and CPC at design stage.
However, the use of constructions and service systems which have been assessed at design stage, or other model designs, does not preclude the need to verify compliance by calculating the EPC and CPC when all relevant details of the final construction are known.
The use of renewable and low carbon technologies, such as solar hot water, biomass (e.g. wood and wood pellets) and heat pumps, whether provided to meet the requirements of this Part of the Building Regulations (see Section 1.2) or provided as additional to meeting that requirement, can facilitate compliance with the requirements in relation to primary energy use and CO2 emissions.
As defined, primary energy does not include energy derived from on-site renewable energy technologies. In addition, as renewable energy technologies are generally characterised by zero, or greatly reduced CO2 emissions, the calculated EPC and CPC are reduced by the extent that they replace traditional fossil fuels.
As the performance of the reference dwelling (see Appendix C) is not affected by the incorporation of these technologies in a dwelling being assessed, this has the effect of making it easier to achieve compliance with this Part of the Building Regulations when these technologies are used.
For certain dwelling types, use of renewables may prove the most practical approach to achieving compliance. The use of centralised renewable energy sources contributing to a heat distribution system serving all dwelling units in a development or apartment block may prove to be more practicable than providing separate renewable energy for each dwelling individually.
Renewable Energy Technologies
This section gives guidance on the minimum level of renewable technologies to be provided to show compliance with Regulation 8(b) of the European Union (Energy Performance of Buildings) Regulations 2019.
Renewable Energy Ratio (RER) is the ratio of the primary energy from renewable energy technologies to total primary energy as defined and calculated in DEAP.
For the purposes of this Section, “renewable energy technologies” means technology, products or equipment that supply energy derived from renewable energy sources, e.g. solar thermal systems, solar photovoltaic systems, biomass systems, systems using biofuels, heat pumps, aerogenerators and other small scale renewable systems.
Where the MPEPC of 0.3 and MPCPC of 0.35 are achieved, a RER of 0.20 represents a very significant level of energy provision from renewable energy technologies. A RER of 0.2 represents 20 % of the primary energy from renewable energy technologies to total primary energy as defined and calculated in DEAP.
Where a building contains more than one dwelling, reasonable provision would be to show that:
every individual dwelling should meet the minimum provision from renewable energy technologies specified in paragraph 1.2.3 above; or
the average contribution of renewable technologies to all dwellings in the building should meet that minimum level of provision per dwelling.
Where there are both common areas and individual dwellings in a building, reasonable provision would be to show that the average contribution of renewable technologies to all areas meets the minimum level of renewable provision to the individual dwellings and common areas combined. In this case, a proportion of the renewables should be provided to each area and individual dwelling in the building.
In the case of heat pumps, DEAP sets the procedure to calculate the renewable energy provision for use in the Renewable Energy Ratio. In the case of systems based on biofuels or biomass, appliances must be designed to run on these fuels only, i.e. incapable of providing thermal energy from fossil fuels, to be accepted as renewable technology for the purposes of this Regulation.
For example, a boiler which could operate on either oil or a biofuel mixture would not be considered to be a renewable technology. Similarly a boiler capable of utilizing coal or peat, in addition to a biomass fuel would not be considered a renewable technology.
The use of centralised renewable energy sources contributing to a heat distribution system serving all dwelling units in a district, an area, a development or part of a development, e.g. an apartment block, may prove to be more practicable than providing separate renewable energy for each dwelling individually and may be counted towards the Renewable Energy Ratio.
As an alternative to providing the RER (Renewable Energy Ratio) as outlined in subsection 1.2.2, the use of a combined heat and power (CHP) system that contributes to the space and water heating energy use would be acceptable.
The primary energy savings due to the use of CHP should be equivalent to the RER of 0.20 contributing to the thermal energy use within the building. The calculation methodology for the primary energy saving contribution is provided in the DEAP calculation.
The design of the CHP system should take account of the output rating of the appliance and the design thermal profile for the development for which it is designed.
