Targeting household energy-efficiency measures using sensitivity analysis

Abstract

The Community Domestic Energy Model (CDEM) has been developed to explore potential routes to reduce CO 2 emissions and the model is used to predict the CO 2 emissions of the existing English housing stock. The average dwelling CO 2 emissions are estimated as 5,827 kgCO 2 per year, of which space heating accounts for 53%, water heating 20%, cooking 5% and lights and appliance 22%. Local sensitivity analysis is undertaken for dwellings of different age and type, to investigate the effect on predicted emissions of uncertainty in the model's inputs. High normalised sensitivity coefficients were calculated for parameters that affect the space heating energy use. The effects of the input uncertainties were linear and superposable, so the impact of multiple uncertainties could be easily determined. The results show that the accumulated impact on national CO 2 emissions of the underperformance of energy efficiency measures could be very large. Quality control of the complete energy system in new and refurbished dwellings is essential if national CO 2 targets are to be met. Quality control needs to prioritise detached dwellings because their emissions are both the greatest and the most sensitive to all energy efficiency measures. The work demonstrates that the uncertainty in the predictions of stock models can be large; failure to acknowledge this can lead to a false sense of their reliability.

Turning lights into flights: Estimating direct and indirect rebound effects for UK households

“…Cavity wall insulation: We estimate that individual dwellings eligible for cavity wall insulation have a mean net wall area (after subtracting glazing and door areas) of 67.3m 2 and a mean cavity width of 65 mm (Firth et al, 2009 Loft insulation: We estimate that individual dwellings eligible for top-up loft insulation have a mean roof area of 45 m² and a mean thickness of existing insulation of 0.149m (Firth et al, 2009;Johnston, 2003). Topping up existing insulation to 270 mm is assumed to require 5.45m 3 of mineral wool of density 25 kg/m 3 and embodied GHGs of 1.28kgCO 2 e/kg (Hammond and Jones, 2011), leading to 174 kgCO 2 e of embodied GHGs for an eligible dwelling.…”

“…Approximately one fifth of the existing boiler stock is condensing (Firth et al, 2009), but the premature replacement of an existing boiler before the end of its natural life is unlikely to be economic. 23 We therefore assume the natural replacement of existing boilers at the end of their life and assume that the incremental embodied GHGs are zero.…”

“…The CDEM model has been developed by Firth et al (2009) at Loughborough University to simulate energy use in the English housing stock and to explore options for reducing CO 2 emissions. The CDEM is one of a family of bottom-up, engineering models of the English housing stock that are based upon algorithms originally developed by the UK Building Research Establishment (Kavgic et al;Shorrock and Dunster, 1997).…”

“…We use an engineering model (Firth et al, 2009) to estimate the direct energy consumption of the English dwelling stock by year (t=1 to T) and energy carrier (f). The relevant energy carriers are gas, oil, solid fuels and electricity.…”

Review on stochastic modeling methods for building stock energy prediction

“…In the UK, several residential building stock models used BREDEM (building research establishment domestic energy model) (Anderson et al 1985) as a core calculation engine for single houses to predict energy use for each archetype (Shorrock and Dunster 1997;Jones et al 2000Jones et al , 2007Johnston 2003;Boardman et al 2005;Boardman 2007;Natarajan and Levermore 2007a,b;Firth et al 2010). More detailed comparisons of UK models were discussed in Kavgic's review (Kavgic et al 2010) and Oladokun's review (Oladokun and Odesola 2015).…”