The Dwelling Energy Assessment Procedure (DEAP) is the National Methodology for rating the energy efficiency of new dwellings in the Republic of Ireland. This ratings system was developed in response to EU Energy Performance of Buildings Directive’s intention to limit CO2 emissions caused by energy usage in buildings.
The methodology is designed to calculate and create Building Energy Rating (BER) certificates and to check compliance with Part L of the Building Regulations.
The significant outputs from DEAP include measuring Part L compliance under ‘overall heat loss’ or ‘elemental method’, it calculates carbon emissions (CDER) and compares to a reference dwelling (MPCDER), and calculates Primary Energy consumption in kwh/m2.annum leading to a Primary Label with scale A-G. DEAP calculates CO2 emissions expressed as tons / dwelling leading to a Secondary Indicator, and also calculates indicative values for fuel costs/annum based on standard fuel prices compiled and updated by SEI.
The calculation is based on the following criteria:
• size, geometry and exposure of the dwelling
• materials used for construction
• 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
• 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 energy generation
In this article we look at some of the principal factors that impact on the BER. This has been done through the use of a case study example in which the main energy using elements are varied and the results tabulated.
Please note that this is a preliminary and limited study of a complex method that has only very recently been introduced. That said hopefully, in the space available, we can highlight some of the principals at work in the calculation method.
HEATING AND HOT WATER
As mentioned, DEAP is linked to compliance with Part L of the Building Regulations, ‘Conservation of Fuel and Energy’. We found that once building envelope compliance was achieved then perhaps the most important aspect in setting out to get a good BER is the method used for space and water heating. That is not to say that ‘Passive Design’ principals that go beyond minimum construction standards for insulation, reduced glazing areas and so on is not also a worthwhile avenue of exploration for an improved BER. For most standard dwellings however, built for the mass market, the indications were that boiler efficiency and good control of heating and hot water are key to gaining ground in DEAP.
DEAP also requires, in most cases, that a secondary heating system is specified. We found that the efficiency and fuel used for this also has a very important effect on the BER. In Appendix A1 of the DEAP manual it is stated that ‘a secondary heating system is to be specified where fixed secondary heaters are present’. Secondary heaters would include an open fireplace, a gas fire (either in chimney, catalytic or balanced flue type), electric fuel effect fire (for instance set into mock fireplace or modern design set into the wall), a wood pellet, log, multifuel or oil fired stove, any other fixed appliance heating the living room, and electric heaters to be assumed where storage heaters are used.
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