40% House

Introduction

The 40 percent house project is the result of a two and a half year research programme focusing on how to make deep cuts in carbon emissions whilst successfully meeting household energy needs.

The 40 percent house scenario for 2050 is one in which all householders have more space, heat, hot water and lighting and appliances.

The project demonstrates that the domestic sector can deliver on the four key principles of the 2003 Energy White Paper:

# A 60% reduction in carbon dioxide (CO2) emissions by 2050.

  1. The provision of adequate and affordable warmth for all.
  2. Security of energy supply.
  1. The development of a competitive energy industry.

    Under the 40 percent house scenario, these principles are all met with measures within the housing stock. There is no reliance on external energy supply ‘fixes’, such as reliance in the future on low carbon electricity generated from remote renewable or new nuclear power stations. The 40 percent house achieves a transformation of the housing stock and in the process creates a multitude of business opportunities for the provision of low carbon solutions.

    The domestic sector is a critical area to focus on: it consumes 28% of all energy generated and is responsible for 27% of UK CO2 emissions (DTI 2002, DEFRA 2002). Energy demand in the sector grew 17.5% from 1990 to 2003 – higher than the 7.5% growth for the economy as a whole during the same period.

    The domestic sector is responsible for approximately a third of all energy use and consequent carbon dioxide emissions in the UK economy.
    Source: DTI and DEFRA (2002)

    There are many factors affecting energy consumption in the sector, including population size, household size, building fabric, and lighting and appliances. Population and household size are two factors with significant implications for energy demand but are difficult to influence through policy intervention. Mid-range projections from the Government’s Actuary’s Department (GAD) indicate that by 2050 the UK population will have increased to 66.8 million people compared to 60 million now. The age structure of the population will change considerably with the proportion of people over 65 years old increasing from approximately a fifth now to a peak of 25% in 2060.

    Household size is one of the main driving forces behind the growth in energy demand for the domestic sector. Per capita energy consumption tends to plummet when people live in larger households because of shared energy services. There are a number of inter-related factors influencing household size, including income, house prices, availability of housing and age of residents. The average household size has been falling for some time: in 2004 there were 2.4 people per dwelling. The proportion of one-person households rose from 18% in 1971 to 29% in 2001 in Great Britain (NS, 2004). This trend is expected to continue therefore the 40 percent house project assumes 2.1 people per dwelling by 2050.

    The trend to smaller households is a key factor increasing energy consumption because of the economies of scale
    Source: Fawcett et al. (2000)

    Since 1970, energy use per household has changed very little but because of a substantial growth in household numbers overall energy consumption has increased by 32%. The main areas of energy demand are space heating, accounting for 60% of energy use, followed by hot water heating (25%) and lighting and appliances (15%). In the last thirty years gains in energy efficiency have been offset by an increase in comfort and an increase in electricity for lights and appliances.

    Residenital energy use and savings from 1970 to 2000
    Source: Based on Shorrock and Utley (2003)

    In summary, given the trends towards more people, smaller household size and higher energy use in the home, current policies are failing to deliver significant cuts in CO2 emissions from the domestic sector.

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