It should be suitable for the building application (simultaneous electrical and thermal profile requirements) and not oversized.
Further guidance with regards to the design of CHP systems is available in CIBSE Manual AM 12 Combined Heat and Power in Buildings for both high-density developments and individual dwellings.
Section 4.4 of CIBSE Manual AM 12 details an operating model for CHP sizing and recommends the use of an hour-by-hour model over a whole year with heat and electricity demand profiles representing an average year.
Part D of the Building Regulations requires that all works be carried out with proper materials and in a workmanlike manner. “Materials” includes products, components and items of equipment, and guidance is provided on how products, components and items of equipment can be shown to be “proper materials”. Renewable technologies should satisfy the requirements of Part D in the same way as other construction products and materials. A range of standards applicable to renewable energy technologies are given in the “Other standards and publications” Section in this document.
For specific renewable technologies, the SEAI maintain databases of acceptable products together with information on relevant performance characteristics. Products listed in these databases may be assumed to be “proper materials” for the purposes of this Part of the Building Regulations. Databases exist for:
solar thermal systems;
wood pellet stoves;
wood pellet/chip boilers;
heat pumps.
To ensure that works are carried out in a “workmanlike manner”, the design and installation of renewable energy systems to comply with this guidance should be carried out by a person qualified to carry out such work.
A suitably qualified installer should have achieved Quality and Qualifications Ireland (QQI) or equivalent certification from an accredited training course in each of the technology areas they wish to work in. Qualified installers may include SEAI registered installers, Solas trained plumbers or Solas trained electricians, who have completed an appropriate renewable technology module, or similar.
Detailed guidance on the specification of renewable technologies for dwellings is contained in the Technical Guidance Document supporting document “Heating and Domestic Hot Water Systems for Dwellings – Achieving compliance with Part L and Energy Performance of Buildings Regulations 2019” (to be published) and the National Standards Authority of Ireland’s NSAI S.R.50-2: 2012, Code of practice for building services - Part 2: Solar panels.
Building Fabric
General
This section gives guidance on acceptable levels of provision to ensure that heat loss through the fabric of a dwelling is limited insofar as reasonably practicable. Guidance is given on three main issues:
insulation levels to be achieved by the plane fabric elements (sub-section 1.3.2);
thermal bridging (sub-section 1.3.3); and
limitation of air permeability (sub-section 1.3.4).
Unheated areas which are wholly or largely within the building structure, do not have permanent ventilation openings and are not otherwise subject to excessive air infiltration or ventilation, e.g. common areas such as stairwells, corridors in buildings containing flats, may be considered as within the insulated fabric.
In that case, if the external fabric of these areas is insulated to the same level as that achieved by equivalent adjacent external elements, no particular requirement for insulation between a heated dwelling and unheated areas would arise, subject to achieving the EPC and CPC requirements.
It should be noted that heat losses to such unheated areas are taken into account by the DEAP methodology in the calculation of the dwelling EPC and CPC (see Section 1.1).
Fabric insulation
The derivation of U-values, including those applicable where heat loss is to an unheated space, is dealt with in paragraphs 0.3.4 to 0.3.8 and Appendix A.
In order to limit heat loss through the building fabric reasonable provision should be made to limit transmission heat loss by plane elements of the building fabric.
Acceptable levels of thermal insulation for each of the plane elements of the building to achieve this are specified in terms of average area weighted U-value (Um) in Table 1 (Column 2) for each fabric element type. 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 of Table 1. Where this relaxation is availed of, the average area-weighted values given in Column 2 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 the source of space heating is underfloor heating, the maximum floor U-value should be 0.15 W/m2K.
Reasonable provision would also be achieved if the total heat loss through all the opaque elements did not exceed that which would be the case if each of the area weighted average U-value (Um) set out in Table 1 were achieved individually.
Where this approach is chosen, the values for individual elements or sections of elements given in Table 1 (Column 3) also apply. For ground floors or exposed floors incorporating underfloor heating, the guidancein paragraph 1.3.2.2 applies.
