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Part L Energy Conservation

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Limitation of Primary Energy Use and Carbon Dioxide Emissions

1.1.1 This Section provides guidance on how to show compliance with the requirements in relation to primary energy consumption and CO~2~ emissions specified in Regulation L3(a). 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 CO~2~ emissions associated with a standardised use of a dwelling. The energy consumption is expressed in terms of kilowatt hours per square metre floor area per year (kWh/m~2~/yr) and the CO~2~ emissions expressed in terms of kilograms of CO~2~ per square metre floor area per year (kg CO~2~/m~2~/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 CO~2~ emissions for the provision of space heating, 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.

1.1.2 The performance criteria are based on the relative values of the calculated primary energy consumption and CO~2~ 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 CO~2~ 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 0.4;

  • the calculated CO~2~ 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 CO~2~ 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 0.46.

The DEAP software will calculate the EPC and CPC of the dwelling being assessed and clearly indicate whether compliance with the requirements of Regulation L3(a) has been achieved.

1.1.3 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 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.

1.1.4 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.

1.1.5 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 CO~2~ emissions. As defined, primary energy does not include energy derived from on-site renewable energy technologies. In addition, as renewable energy technologies generally are characterised by zero, or greatly reduced, CO~2~ 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

1.2.1 This section gives guidance on the minimum level of renewable technologies to be provided to show compliance with Regulation L3(b). The following represents a reasonable minimum level of energy provision from renewable energy technologies in order to satisfy Regulation L3(b): - - 10 kWh/m2 /annum contributing to energy use for domestic hot water heating, space heating or cooling; or - 4 kWh/m2 /annum of electrical energy; or - a combination of these which would have equivalent effect. 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.

1.2.2 Where a building or development 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 1.2.1 above; or - the average contribution of renewable technologies to all dwellings in the building or development should meet that minimum level of provision per dwelling. Where the latter approach is used, common areas in the building are not included in this calculation.

1.2.3 In the case of electrically powered heat pumps, only energy in excess of 2.5 times the electrical energy directly consumed by the heat pump can be counted towards a biomass fuel would not be considered a renewable technology.

1.2.4 The use of centralised renewable energy sources contributing to a heat distribution system serving all dwelling units in 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.

1.2.5 As an alternative to providing 10 kWh/m2 /annum thermal energy (or 4 kWh/m2 /annum electrical energy) from renewable technology sources, the use of a small-scale combined heat and power (CHP) system which contributes to the space and water heating energy use would be acceptable. This approach may be appropriate in some high density
developments, e.g. apartment and mixed-use developments.

The energy savings due to the use of CHP should be equivalent to 10 kWh/m2 /annum contributing to energy use for domestic hot water heating, space heating or cooling. This energy saving contribution can be calculated using: -

Where: -

Rth is the energy saving contribution from the CHP system.

CHP H is the useful heat output from the CHP system.

CHP Hη is the heat efficiency of the CHP production defined as annual useful heat output divided by the gross calorific fuel input used to produce the sum of useful heat output and electricity from CHP.

CHP Eη is the electrical efficiency of the CHP production defined as annual electricity from cogeneration divided by the fuel input used to produce the sum of useful heat output and electricity from CHP.

The design of the CHP system should take account of the output rating of the appliance and the design heat demand for the development for which it is designed. Further guidance with regards to the design of CHP systems is available in “Heating and Domestic Hot Water Systems for Dwellings – Achieving compliance with Part L 2011” (to be published).

1.2.6 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.

1.2.7 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 must have achieved FETAC 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 and FÁS trained plumbers who have completed the renewable technology module, or similar. 1.2.8 Detailed guidance on the specification of renewable technologies for dwellings is contained in the Technical Guidance Document L supporting document “Heating and Domestic Hot Water Systems for Dwellings – Achieving compliance with Part L” and the National Standards Authority of Ireland’s SR 50-2: 2011 Code of practice for building services - Part 2: Solar panels (to be published).

Building Fabric

General

1.3.1.1 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).

1.3.1.2 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-filtration 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. 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

1.3.2.1 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.

1.3.2.2 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, a floor U-value of 0.15 W/m2K should generally be satisfactory. Further guidance in relation to insulation of floors where underfloor heating is proposed is contained in the document “Heating and Domestic Hot Water Systems for Dwellings – Achieving compliance with Part L 2011” (to be published).

