The Road to Carbon-Zero 2011 – The First Steps

Overview

In 2005, before consciously reducing my carbon footprint, the house was extensively refurbished. The front and patio doors were replaced with new standard PVCu units with thermal values of the time, the side door was removed and bricked up, the flat roof extension roof was replaced, re-insulated and covered with a rubber membrane, the loft was insulated to 150 mm with wool fibre and the old inefficient boiler was replaced with a 90% efficient gas condensing boiler, new pipework, and radiators. This improved the thermal efficiency of the building when compared to the baseline year. The electrics were rewired and there were also new electrical additions in the form of a desktop PC and a dishwasher, and an old washing machine was replaced.

In 2011, the first low-cost measures were introduced to further improve the thermal efficiency of the building and its energy and water consumption. The carbon fingerprint is shown in Fig.1. in comparison to the baseline. 

Fig.1. The fingerprint of CO₂e emissions in 2011, in comparison with the baseline.

Household Electricity Consumption

Initially, an energy monitor was used to find where consumption could be reduced. LED bulbs were installed throughout the house which use 90% less power than the incandescent or halogen bulbs they replaced. Investments were made in an eco-kettle which can boil just a single cup, and a slow cooker. Effort was also made to ensure appliances were never left on standby.

Total annual household electricity consumption was slightly reduced by 2% to 1739 kWh, derived from a utility bill for that year. All consumption was provided by the electricity grid and given a carbon intensity figure of 0.491 kgCO₂e/kWh (DECC, 2013) for a 2011 generation mix. This resulted in a reduction of 65 kgCO₂e to 854 kgCO₂e, holding the fingerprint value at 0.9 tCO₂e emissions.

Space and Water Heating

To further reduce building fabric heat loss, loft insulation was increased to 300 mm with wool fibre, and cavity wall insulation was installed. Areas where air was escaping, gaps under skirting boards for example, were also sealed. Importantly, the insulation was funded by a Welsh Government grant available at the time, which was much appreciated.

These measures reduced total annual household gas consumption by 61% to 6127 kWh, again derived from a utility bill for that year. All consumption was provided by the gas grid and given a carbon intensity figure of 0.206 kgCO₂e/kWh (DECC, 2012). This resulted in a reduction of 1973 kgCO₂e to 1262 kgCO₂e or 1.3 tCO₂e emissions.

Car Travel

The vehicle in use was a mid-sized 2.0 litre petrol. The estimated annual mileage to the nearest 1000 was given as 8000 miles, or 13000 km. The carbon intensity figure of petrol fuel production and use is given as 0.249 kgCO₂e/km (DECC, 2012). This resulted in a 15% increase of 468 kgCO₂e to 3237 kgCO₂e or 3.2 tCO₂e emissions.

Water Consumption

At this time there was no water meter installed at the property. Some low-flow gadgets were installed on taps, and hippos placed in the two toilet cisterns. Total annual household water consumption was reduced by 24% to 38 m³, again derived from a utility bill for that year. The 2011 carbon intensity figure of domestic water supply (0.344 kgCO₂e/m³), and treatment (0.709 kgCO₂e/m³) is given as 1.053 kgCO₂e/m³ (DECC, 2012). This resulted in a reduction of 8 kgCO₂e to 40 kgCO₂e or 0.04 tCO₂e emissions.

Lifestyle

Conscious changes to my lifestyle began in this year.  Food was top of the list, I removed red meat and reduced dairy in my diet, started buying organic, fresh, seasonal food from local farm shops where possible, and only sustainably caught fish. I started supporting environmental charities Greenpeace, and Friends of the Earth, already a supporter of RSPB, and made much more effort to live by the three R’s, Reduce, Re-use and Recycle.

These changes were put into the carbon footprint calculator (WWF, 2016), and a figure was given for a low consumption lifestyle but with some conscious decisions around ethics and low-impact diet. This resulted in a 50% reduction to 0.5 tCO₂ emissions.

Infrastructure

The figure for infrastructure emissions in the carbon footprint calculator (WWF, 2016) remained at 2.75 tCO₂ for each UK citizen. However, whilst these emissions cannot be controlled directly, they can be off set through the natural sequestration of CO₂ through tree planting. This year I planted six native trees in the garden. The principle I use is that, according to the Woodland Trust, each tree will absorb one ton of CO₂ during a 100-year lifetime, which gives a value of 10 kg per year, although trees absorb more CO₂ as they mature and less in the early years. This gives a value of -0.06 tCO₂ in the fingerprint.

Behaviours

By this year the house was occupied most of the time, whilst I studied by distance learning from home, in contrast to occupancy in the baseline year. Because of this, there was inevitably some ‘rebound effect,’ as some of the energy efficiencies made were absorbed by increased consumption patterns.

Conclusions

There was an overall emissions reduction of 20% or 2.1 tCO₂e compared to the baseline year. This mostly came from the greater efficiency of the heating system, but also thermal improvements to the building fabric, through insulation and improved airtightness, with smaller contributions from lifestyle choices and water use. Electricity consumption was also reduced however the reduction was small due to increases in consumption from more appliances and hours of occupancy. Furthermore, the reduction in emissions would have been greater but were countered by the increased emission factor in the production and use of petrol for car fuel compared to diesel.    

References

The Department for Energy and Climate Change (2013). Greenhouse gas reporting – Conversion factors 2011. Available at: Greenhouse gas reporting – Conversion factors 2011 – GOV.UK (www.gov.uk) (accessed 05 August 2016).

The Department for Energy and Climate Change and The Department for Environment, Food and Rural Affairs (2012). 2012 Guidelines to Defra / DECC’s GHG Conversion Factors for Company Reporting. Table 1d. Available at: pb13773-ghg-conversion-factors-2012.pdf (publishing.service.gov.uk) (accessed 05 August 2016).

The Department for Energy and Climate Change and The Department for Environment, Food and Rural Affairs (2012). 2012 Guidelines to Defra / DECC’s GHG Conversion Factors for Company Reporting. Table 6b. Available at: pb13773-ghg-conversion-factors-2012.pdf (publishing.service.gov.uk) (accessed 05 August 2016).

The Department for Energy and Climate Change and The Department for Environment, Food and Rural Affairs (2012). 2012 Guidelines to Defra / DECC’s GHG Conversion Factors for Company Reporting. Table 9a. Available at: pb13773-ghg-conversion-factors-2012.pdf (publishing.service.gov.uk) (accessed 05 August 2016).

WWF-UK (2016). Available at: WWF Footprint Calculator (accessed 05 August 2016).