Table HL1 - Maximum elemental U-value (W/m²K) - Extract from TGD L
The area of openings should not be reduced below that required for the provision of adequate daylight. BS 8206-2:2008 Code of Practice for daylighting and CIBSE Lighting Guide LG 10 gives advice on adequate daylight provision.
Diagram 1 summarises the minimum fabric insulation standards applicable.
Diagram HL1 - Average area weighted elemental U-values - Extract from TGD L
** Thermal bridging**
To avoid excessive heat losses and local condensation problems,reasonable care should be taken to ensure continuity of insulation and to limit local thermal bridging at key junctions, e.g. around windows, doors, other wall openings and at junctions between elements. Any thermal bridge should not pose a risk of surface or interstitial condensation. Appendix D.2 provides further information on assessing surface condensation risk and Appendix B.3 provides information on assessing interstitial condensation risk.
Heat loss associated with thermalbridges is taken into account in calculating energy use and CO2 emissions using the DEAP methodology. See Appendix D for further information in relation to thermal bridging and its effect on dwelling heat loss and how this is taken account of in DEAP calculations.
The following represents alternative approaches to making reasonable provision with regard to limitation of thermal bridging:
(i) adopt Acceptable Construction Details for typical constructions as shown in sections 1 to 6 in the document “Limiting Thermal Bridging and Air Infiltration – Acceptable Construction Details” for all key junctions;
(ii) adopt Acceptable Construction Details sections 1 to 6 combined with details from Appendix 2 of the document “Limiting Thermal Bridging and Air Infiltration – Acceptable Construction Details” or other certified details (as defined in (iii) below) for all key junctions;
(iii) use certified details which have been assessed in accordance, and comply with Appendix D, e.g. certified by a third party certification body such as Agrément or equivalent or certified by a member of an approved thermal modelers scheme or equivalent for all key junctions;
(iv) use alternative details which limit the risk of mould growth and surface condensation to an acceptable level as set out in paragraph D.2 of Appendix D for all junctions.
Irrespective of which approach is used, appropriate provision for on-site inspection and related quality control procedures should be made (see sub-sections 1.5.2 and 1.5.3).
The DEAP calculation of primary energy use and CO2 emissions (see Section 1.1) takes account of thermal bridging effects. In general this is done by including an allowance for additional heat loss due to thermal bridging, expressed as a multiplier applied to the total exposed surface area or by the calculation of the transmission heat loss coefficient HTB.
Where provision for thermal bridging is made in accordance with option (i) of paragraph 1.3.3.2, this multiplier (y) may be taken as 0.08 or the transmission heat loss coefficient (HTB) can be calculated for each of the key junctions for the specific dwelling using the psi values given in Tables D1 to D6 in Appendix D.
Where provision for thermal bridging is made in accordance with option (ii) of paragraph 1.3.3.2, the transmission heat loss coefficient (HTB) should be calculated using the psi values associated with the specific details adopted (i.e. Tables D1 to D6 and Appendix 2 of “Limiting Thermal Bridging and Air Infiltration – Acceptable Construction Details” or other certified Psi values).
Where provision for thermal bridging is made in accordance with option (iii) of paragraph 1.3.3.2, the transmission heat loss coefficient (HTB) should be calculated using the psi values associated with the certified specific details adopted.
Where provision for thermal bridging is made in accordance with option (iv) of paragraph 1.3.3.2, this multiplier (y) should be taken as 0.15.
As an alternative to all of the above, the value 0.15 may be used for the multiplier (y) providing the details used limit the risk of mould growth and surface condensation to an acceptable level as set out in paragraph D.2 of Appendix D for all junctions.
The calculation of transmission heat loss (HTB) coefficient is explained in paragraph D.3 of Appendix D, and in Appendix K of the DEAP manual. A detailed example of a (y) value calculation using option (i) of 0.05 is provided in Appendix D, Table D7.
The DEAP Methodology provides a software tool to calculate the (y) value with ACDs and/or custom junctions.
