Application of the Regulations
The aim of Part L of the Second Schedule to the Building Regulations is to limit the use of fossil fuel energy and related carbon dioxide (CO~2~) emissions arising from the operation of buildings, while ensuring that occupants can achieve adequate levels of lighting and thermal comfort. Buildings should be designed and constructed to achieve this aim as far as is practicable.
The guidance in this document applies to works to dwellings only. Guidance for buildings other than dwellings can be found in a separate Technical Guidance Document L - Buildings other than dwellings.
New Dwellings
Whole dwelling performance
For new dwellings, the key issues to be addressed in order to ensure compliance are:
Whole dwelling performance
(a) Primary energy consumption and related CO~2~ emissions: providing that the calculated primary energy consumption associated with the operation of the dwelling and the related CO~2~ emissions when calculated using the Dwelling Energy Assessment Procedure (DEAP) published by the Sustainable Energy Authority of Ireland, as described in Section 1.1, do not exceed a target value specified in this document;
Individual minimum performance levels
The performance levels specified for items (b) to (i) below 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 with Regulation L3(a).
Meeting the performance levels specified for items (b) to (i) will not necessarily mean that the level specified for primary energy consumption and related CO2 emissions [item (a)] will be met. One or more of the
performance levels specified, for items (b) to (i), will need to be exceeded to achieve this.
Use of renewable energy sources: providing that the contribution of low or zero carbon energy sources to the calculated primary energy requirement meets the target for such contribution as set down in Section 1.2;
Fabric insulation: providing for fabric insulation, including the limitation of thermal bridging, which satisfies the guidance in this regard as set out in Section 1.3 (sub-sections 1.3.2 to 1.3.3);
Air tightness: limiting air infiltration as set out in sub-section 1.3.4;
Boiler efficiency: providing an efficient boiler or other heat source as set out in sub-section 1.4.2;
Building Services Controls: controlling, as appropriate, the demand for, and output of, space heating and hot water services provided, as set out in subsection 1.4.3;
Insulation of pipes, ducts and vessels: limiting the heat loss from pipes, ducts and vessels used for the transport or storage of heated water or air, as set out in sub-section 1.4.4;
Mechanical Ventilation Systems: providing that, where a mechanical ventilation system is installed, the system meets reasonable performance levels, as set out in sub-section 1.4.5;
Performance of completed dwelling: ensure design and construction process are such that the completed building satisfies compliance targets and design intent. Guidance is given in Section 1.5;
User information
- Ensure that adequate operating and maintenance instructions are available to facilitate operation in an energy efficient manner. Guidance is given in Section 1.6.
0.1.2.2 This revision of Part L builds on the previous revision in 2007 and is the next step towards the optimisation of the efficiency of energy use in new dwellings and the minimisation of related CO~2~ emissions. The overall aim is to achieve carbon neutral dwellings at the earliest date practicable.
0.1.2.3 Consideration may be given to the future upgrading of the building fabric and fixed services so as to reduce further CO~2~ emissions associated with the operation and use of these dwellings.
0.1.2.4 Where a dwelling has an attached room or space that is to be used for commercial purposes (e.g. workshop, surgery, consulting room or office), such room or space should be treated as part of the dwelling if the commercial part could revert to domestic use on a change of ownership, e.g. where there is direct access between the commercial space and the living accommodation, both are contained within the same thermal envelope and the living accommodation occupies a substantial proportion of the total area of the building. Where a new dwelling forms part of a larger building, the guidance in this document applies to the individual dwelling, and the relevant guidance in Technical Guidance Document L - Conservation of Fuel and Energy – Buildings other than dwellings applies to the non-dwelling parts of the building such as common areas (including common areas of apartment blocks), and in the case of mixed-use developments, the commercial or retail space.
0.1.2.5 The guidance given in this Technical Guidance Document is generally applicable to all works associated with the construction of new dwellings. However, unheated ancilliary areas, e.g. a buffer space for solar preheating of ventilation air which are not intended for use as part of the habitable dwelling area should generally be treated as outside the area assessed in relation to energy consumption and CO~2~ emissions (see Section 1.1). However, where such areas have the potential to become part of the habitable area, e.g. attached garages, the external fabric elements should comply with the guidance in relation to fabric insulation given in sub-sections 1.3.2 and 1.3.3.
