Building Energy Rating (BER)
The EU’s Energy Performance of Buildings Directive (EPBD) was issued in 2002, aimed at improving energy performance in buildings (both new-build and existing) and required member states to introduce energy performance rating systems for all buildings.
The Directive was adopted into Irish law in 2006 and led to the introduction of Building Energy Rating (BER) certificate for all Buildings for Sale or letting after 1st Jan 2009.
Building Regulations : Part L Conservation of Fuel and Energy – Dwellings
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 (CO2) 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 and guidance on how to demonstrate compliance is provided in Technical Guidance Document L (TGD – L) Conservation of Fuel and Energy – Dwellings.
For new dwellings, the key issues to be addressed in order to ensure compliance are: -
1. LIMITATION OF PRIMARY ENERGY USE AND CO2 EMISSIONS
The methodology for calculation primary energy consumption and CO2 emissions 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. 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 (kgCO2/m2/yr).
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, 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.
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 0.4;
- 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 0.46.
The DEAP software will calculate the EPC and CPC of the dwelling being assessed and clearly indicate whether compliance with the requirements of the Regulations has been achieved.
2. RENEWABLE ENERGY TECHNOLOGIES
The following minimum level of energy provision from renewable energy technologies is required to satisfy the Regulations :
- 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.
3. FABRIC INSULATION
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 the table below (both 2007 & 2011 requirements are shown to illustrate the effects of the 2011 revision).
The performance levels specified above represent the minimum performance levels so as to ensure reasonable levels of performance. Meeting the performance levels shown above will not necessarily mean that the level specified for primary energy consumption and related CO2 emissions will be met. One or more of the performance levels specified will need to be exceeded to achieve this.
4. THERMAL BRIDGING
To avoid excessive heat losses and local condensation problems, 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. 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 using the Psi values associated with the specific details adopted.
5. BUILDING ENVELOPE AIR PERMEABILITY
To avoid excessive heat losses 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.
Air pressure testing should be carried out on a proportion of dwellings on all development sites and the test results used in DEAP calculations.
When tested a performance level of 7 m3/(h.m2) represents the 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.
6. BUILDING SERVICES
The regulations require that space and water heating systems in dwellings be energy efficient, with efficient heat sources and effective controls. More specifically oil or gas fired boilers must achieve a minimum seasonal efficiency of 90%.
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.
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
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. Pipes and ducts which are incorporated into wall, floor or roof construction should be insulated.
Mechanical ventilation systems
Where a mechanical ventilation system designed for continuous operation (with or without heat recovery) is installed for the provision of ventilation to a dwelling, the system should 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 : www.sap-appendixq.org.uk.
The effectiveness of mechanical ventilation systems improve as air permeability values decrease. Air permeability values of less than 5 m3/(hr.m2) at 50 pa are recommendedin dwellings with mechanical ventilation, especially ventilation systems with heat recovery.
7. CONSTRUCTION QUALITY AND COMMISSIONING OF SERVICES
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.
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.