Building envelope air permeability
To avoid excessive heat losses, reasonable care should be taken to limit the air permeability of the envelope of each dwelling. In this context, envelope is the total area of all floors, walls (including windows and doors) and ceilings bordering the dwelling, including elements adjoining other heated or unheated spaces.
High levels of infiltration can contribute to uncontrolled ventilation. Infiltration is unlikely to provide adequate ventilation as required in the correct location.
It is important, as air permeability is reduced, that adequate purpose designed ventilation is provided.
Technical Guidance Document F provides guidance for adequate ventilation for buildings.
The following represents a reasonable approach to the design and construction of dwellings to ensure acceptable levels of air permeability:
a) identify the primary air barrier elements, (e.g. sheathing, plaster, vapour control layer, breather membrane) at early design stage;
b) develop appropriate details and performance specification to ensure continuity of the air barrier. Communicate these to all those involved in the construction process. Responsibility for construction of details should be established;
c) provide on-site inspection regime and related quality control procedures so as to ensure that the design intention is achieved in practice.
Achievement of reasonable levels of air permeability can be facilitated by adopting the standard details referred to in paragraph 1.3.3.2 above, together with an appropriate performance specification and the on-site inspection regime and related quality control procedures, referred to in that paragraph.
Alternative approaches to element design, details and quality control procedures may also be acceptable, provided it can be shown that these approaches provide an equivalent level of performance, as if the standard details, performance specification and quality control procedures referred to above were adopted.
Air pressure testing should be carried out on all dwellings on all development sites. See sub-section 1.5.4 for details of the test procedure, use of test results in DEAP calculations and appropriate measures to be undertaken where the limit set is not achieved. When tested in accordance with the procedure referred to in sub-section 1.5.4, a performance level of 5m^3^/(h.m^2^) represents a reasonable upper limit for air permeability.
Limiting Heat Gains
Guidance is provided in DEAP for carrying out overheating assessment.
Reasonable provision to limit heat gains can be demonstrated by showing through the DEAP calculation that the dwelling does not have a risk of high internal temperatures. (revised DEAP methodology to be published).
Where an overheating risk is indicated in DEAP, further guidance is provided in CIBSE TM 59 to ensure overheating is avoided for normally occupied naturally ventilated spaces.
CIBSE TM 37 provides the following recommendations and further guidance to reduce or avoid solar overheating:
a) Layout: planning the layout and orientation of buildings and rooms to maximise the benefits of sunlight and minimise the disadvantages.
b) Solar shading: this may include external, internal or mid-pane shading devices, or solar control glazing.
c) Thermal mass: an exposed heavyweight structure, with a long response time, will tend to absorb heat, resulting in lower peak temperatures on hot days. Night-time venting and acoustic requirements should also be considered.
d) Good ventilation: a reasonable level of ventilation will always be required in buildings to maintain indoor air quality. The ability to switch to a much higher air change rate can be a very effective was to control solar overheating, e.g. cross ventilation, stack ventilation or mechanical ventilation.
e) Reducing internal gains: by the use of e.g. energy efficient equipment, lamps, luminaires and controls.
Building Services
General
Regulation 8(d) requires that space and water heating systems in dwellings be energy efficient, with efficient heat sources and effective controls. More specifically, Regulation 8(e) provides that oil or gas fired boilers must achieve a minimum seasonal efficiency of 90 %.
This Section gives guidance for dwellings where the main space and water heating is based on pumped low temperature hot water systems, utilising radiators for space heating and incorporating a hot water cylinder for the storage of domestic hot water. Guidance is given on three main issues:
a) heat generator efficiency (sub-section 1.4.2);
b) space heating and hot water supply system controls (sub-section 1.4.3); and
c) insulation of hot water storage vessels, pipes and ducts (sub-section 1.4.4).
This Section also contains guidance in relation to the energy efficiency aspects of: (a) biomass independent boilers (paragraph 1.4.2.3); and (b) mechanical ventilation systems, (subsection 1.4.5) where provided.
