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This page explains the abbreviations and jargon used in regard to energy assessments. |
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A Domestic Energy Assessment is a standardised method that has been devised so anybody can compare the energy efficiency of a domestic dwelling. It calculates from the information taken at the time of the assessment, the energy required to heat the property, the hot water and for lighting, to a standard level regardless of occupancy. The assessment assumes a standard heating level of 9 hours during the week and 18 hours at the weekend and a given temperature of 21°C in the living room and 18°C in all other rooms. The figure calculated between 1 to 100 is a measure of the cost for heating and lighting in £ per square metre, the higher the rating the lower the cost. A figure of 1 = £10/sq m/year or more and a figure of 100 means that the property has zero energy input. Most houses fall into a SAP band between 30 to 80 with a cost £/sq m ranging from £6.00 down to £1.60. |
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The Reduced data Standard Assessment Procedure is the method that is used by all Domestic Energy Assessor to assess domestic property. This involves taking a number of measurements and making specific observations of the property. This will require access to the roof space, boiler, hot water cylinder, heating controls and all the rooms in the property.
New properties being purchased from a builder do not require a RdSAP by a Domestic Energy Assessor as a Full SAP will be supplied by the builder which has been calculated at the time of construction. |
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The Environmental Impact Rating (EIR) is produced from the information taken and it is a measure of how much Carbon Dioxide is produced annually from heating and lighting the property. Different fuels have a marked effect both on the SAP and the EIR rating. Mains gas has a lower cost and reduced Carbon Dioxide emission compared to heating with electricity.
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Carbon Dioxide, chemical formula CO2, is a major by-product when fossil fuels are burnt. It is released to the atmosphere and is one of the greenhouse gases that is having an adverse environmental effect. Domestic energy consumption accounts for a third of all CO2 produced in the UK and the Government has a commitment to reduce Carbon Dioxide emissions by 60% by 2050.
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A Domestic Energy Assessor or DEA for short, is licensed on behalf of the Government to undertake Domestic Energy Assessments and together with Home Inspectors, are the only people allowed to produce Energy Performance Certificates (EPCs) for domestic property (other than new build). A DEA has to undergo specific and ongoing training and must meet a given standard before they are accredited. This ensures that all EPCs are of a given standard which allows houses to be compared easily with regard to their energy efficiency. |
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An Energy Performance Certificate or EPC is produced once all the data has been submitted by the Domestic Energy Assessor. The EPC is produced electronically using special standardised software, giving the current SAP rating together with the current Environmental Impact Rating (EIR). The software also produces a number of suggested measures which the property owner may wish to pursue, together with likely costs and what effect these measures will have on reducing energy costs, SAP and EIR ratings.
Once the EPC has been produced it is held on a central database run by Landmark, for and on behalf of the Government, with a copy of the certificate being sent to the person who requested the Energy Assessment. |
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SBEM is a computer program developed by the Buildings Research Establishment (BRE) that provides an analysis of a building's predicted energy consumption based on the structure, heating, ventilation, cooling and lighting systems of the building. The SBEM tool is designed to cover buildings that are not dwellings and has been adopted by government as part of the UK national calculation methodology (NCM) for calculating the energy performance of non domestic buildings. It is used to assess commercial buildings that are classed as being Level 3 and 4 buildings and to demonstrate compliance with Part L of the Building Regulations (in England and Wales).