Table 1: Maximum elemental U-value (W/m^2^K)^1,2^

Table 2: Permitted variation in combined areas (A~ope~) and average U-Values (U~ope~) of external doors, windows and rooflights.

1.3.2.3 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 guidance in paragraph 1.3.2.2 applies.

1.3.2.4 The maximum area-weighted average U-value for doors, windows and rooflights of 1.6 W/m2K given in Table 1 applies when the combined area of external door, window and rooflight openings equals 25% of floor area. However, both the permitted combined area of external door, window and rooflight openings and the maximum area-weighted average U-value of these elements may be varied as set out in Table 2. The area of openings should not be reduced below that required for the provision of adequate daylight. BS 8206: Part 2: 2008 Code of Practice for daylight and CIBSE Lighting Guide LG 10 gives advice on adequate daylight provision.

1.3.2.5 Diagram 1 summarises the minimum fabric insulation standards applicable.

Thermal Bridging

1.3.3.1 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, e.g. around windows, doors and other wall openings, at junctions between elements and other locations. Any thermal bridge should not pose a risk of surface or interstitial condensation. Heat loss associated with thermal bridges 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.

1.3.3.2 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 (to be developed) 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).

1.3.3.3 The DEAP calculation of primary energy use and CO~2~ 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 H~TB~.

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 (H~TB~) 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 (H~TB~) 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 (H~TB~) 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 Appendix D and Appendix K of the DEAP manual.

Building envelope air permeablity

1.3.4.1 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 purpose provided ventilation is maintained.

Diagram 1: Average Area Weighted Elemental U-Values

1.3.4.2 The following represents a reasonable approach to the design and construction of dwellings to ensure acceptable levels of air permeability: -

  1. identify the primary air barrier elements, (e.g. sheathing, plaster, vapour control layer, breather membrane) at early design stage;

  2. 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;

  3. provide on-site inspection regime and related quality control procedures so as to ensure that the design intention is achieved in practice.

1.3.4.3 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.

1.3.4.4 Air pressure testing should be carried out on a proportion of dwellings on all development sites. See sub-section 1.5.4 for details of the test procedure, extent of testing, 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 7 m^3^ /(h.m^2^ ) represents a reasonable upper limit for air permeability. Where lower levels of air permeability are achieved it is important that purpose provided ventilation is maintained. For this reason Technical Guidance Document F also provides guidance for buildings with lower air permeability.

Building Services

General

1.4.1.1 Regulation L3(d) requires that space and water heating systems in dwellings be energy efficient, with efficient heat sources and effective controls. More specifically, Regulation L3(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, and the fuel used is natural gas, LPG or oil. Guidance is given on three main issues: -

  1. heating appliance efficiency (sub-section 1.4.2);

  2. space heating and hot water supply system controls (sub-section 1.4.3); and

  3. insulation of hot water storage vessels, pipes and ducts (sub-section 1.4.4).

Detailed guidance for dwellings using a wide range of space and water heating systems is contained in a supporting document “Heating and Domestic Hot Water Systems for Dwellings – Achieving compliance with Part L 2011” (to be published).

1.4.1.2 This Section also contains guidance in relation to the energy efficiency aspects of: -

  1. biomass independent boilers (paragraph 1.4.2.2), and

  2. mechanical ventilation systems, (subsection 1.4.5), where provided.

Heating appliance efficiency

1.4.2.1 The appliance or appliances provided to service space heating and hot water systems should be as efficient in use as reasonably practicable. For fully pumped hot water-based central heating systems utilising oil or gas, the boiler seasonal efficiency should be not less than 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).

1.4.2.2 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).

Space heating and hot water supply system controls

1.4.3.1 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 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;

Insulation of hot water storage vessels, pipes and ducts

1.4.4.1 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.

1.4.4.2 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 BS 1566, Part 1: 2002, Appendix B, standing heat losses are restricted to 0.8 W/litre. Use of a storage vessel with 50 mm, factory applied coating of PU-foam having zero ozone depletion potential and a minimum density of 30 kg/m3 satisfies this criterion when installed within the normally heated area of the dwelling. Alternative insulation measures giving equivalent performance may also be used.

1.4.4.3 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: -

  1. 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^o^C to + 700^o^C); or

  2. insulation with material of such thickness as gives an equivalent reduction in heat 23 loss as that achieved using material having a thermal conductivity at 40^o^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.