Heat generator efficiency
The appliance or appliances provided to service space heating and hot water systems should be as efficient in use as is reasonably practicable. For fully pumped hot water-based central heating systems utilising oil or gas, the boiler seasonal efficiency should be not lessthan 90 % as specified in the DEAP manual and the associated Homeheating Appliance Register of Performance (HARP) database maintained by the SEAI http://www.seai.ie/harp.
For fully pumped hot water-based central heating systems heat pumps, the seasonal space heating energy efficiency and water heating energy efficiency should not be less than the minimum requirements inaccordance with Ecodesign regulations.
For fully pumped hot water-based central heating systems utilising a biomass independent boiler, the boiler seasonal efficiency should not be less than 77 % as specified in the DEAP manual and the associated Home-heating Appliance Register of performance (HARP) database maintained by the SEAI http://www.seai.ie/harp.
Guidance for minimum efficiencies for other heat generating appliances can be found in Heating and Domestic Hot Water Systems for Dwellings – Achieving compliance with Part L and Energy Performance of Buildings Regulations 2019 (to be published).
Space heating and hot water supply system controls
Space and water heating systems should be effectively controlled so as to ensure the efficient use of energy by limiting the provision of heat energy use to that required to satisfy user requirements, insofar as is reasonably practicable. The aim should be to provide the following minimum level of control:
automatic control of space heating on the basis of room temperature;
automatic control of heat input to stored hot water on the basis of stored water temperature;
separate and independent automatic time control of space heating and hot water;
shut down of boiler or other heat source when there is no demand for either space or water heating from that source.
The guidance in paragraphs 1.4.3.2 to 1.4.3.5 below is specifically applicable to fully pumped hot water-based central heating systems using gas, oil or biomass boilers.
The minimum requirements for controls for heating systems using heat pumps are set out in Tables 2 and 3.
The minimum requirements for controls for all other heating systems are set out in Heating and Domestic Hot Water Systems for Dwellings – Achieving compliance with Part L and Energy Performance of Buildings Regulations 2019 (to be published).
Table HL2 - Minimum controls for DHW and space heating for ground-to-water, water-to-water and air-to-water heat pump - Extract from TGD L
Table HL3 - Minimum controls for DHW and space-heating for ground-to-air, water-to-air and air-to-air heat pump systems - Extract from TGD L
Provision should be made to control heat input on the basis of temperature within the heated space, e.g. by the use of room thermostats, thermostatic radiator valves, or other equivalent form of sensing device. For larger dwellings, independent temperature control should generally be provided for separate zones that normally operate at different temperatures, e.g. living and sleeping zones.
Thermostats should be located in a position representative of the temperature in the area being controlled and which is not unduly influenced by draughts, direct sunlight or other factors which would directly affect performance. Depending on the design and layout of the dwelling, control on the basis of a single zone will generally be satisfactory for smaller dwellings.
For larger dwellings, e.g. where floor area exceeds 100sqm, independent temperature control on the basis of two independent zones will generally be appropriate. In certain cases, additional zone control may be desirable, e.g. zones which experience significant solar or other energy inputs may be controlled separately from zones not experiencing such inputs.
Hot water storage vessels should be fitted with thermostatic control that shuts off the supply of heat when the desired storage temperature is reached.
Separate and independent time control for space heating and for heating of stored water should be provided. Independent time control of space heating zones is appropriate where independent temperature control applies.
The operation of controls should be such that the oil or gas boiler is switched off when no heat is required for either space or water heating, i.e. boiler interlock. Systems controlled by thermostatic radiator valves should be fitted with flow control or other equivalent device to ensure boiler switch off.
Insulation of hot water storage vessels, pipes and ducts
All hot water storage vessels, pipes and ducts associated with the provision of heating and hot water in a dwelling should be insulated to prevent heat loss. Hot water pipes and ducts within the normally heated area of the dwelling that contribute to the heat requirement of the dwelling do not require insulation (except those referred to in paragraph 1.4.4.4). Pipes and ducts which are incorporated into wall, floor or roof construction should be insulated.
