Eco-Build NW - Construction flows

Analysis of resources, waste and impacts in the construction process

Resource flows in housing

The average house in the North West has a distinct profile:

  • 2.35 people living in it, 0.4 cats and 0.3 dogs
  • It consumes 9,127 KWh of energy, producing 5.18 tonnes of CO2 per year
  • It weighs about 150 tonnes, with another 140 tonnes for the foundations
  • It requires 0.50 tonnes of materials each year for maintenance and repair
  • Most of the energy is derived from natural gas (66%) and electricity (24%)

The charts show the flow of materials into a house required for maintenance and maintenance as well the energy required on a yearly basis to provide space heating, hot water, lighting and energy for appliances and cooking.

Of the 150 tonnes required to build the average house, the majority is made up of concrete and stone. Over the 60 year lifetime of the building, theoretically, 4.8 tonnes of materials are consumed each year. An extra 0.50 tonnes is required on an annual basis to maintain the condition of the house and build extensions etc. Therefore, in total the average house requires 5.3 tonnes of products a year.

Construction and manufacture of all the building materials for a typical dwelling produces an average 61 tonnes of CO2. When disaggregated over the lifetime of the buildings, the CO2 impact is approximately 1-2 tonnes per year, depending on the assumed life and whether a depreciation calculation is used. The yearly emissions of CO2 emissions from maintenance and repair add another 0.19 tonnes of CO2, or 10-20%. However, the most significant emissions come from the operational use of the house. The direct energy (gas, electricity and other fuels) produces an average of 5.38 tonnes per year, a total of 6.57 tonnes CO2 per house, per annum.

The chart here shows the effect of spreading the construction impact over a shorter or longer building lifetime. At the same time, energy and maintenance impacts also rise gradually with building age. The optimum point is about 30 -40 years, similar to that using a NPV calculation at 6% discount.