An attached conservatory-style sunspace, or the like, forming part of a new dwelling construction should be treated as an integral part of the habitable area of the dwelling.
Existing Dwellings
0.2 Technical Risks and Precautions
0.2.1.1 The incorporation of additional thickness of thermal insulation and other energy conservation measures can result in changes in traditional construction practice. Appendix B contains general guidance on the construction and installation for common forms of construction for roofs, walls and floors.
0.2.1.2 Care should be taken in design and construction to ensure that changes do not increase the risk of certain types of problems, such as rain penetration and condensation. Some guidance on avoiding such increased risk is given in Appendix B of this document. General guidance on avoiding risks that may arise is also contained in the publication “Thermal insulation: avoiding risks; Building Research Establishment (Ref BR 262)”.
0.2.1.3 Guidance in relation to particular issues and methods of construction will be found in relevant standards.
Existing dwellings
0.1.3.1 This amendment applies to all works to existing dwellings that are covered by the requirements of the Building Regulations, including extensions, material alterations, material changes of use and window and door replacement. In carrying out this work, the aim should be to limit energy requirements for the operation of the dwelling and associated CO2 emissions as far as practicable as required by Regulation L1. Specifically, Regulation L2(d) provides that replacement oil and gas boilers should achieve a seasonal efficiency of 90% where practicable. The key issues to be addressed are: -
Fabric insulation: providing reasonable levels of fabric insulation in all new construction, including the limitation of thermal bridging including, where provided, replacement windows and doors. Guidance is given in sub-sections 2.1.2 and 2.1.3;
Air tightness: limiting air infiltration through the newly constructed elements as far as practicable. Guidance is given in sub-section 2.1.4;
Boiler efficiency: providing an efficient boiler or other heat source as set out in sub-section 2.2.2;
Building Services Controls: where new space and/or water heating services are provided, controlling, as appropriate, the demand for, and output of, these space heating and hot water services. Guidance on appropriate measures is given in sub-section 2.2.3;
Insulation of pipes, ducts and vessels: limiting the heat loss from pipes, ducts and vessels used for the transport or storage of heated water or air, as set out in sub-section 2.2.4.
Technical Risks and Precautions
0.2 Technical Risks and Precautions
0.2.1.1 The incorporation of additional thickness of thermal insulation and other energy conservation measures can result in changes in traditional construction practice. Appendix B contains general guidance on the construction and installation for common forms of construction for roofs, walls and floors.
0.2.1.2 Care should be taken in design and construction to ensure that changes do not increase the risk of certain types of problems, such as rain penetration and condensation. Some guidance on avoiding such increased risk is given in Appendix B of this document. General guidance on avoiding risks that may arise is also contained in the publication “Thermal insulation: avoiding risks; Building Research Establishment (Ref BR 262)”.
0.2.1.3 Guidance in relation to particular issues and methods of construction will be found in relevant standards.
Fire Safety
0.2.2.1 Part B of the Second Schedule to the Building Regulations prescribes fire safety requirements. In designing and constructing buildings to comply with Part L, these requirements must be met and the guidance in relation to fire safety in Technical Guidance Document B should be fully taken into account. In particular, it is important to ensure that windows, which provide secondary means of escape in accordance with Section 1.5 of Technical Guidance Document B, comply with the dimensional and other guidance for such windows set out in paragraph 1.5.6 of Technical Guidance Document B.
Ventilation
0.2.3.1 Part F of the Second Schedule to the Building Regulations prescribes ventilation requirements both to meet the needs of the occupants of the building and to prevent excessive condensation in roofs and roofspaces. A key aim of the provisions in relation to ventilation of occupied spaces is to minimise the risk of condensation, mould growth or other indoor air quality problems. In addition to meeting the requirements of Part F of the Building Regulations, the avoidance of excessive condensation requires that appropriate heating and ventilation regimes be employed in occupied dwellings. Advice for house purchasers and occupants on these issues is published separately by both HomeBond and the Sustainable Energy Authority of Ireland.
0.2.3.2 Part J of the Second Schedule to the Building Regulations prescribes requirements in relation to the supply of air for combustion appliances, including open-flued appliances which draw air from the room or space in which they are situated. Technical Guidance Document J provides guidance in this regard.