1.4.4.4 The hot pipes connected to hot water storage vessels, including the vent pipe and the primary flow and return to the heat exchanger, where fitted, should be insulated, to the standard outlined in paragraph1.4.4.3 above, for at least one metre from their point of connection.

1.4.4.5 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

1.4.5.1 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.

1.4.5.2 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 3. Performance data for mechanical ventilation systems from system manufacturers for use in DEAP can be obtained from the SAP Appendix Q database at http://www.sap-appendixq.org.uk. The effectiveness of mechanical ventilation systems improve as air permeability values decrease. Air permeability values of less than 5m^3^/(hr.m^2^ ) at 50pa are recommended in dwellings with mechanical ventilation, especially ventilation systems with heat recovery. Table 3 does not apply to fans installed for intermittent use in individual rooms.

Table 3: Minimum performance levels for mechanical ventilation systems

Construction Quality and Commissioning of Services

General

1.5.1.1 The requirements of Part L 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 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

1.5.2.1 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

1.5.3.1 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.

Insulation of hot water storage vessels, pipes and ducts

1.5.4.1 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 13829: 2000 “Thermal performance of buildings: determination of air permeability of buildings: fan pressurization method”. Additional guidance on testing procedure is given in Sections 2 to 4 of the BSRIA Guide “Airtightness testing for new dwellings” and CIBSE Technical Manual TM 23 “Testing Buildings for Air leakage” and the ATTMA publication “Measuring air permeability of Building Envelopes”. The preferred test method is that controllable ventilator grills should be temporarily sealed rather than just closed. Permeability is calculated by dividing the air leakage rate in m^3^/hr by the envelope area in m^2^ . The performance is assessed at 50 Pascals pressure difference. It has been empirically determined that for dwellings generally the permeability at 50 Pascals 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.

1.5.4.2 Subject to the guidance in paragraph 1.5.4.7, air pressure testing should be carried out on a proportion of dwellings on all development sites including single dwelling developments, as outlined in paragraphs 1.5.4.3 to 1.5.4.6 to show attainment of backstop value of
7m^3^/hr/m^2^ . The tests should be carried out by a person certified by an independent third party to carry out this work, e.g. National Standards Authority of Ireland certified or equivalent. The test report should contain at least the information specified in Section 7 of I.S. EN 13829.

1.5.4.3 On each development, an air pressure test should be carried out on at least one unit of each dwelling type. One dwelling from the first four units of each dwelling type planned for completion should be tested. The basic number of tests for each dwelling type is presented in Table 4. The total number tested is related to the number of units of that type in the development and to the results achieved in any earlier tests carried out. Where a number of apartment blocks are constructed on the same site, each block should be treated as a separate development irrespective of the number of blocks on the site.

Table 4: Number of pressure tests per dwelling type

1.5.4.4 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 Part L3(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. Dwellings completed later than the most recent successful test on a dwelling of this type should either have similar remedial work carried out or should be subject to pressure testing.

1.5.4.5 Where remedial work and a new test 25 is required on any dwelling following the initial test, the size of sample for testing should be increased by one, for that dwelling type.

1.5.4.6 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 revised air permeability figure to be used in revised DEAP calculations.

1.5.4.7 Where an air permeability value better than the backstop value of 7m^3^/hr/m^2^ at 50 Pascals is claimed for use in DEAP, a test should be performed on each dwelling claiming that value.

1.5.4.8 For small developments comprising no more than three dwelling units, specific pressure testing of these dwellings would not be necessary if it can be demonstrated with air pressure test reports that, during the preceding 12 month period, a dwelling of the same dwelling type constructed by the same builder had been pressure tested according to the procedures given in this sub-section and had satisfied the criterion set in paragraph 1.3.4.4. However, if the assumed air change rate in the calculation of the EPC and CPC using the DEAP methodology is less than the criterion set in paragraph 1.3.4.4, a pressure test to verify this assumed value should be carried out. The guidance given in this sub-section would apply in this situation.

1.5.4.9 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.

1.5.5 Commissioning space and water heating systems

1.5.5.1 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 2011” (to be published).

User Information

1.6.1 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: -

  1. the making of adjustments to the timing and temperature control settings; and

  2. 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).

The information to satisfy this requirement may be provided in the context of the Advisory Report to the mandatory Building Energy Rating certificate, augmented as appropriate.