Adequate insulation of hot water storage vessels can be achieved by the use of a storage vessel with factory applied insulation of such characteristics that, when tested on a 120 litre cylinder complying with I.S. 161: 1975 using the method specified in Annex B of BS 1566-1:2002+A1:2011, standing heat losses are restricted to 0.8 W/litre.
Use of a storage vessel with 50mm, factory applied coating of PU-foam having zero ozone depletion potential and a minimum density of 30kg/m3 satisfies this criterion when installed within the normally heated areaof the dwelling. Alternative insulation measures giving equivalent performance may also be used.
Unless the heat loss from a pipe or duct carrying hot water contributes to the useful heat requirement of a room or space, the pipe or duct should be insulated. The following levels of insulation should suffice:
a) pipe or duct insulation meeting the recommendations of BS 5422:2009 Methods of specifying thermal insulating materials for pipes, ductwork and equipment (in the temperature range – 40 deg. C to + 700 deg. C); or
b) insulation with material of such thickness that gives an equivalent reduction in heat loss as that achieved using material having a thermal conductivity at 40 deg. C of 0.035 W/mK and a thickness equal to the outside diameter of the pipe, for pipes up to 40 mm diameter, and a thickness of 40 mm for larger pipes.
The primary flow and return from the heat generator to the heat exchanger should be insulated. The hot pipes connected to hot water storage vessels, including the vent pipe, should be insulated for at least one metre from their point of connection. All insulation of pipes should be to the standard outlined in paragraph 1.4.4.3 above.
It should be noted that water pipes and storage vessels in unheated areas will generally need to be insulated for the purpose of protection against freezing. Guidance on suitable protection measures is given in Technical Guidance Document G and Report BR 262 Thermal insulation: avoiding risks, published by BRE.
Mechanical ventilation systems
Guidance on good practice with regard to energy efficiency of dwelling ventilation systems is contained in GPG 268 Energy efficient ventilation in dwellings – a guide for specifiers, available from the SEAI.
Where a mechanical ventilation system designed for continuous operation(with or without heat recovery) is installed for the provision of ventilation to a dwelling or significant part thereof, the system should meet the performance levels specified in GPG 268 and also have specific fan power and heat recovery efficiency backstop values where appropriate not worse than those given in Table 4. Performance data for mechanical ventilation systems from system manufacturers for use in DEAP should be in compliance with the DEAP methodology.
Table HL4 - Minimum performance levels for mechanical ventilation systems - Extract from TGD L
The effectiveness of mechanical ventilation systems improve as air permeability values decrease. Air permeability values of less than 3 m^3^ /(hr.m^2^ ) at 50 Pa are recommended in dwellings with mechanical ventilation, especially ventilation systems with heat recovery.
Table 4 does not apply to fans installed for intermittent use in individual rooms.
Construction Quality and Commissioning of Services
General
The requirements of Part L and of the European Union (Energy Performance of Buildings) Regulations 2019 apply to the completed building. Reasonable measures should be taken during construction and appropriate checks and assessments carried out prior to completion to ensure that compliance with Part L and the European Union (Energy Performance of Buildings) Regulations is achieved. Sub-sections 1.5.2 to 1.5.4 give guidance on appropriate measures to satisfy this requirement.
Insulation continuity and air permeability
The elements that comprise the external fabric of the building should be designed and constructed to ensure that the calculated performance of the building and of its components is achieved in practice. Changes made during design and construction should be assessed for their impact on insulation performance and on air permeability. Those not directly involved in the installation of insulation should be fully aware of the importance of not reducing the effectiveness of the installed insulation through removal or damage. On-site quality control should include checks on the adequacy of insulation installation and of any barriers designed to limit air permeability, including an inspection of finished work to ensure that all work is properly constructed before covering over.