Thermal Conductivity and Thermal Transmittance
0.3.1 Thermal conductivity (λ-value) relates to a material or substance, and is a measure of the rate at which heat passes through a uniform slab of unit thickness of that material or substance, when unit temperature difference is maintained between its faces. It is expressed in units of Watts per metre per degree (W/mK).
0.3.2 For the purpose of showing compliance with this Part of the Building Regulations, design λ-values based on manufacturers declared values should be used. For thermally homogeneous materials, declared and design values should be determined accordance with I.S. EN ISO 10456: 2007. Design values for masonry materials should be determined in accordance with I.S. EN 1745: 2002. For insulation materials, values determined in accordance with the appropriate harmonised European standard should be used. Certified λ-values for foamed insulant materials should take account of the blowing agent actually used. The use of HCFC for this purpose is no longer permitted. For products or components for which no appropriate standard exists, measured values, certified by an approved body or certified laboratory (see Technical Guidance Document D), should be used.
0.3.3 Table A1 of Appendix A contain λ values for some common building materials. These are primarily based on data contained in I.S. EN ISO 10456: 2007 or in CIBSE Guide A, Section A3. These publications also include common values for insulation materials. The values provide a general indication of the thermal conductivity that may be expected for these materials. In the absence of declared values, design values or certified measured values as outlined in paragraph 0.3.2, values of thermal conductivity given in Table A1 may be used. However, values for specific products may differ from these illustrative values. Compliance should be verified for thermal insulation materials using thermal conductivity values derived as outlined in paragraph 0.3.2 above.
0.3.4 Thermal transmittance (U-value) relates to a building component or structure, and is a measure of the rate at which heat passes through that component or structure when unit temperature difference is maintained between the ambient air temperatures on each side. It is expressed in units of Watts per square metre per degree of air temperature difference (W/m2K).
0.3.5 Thermal transmittance values (Uvalues) relevant to this Part of the Regulations are those relating to elements exposed directly or indirectly to the outside air. This includes floors directly in contact with the ground, suspended ground floors incorporating ventilated or unventilated voids, and elements exposed indirectly via unheated spaces. The U-value takes account of the effect of the ground, voids and unheated spaces on the rate of heat loss, where appropriate. Heat loss through elements that separate dwellings or other premises that can reasonably be assumed to be heated, is considered to be negligible. Such elements do not need to meet any particular U-value nor should they be taken into account in the calculation of CO2 emissions or overall transmission heat loss.
0.3.6 A range of methods exist for calculating U-values of building elements. Methods of calculation are outlined in Appendix A, together with examples of their use. Alternatively U-values may be based on certified measured values. Measurements of thermal transmission properties of building components generally should be made in accordance with I.S. EN ISO 8990: 1997, or, in the case of windows and doors, I.S. EN ISO 12567-1: 2001.
0.3.7 Any part of a roof that has a pitch of 70o or more may be treated as a wall for the purpose of assessing the appropriate level of thermal transmission. Elements separating the building from spaces that can reasonably be assumed to be heated should not be included.
0.3.8 Appendix B contains guidance on the construction and installation for common forms of construction for roofs, walls and floors. It explains the condensation risk and gives guidance on the use of vapour control layers. Table B1 in Appendix B contains indicative U-values for external doors, windows and rooflights (roof windows).
Dimensions
0.4.1 Except where otherwise indicated linear measurements for the calculation of wall, roof and floor areas and building volumes should be taken between the finished internal faces of the appropriate external building elements 10 and, in the case of roofs, in the plane of the insulation. Linear measurements for the calculation of the areas of external door, window and rooflight openings should be taken between internal faces of appropriate sills, lintels and reveals.
0.4.2 “Volume" means the total volume enclosed by all enclosing elements and includes the volume of non-usable spaces such as ducts, stairwells and floor voids in intermediate floors.
Definitions
For the purposes of this Technical Guidance Document the following definitions apply: -
Energy Use (for a particular purpose, e.g. space heating, water heating, cooling, ventilation, lighting): Energy input to the relevant system to satisfy the relevant purpose.
