In the days when this lockdown status was looking inevitable, given what had gone on in other European countries, I had a conversation with a colleague about the impact of this on our carbon footprints. At first, we initially spoke about how much our carbon footprints would be reduced, if we all worked from home and stopped commuting. We then began to consider how other issues would impact this. Being at home all day, for some with children, would likely result in the whole home having to be heated to enable a home office / school; in turn increasing our carbon footprints. This got me thinking.
So, on this at-home bank holiday weekend I thought I’d estimate how a typical office, turned home workers carbon footprint may have increased / decreased over the past three weeks.
First item to address, commuting. Let’s assume this worker has a 20 mile commute each way in a petrol car. Using the governments conversion factor of 0.2249kgCO2e / mile, over the three weeks (giving them good Friday off) this equates to a 125.9kg reduction in carbon footprint due to home working.
The next item, heating, somewhat more complex to calculate. According to some internet search results the average floor area of a UK house is 104m2. By using this figure and by making some assumptions about the construction of our house we can estimate the heat loss rate for the building, a measure of how much heat is lost against the difference in internal / external temperature. Not being certain what is the UK average construction for houses I’ve assigned what I consider to be typical in UK houses.
- Uninsulated cavity walls of U Value 1.5 Wm-2k-1
- Windows and doors of U Value 2 Wm-2k-1 (accounting for 20% of wall space)
- Uninsulated roof of U value 1.5Wm-2k-1
- Floor of U value 1.2 Wm-2k-1
- 0.5 Air changes per hour
This gives a heat loss rate of 359.4Wk-1.
It is also necessary to make some very broad assumptions about the typical home workers heating system and how they use it both when working from home and when commuting. Largely based on my own preferences, let’s assume:
- Heating is only active when the external temperature drops below 15.5°C
- When working from home heating is on 06:00 – 22:00 everyday if required
- When commuting the heating is on 06:00 – 09:00 & 16:00 – 22:00 weekdays and 06:00 – 22:00 on weekends if required
- Home is kept at a toasty 20° C
- Heating is through gas boiler of efficiency 85%
- Whole property is heated
Now by looking back on weather data of the past three weeks, applying these rules and the heat loss rate, we can calculate how much heat our boiler is required to produce.
For the scenario where the worker is commuting as usual, this is 715.1kWh and 950.4kWh when working from home. Using the governments natural gas conversion factor of 0.20428 kgCO2e / kWh this equates to an increase of 48.1kg carbon emissions associated with heating.
This results in an overall net decrease of 77.9 kgCO2e. Looking back over the weather of the past three weeks I’m not surprised by this. So for comparative purposes, I used weather data for the same duration from the first full three weeks in February, this still resulted in a net decrease; albeit a less significant one of 38.3kg kgCO2e.
This is very approximate exercise including a lot of assumptions about commuting, buildings and their heating systems. It also excludes other variables that may have an impact on home energy consumption such as lighting, home IT equipment and increased brew making to name a few. For some of these the energy consumption and carbon emissions will not change but be accounted for by an individual’s carbon footprint rather than their employer. The take home from this is that the carbon emissions associated with commuting in an internal combustion car are greater than that associated with heating a home for a larger portion of the day. As such, I expect individuals carbon footprint will be overall slightly lower for this unique lockdown period.
So if nothing else this exercise makes for some mildly interesting carbon chat over a coffee when back in the office. Stay safe everyone.