Thermal bridging
There should be no reasonably avoidable thermal bridging, e.g. due to gaps between insulation layers and at joints, junctions and edges around openings. Where unavoidable thermal bridging is provided for in the design, care should be taken to ensure that the chosen design detail is accurately constructed on site.
Air permeability pressure tests
Air permeability can be measured by means of pressure testing of a building prior to completion. The procedure for testing is specified in I.S. EN ISO 9972:2015 Thermal performance of buildings - determination of air permeability of buildings - fan pressurization method. Additional guidance on testing procedure is given in NSAI Agrément Approval Scheme for certified air tightness testers scheme master document to I.S. EN ISO 9972:2015 Thermal performance of buildings - determination of air permeability of buildings - fan pressurization method.
The preferred test method is that controllable ventilator grills should be temporarily sealed rather than just closed. Two sets of measurements should be made for pressurisation and depressurisation.
Permeability is calculated by dividing the air leakage rate in m3 /hr by the envelope area in m^2^ . The performance is assessed at 50 Pa pressure difference. It has been empirically determined that for
dwellings generally, the permeability at 50 Pa pressure difference is approximately 20 times the air change rate at normal conditions. Guidance on appropriate extent of testing is given in paragraph 1.5.4.3.
Air pressure testing should be carried out on all dwellings on all development sites including single dwelling developments, as outlined in paragraphs 1.5.4.3 to 1.5.4.5 to show attainment of backstop value of 5 m3 /hr/m2 . The tests should be carried out by a person certified by an independent third party to carry out this work, e.g. Irish National Accreditation Board (INAB), National Standards Authority of Ireland (NSAI) certified or equivalent. The test report should contain at least the information specified in Section 7 of I.S. EN 9972:2015.
If the measured air change rates are not worse than the criterion set out in paragraph 1.3.4.4, the test results should be taken as satisfactory evidence that the requirements of Regulation 8(c), insofar as it relates to air tightness, has been demonstrated for this dwelling type.
If satisfactory performance is not achieved in a particular test, then remedial measures should be carried out on the test dwelling and a new test carried out. This should be repeated until the dwelling achieves the criterion set out in paragraph 1.3.4.4.
Where the air permeability assumed for the DEAP calculations is better than the value derived from pressure test results, a check calculation should be carried out to show that the calculated EPC and CPC using the
measured air permeability (after any remedial works to satisfy paragraph 1.3.4.4, if such are necessary) are not worse than the MPEPC and MPCPC respectively. If necessary, additional remedial works or other measures should be carried out to ensure that this criterion is also met. Where further remedial works to reduce air permeability are undertaken, a further test would be necessary to verify the revised air permeability figure to be used in revised DEAP calculations.
Air pressurisation test reports should be retained by the developer of the dwelling as proof of performance, and copies included in the user information referred to in Section 1.6.
Commissioning of space and water heating systems
The heating and hot water system(s) should be commissioned so that at completion, the system(s) and their controls are left in the intended working order and can operate efficiently for the purposes of the conservation of fuel and energy. The procedure for carrying out commissioning of these systems is set out in Heating and Domestic Hot Water Systems for Dwellings – Achieving compliance with Part L and Energy Performance of Buildings Regulations 2019 (to be published).
User Information
The owner of the building should be provided with sufficient information about the building, the fixed building services and their maintenance requirements so that the building can be operated in such a manner as to use no more fuel and energy than is reasonable in the circumstances.
A way of complying would be to provide a suitable set of operating and maintenance instructions aimed at achieving economy in the use of fuel and energy in a way that householders can understand.
The instructions should be directly related to the particular system(s) installed in the dwelling. Without prejudice to the need to comply with health and safety requirements, the instructions should explain to the occupier of the dwelling how to operate the system(s) efficiently. This should include:
a) the making of adjustments to the timing and temperature control settings;
b) what routine maintenance is needed to enable operating efficiency to be maintained at a reasonable level through the service life(lives) of the system(s) and
c) the operation and maintenance of renewable energy systems.