Delivered Energy: Energy supplied to the dwelling and its systems to satisfy the relevant energy uses, e.g. space heating, water heating, cooling, ventilation, lighting. Delivered energy does not include renewable energy produced on-site.
Delivered energy differs from energy use by the extent of on-site conversion and transformation losses, e.g. boiler efficiency losses.
Primary Energy: Energy that has not been subjected to any conversion or transformation process. For a dwelling, it is the delivered energy plus the energy used to produce the energy delivered to the dwelling. It is calculated from the delivered energy, with an allowance for any energy exported from the site, using conversion factors.
Renewable Energy: Energy from renewable non-fossil energy sources, e.g. solar energy (thermal and photovoltaic), wind, hydropower, biomass, geothermal, wave, tidal, landfill gas, sewage treatment plant gas and biogases.
Biomass: Biodegradable fraction of products, waste and residues from agriculture (including vegetal and animal substances), forestry and related industries, as well as the biodegradable fraction of industrial and municipal waste, used as a fuel or energy source. Fuels derived from biomass may be in solid, liquid or gas form. In this document, where the term “biomass” is used on its own, it should be taken to mean solid biomass (wood, wood chip, wood pellet, etc).
Biofuel: Liquid or gas fuel derived from biomass.
Seasonal Efficiency: The seasonal efficiency calculated as defined in the DEAP manual.
Note: Biomass (including biofuel) is generally included in Delivered Energy and thus, together with the energy used to produce and deliver it, included in Primary Energy.
Application to Buildings of Architectural or Historical Interest
0.6.1 Part L does not apply to works (including extensions) to an existing building which is a “protected structure” or a “proposed protected structure” within the meaning of the Planning and Development Act 2000 (No. 30 of 2000).
0.6.2 Nevertheless, the application of this Part may pose particular difficulties for habitable buildings which, although not protected structures or proposed protected structures, may be of architectural or historical interest.
0.6.3 Works such as the replacement of doors, windows and rooflights, the provision of internal and/or external insulation and damp-proofing to walls and basements, insulation to the underside of slating and provision of roof vents and ducting of pipework could all affect the character of the structure.
0.6.4 In general, the type of works described above should be carefully assessed for their material and visual impact on the structure.
0.6.5 Historical windows and doors should be repaired rather than replaced, and internal insulation and damp-proofing should not disrupt or damage historic plasterwork or flagstones and should not introduce further moisture into the structure.
0.6.6 Roof insulation should be achieved without damage to slating (either during the works or from erosion due to condensation) and obtrusive vents should not affect the character of the roof.
0.6.7 In specific cases, relaxation of the values proposed may be acceptable, to the local building control authority, if it can be shown to be necessary in order to preserve the architectural and historical integrity of the particular building.
0.6.8 For more guidance on appropriate measures see “Guidelines No 9: Architectural Heritage Protection - Guidelines for Planning Authorities” and “Energy Efficiency in Traditional Buildings” by the Department of the Environment, Heritage and Local Government.
Nearly Zero Energy Buildings (NZEBs)
0.7.1 In accordance with Directive 2010/31/EU of the European Parliament and the Council of 19 May 2010 on the energy performance of buildings (recast), all new dwellings will be nearly zero energy dwellings by 31 December 2020.
0.7.2 Nearly Zero Energy Building means a building that has a very high energy performance, as determined in accordance with Annex I to Directive 2010/31/EU of the European Parliament and the Council of 19 May 2010 on the energy performance of buildings (recast)(O.J. No. L 153, 18.6.2010, page 13). The nearly zero or very low amount of energy required should be covered to a very significant extent by energy from renewable sources, including energy from renewable sources produced on-site or nearby.
0.7.3 In order to achieve the acceptable primary energy consumption rate for a nearly zero energy dwelling, the calculated energy performance coefficient (EPC) of the dwelling being assessed should be no greater than the Maximum Permitted Energy Performance Coefficient (MPEPC). The MPEPC for a nearly zero energy dwelling is 0.30.
0.7.4 To demonstrate that an acceptable CO2 emission rate has been achieved for a nearly zero energy dwelling, the calculated carbon performance coefficient (CPC) of the dwelling being assessed should be no greater than the Maximum Permitted Carbon Performance Coefficient (MPCPC). The MPCPC for a nearly zero energy dwelling is 0.35.