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Part L of the Building Regulations 2000 (in England and Wales.) are the regulations that new and refurbished buildings must meet in regard to the conservation of fuel and power. Parts L1A and L1B covers new and refurbished dwellings, whilst parts L2A and L2B covers new and refurbished commercial properties. It lays down insulation standards, plant and lighting efficiencies to which the building must meet. |
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A Non Domestic Energy Assessor, a NDEA for short, is licensed on behalf of the Government to undertake Commercial Energy Assessments and are the only people allowed to produce Non Domestic Energy Performance Certificates (NDEPC) for both new and refurbished buildings. A NDEA has to undergo specific and ongoing training and must meet a given standard before they are accredited. This ensures that all NDEPCs are of a given standard and different buildings can be easily compared with regard to their energy efficiency. |
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A Display Energy Certificate, known as a DEC, is an Operational Rating of a building which shows the actual annual energy consumption and gives a comparative rating to the building. Also shown on the DEC are the two previous years’ energy consumption and any power generated by Low or Zero Carbon technology (LZC). All government buildings larger than a 1000m² and regularly visited by the public must displayed a DEC in the public area of the building. |
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Low or Zero Carbon Technologies are now being used to generate or use energy much more efficiently. Zero Carbon technologies include Solar Water Heating, Wind Turbines and Photovoltaic Panels which generate electricity from sunlight. Low Carbon technologies include air, ground and water source Heat Pumps, Low Energy Lights (LEL), Combined Heat and Power plants, Tri-Generation, Bio-Mass boilers and Evaporative Chillers. Most are already being used in commercial buildings and now EPCs for domestic buildings are recommending some of these technologies to improve energy efficiencies.
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Renewable Energy is the name used to describe the generation of energy from natural sources and includes Solar and Thermal Water Heating, Wind Turbines, Photovoltaic Panels, Wave Power, and Hydroelectric Power. These technologies are being increasingly used to reduce carbon emissions, but their initial capital costs are high which means they have a long payback period.
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A Dynamic Simulation Model is a software tool that models energy inputs and outputs for different types of large complex commercial buildings, such as London’s Swiss-Re (Gherkin) building. In certain situations, SBEM, will not be sophisticated enough to provide an accurate assessment of a building's energy efficiency and in these cases Government-approved proprietary dynamic simulation models may be used. These buildings are classed as Level 5 buildings and may only be assessed by an accredited Level 5 (NDEA) commercial energy assessor.
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A Commercial Energy Performance Certificate or NDEPC is required whenever a commercial building is sold, let or modified (major extensions). A building is defined as having walls, a roof and the internal spaced is conditioned. The only exceptions are buildings which are:
Places of worship. Detached commercial property of less than 50m². Industrial sites and workshops with low energy demand. Agricultural Buildings. Temporary buildings which have a life span of less than 2 years. Buildings which are derelict. Buildings which are to be demolished for development, but the vendor must be able to prove this.
NDEPCs are much more complex and time consuming to produce compared with an EPC. A building must be broken down in zones and each must be attributed with an activity. Every wall in each zone must be measured and its construction identified, all floors, ceilings, windows and doors must be detailed along with the lighting and HVAC system for each zone. Once all relevant information has been collected it is entered into the SBEM or DSM software and the NDEPC is generated.
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There are three levels of building classification used in Commercial Energy Assessments. Level 3: Any size of building but must have a boiler size (heat input) no greater than 100kW and comfort cooling no greater than 12kW. Level 4: New buildings that need to be signed off for building control to confirm it complies with Building Regulations part L. All other commercial buildings subject to SBEM being capable of giving a meaningful result. Level 5: Complex buildings that require Dynamic System Modelling. Assessors must be accredited to the given level to assess the building.
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SAP: Standard Assessment Procedure Introduced in 1998 as the methodology used to assess new dwellings with regard to energy efficiency and carbon emissions. SAP1998 and SAP2001 used a Carbon Index (CI) which together with given U-Values for specific thermal elements determined the efficiency of the building. SAP2005 introduced the Target Emission Rate (TER) and Dwelling Emission Rate (DER) which replaced the Carbon Index and together with more flexibility in U-Values of thermal elements (see Part L of Building Regulations) allows for the greater reduction in carbon emission to be achieved. SAP 2009 will be fully implemented from April 2011 following the amendments to the Building Regulations introduced in October 2010. Further revisions to SAP are expected in 2012 and 2015. |
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Accredited Construction Details (ACD) have been developed to help achieve the performance standards required to demonstrate compliance with the energy efficiency requirements (Part L) of the Building Regulations.
The details focus on the issues of insulation continuity (minimising cold bridging) and airtightness. They are not intended to provide any detailed guidance on other performance aspects such as vapour control and ventilation. The Accredited Construction Details contain checklists which should be used by the Designer, Builder and Building Control to help demonstrate compliance.
Steel frame illustrative detail Timber frame illustrative detail Masonry cavity wall insulation illustrative detail Masonry inetrnal wall insulation illustrative detail Masonry external wall insulation illustrative detail
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K-Value: the measure of Thermal Conductivity Also known as a Lambda Value (λ) is the measure of the amount of heat (Watts) transmitted through a unit of area (square metres) of a material of unit thickness (in metres) for a unit of temperature difference (in degrees Kelvin/Celsius) between inside and outside environments, expressed as W/mK or W/m°C
R-Value: the measure of Thermal Resistance. It measures how well a particular thickness of material resists the flow of heat by conduction, the higher the figure the better insulation value. It is the reciprocal of thermal conductivity and is calculated in units of m²K/W or m²°C/W. The thermal resistance (R value) of a specific product can be found by dividing its thickness in metres by the λ value
U-Value: the measure of Thermal Transmittance. It measures the amount of heat transmitted per unit area of a particular thickness per unit temperature difference between the inside and outside environments. Calculated as W/m²K or W/m²°C.
The U-value is a composite measurement whereas the K-value is determined by the thickness of a single material. This is one of the reasons why the building regulations refer to U-values. The U-value of a building envelope (i.e. a wall) is the reciprocal of the sum of the thermal resistance of each element (brick, cavity, insulation, plasterboard, plaster) plus the internal and external thermal surface resistance.
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Air Pressure Testing to measure a buildings air permeability is a building regulation requirement for new buildings. This is done using specialist air testing equipment which pressurises a building and then measures the rate at which air leaks from the building. It is measured in cubic meters of air/ square meter of floor area/ hour, when pressured to 50 Pascals (Pa). The lower the score the more airtight the building is and the more thermally efficient.
New dwellings should aim to better 8.0m³/(h.m²)@50Pa but where a number of dwellings of the same type are built on a site then an average value may be taken plus the addition of 2.0m³@50Pa. On a small development the builder may choose not to under take an Air Pressure Test and a default value of 15.0m³@50Pa will be used in the SAP calculations to determine whether the property meets the Dwellings Emission Rate (DER).
In new commercial buildings and commercial extensions the aim should be to better 5.0m³@50Pa.
Compliance with the Building Regulations are met for both dwellings and commercial buildings when a pressure test of 10m³@50Pa or better is achieved, together with the property having a lower Dwellings Emmission Rate (dwellings)/Buildings Emissions Rate (commercial buildigs) than the Target Emmissions Rate.
Care at the time of construction to ensure that points where the building shell is punctured such as where waste pipes exit a building are properly sealed, will help minimise air leakage. |
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Target Emission Rate The Target CO2 Emission Rate (TER) is the minimum energy performance requirement for any new building. This is the target that all buildings must meet or exceed and it is calculate using SAP (dwellings) or SBEM (commercial buildings) software at the design stage from the plans. This is to show to Building Control that the proposed building is compliant with Part L of the current Building Regulations.
Dwelling Emission Rate The Dwelling CO2 Emission Rate (DER) is the actual energy performance of the dwelling that has been built and any alterations from the design stage to completion have to be entered into the SAP software along with the results of the air pressure test. If the DER is greater than the TER then the building will fail compliance and remedial action will have to be undertaken. This may mean reducing the buildings air permeability and repeating the Air Pressure Test or upgrading the heating controls or levels of insulation.
Building Emission Rate The Building CO2 Emission Rate (BER) is the actual energy performance of a commercial building that has been built and all alterations between the design stage and completion have to be entered into the SBEM software. Just as with DER, if the BER is greater than the TER then the building will fail compliance and remedial action will be required. |
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