How cold can you go? Is 16°C reasonable?

As we enter a cold snap, and energy prices have risen again, we are more worried about how to manage our home heating. The easiest way to reduce bills is to turn down the thermostat. Do we really need 20°C or higher at home? Perhaps this is merely a social convention. David MacKay published ‘Sustainable Energy Without the Hot Air’ in 2009, in which he proposed turning down the thermostat at home to 16°C to reduce carbon emissions. At his publicity talks he explained how his household (with wife and two children) had successfully adapted to these conditions. He also incorporated the 16°C target in the 2050 calculator for scenario planning for net zero. This was the extreme level for one of the home energy 'levers'.

I find this idea scary; thick jumpers do not seem to keep my hands warm – even at 19°C I find my fingers stiffen so that I struggle to type unless I wear half-fingered gloves. I know many people are forced to endure such conditions through fuel poverty but I cannot imagine doing it from choice. Is this reasonable?

So I was intrigued to read about a group of 23 people in Belgium who decided to experiment with heating at home – can they turn down the setpoint on the thermostat and heat the body instead, generating less carbon emissions while still enjoying their living conditions and avoiding any ill effects? [1].

By the third season some were comfortable with the mean living room temperature as low as 14°C.

How much to disconnect your gas supply?

 

When you decarbonise your home by going electric, you can save more money by going off gas completely so as to avoid the standing charge (the fixed annual charge). In my region, this can save up to £115/year but in some places you can save twice as much [1].

To avoid the standing charge you have to get your meter removed. The meter is owned by the supplier and you have to get them to do this – DIY or Fred Bloggs the engineer are not allowed. The supplier charges are highly variable, from £0 to £100s or even more. For example, this story Why does gas supplier charge £486 to remove meter when others do it free? (Guardian) details a charge of £486 to disconnect a Quaker Meeting House.

These charges are a disincentive to changing to a heat pump. Paying the annual fixed charge can tip the balance between paying more for low carbon heating or less. However, paying the meter removal charge adds to the upfront cost which is already steep.

Some recommendations based on actual experience.

I asked my friends (in Transition Cambridge Energy Group) about their experiences of disconnecting. These are all anecdotes and I have omitted names. 

Solving under-occupancy with ‘adjustable housing’

One of the best ways to save energy is to move to a smaller house. Heating a larger house takes a larger amount of energy – floor area accounts for 70% of variation in space heating demand, as modelled by the CHM [1]. According to the Bedroom Standard (see below), 4.4% of homes are over-crowded but 69% are under-occupied [2]. If you allow one spare room then that number reduces to about 36% but that is still a lot! If everyone lived in a home the right size, we would overall need less heating energy. Obviously this is a hopeless ideal – but could we get some of the way there?

What’s wrong with water softeners?

Cambridge has hard water and it scales up our appliances. Some of them we can clean with a bit of effort, but some are not so easy. You can clean the heating element in your kettle just by soaking in hot dilute vinegar – but getting at the heat exchanger in your hot water cylinder is a tricky job. The obvious answer is a water softener. 

There are two problems.

1. Water softeners use extra water and we are already water stressed in this area.
2. Water softeners use a lot of salt and this is bad for the environment. It has to go somewhere: usually it ends up in our rivers.

How bad is this and what can we do about it?

Learnings from monitoring the solar hot water system

For reasons too complicated to explain (best summarised – if I was you I would not start from here) my beloved has implemented a controller for our solar thermal pump. This is for a solar thermal panel, rather than a solar electricity panel. The pump circulates hot water (with glycol) from the panel to the hot water cylinder and back. Knowing my love of data he added some monitoring into this system and we have been poring over the charts. Here is one from a reasonably sunny day.

Monitored temperatures on a sunny day (times in GMT)

Travel emissions per hour

How do you think of travel distances in your head? People often think in terms of the time taken to get there rather than the actual distance. One hour (each way) is not unusual for regular commute by car and for a weekend excursion you might think three hours was reasonable. By air you can get quite a long way in three hours. Here I compare GHG emissions for various travel modes by km and by hour. 

This post was inspired by some much prettier graphics from the Visual Capitalist showing emissions per km. I have come to think that metric is positively misleading. 

How to grow climate friendly food at home

Were you as shocked as I was to hear that growing your own food at home has six times the GHG emissions as conventional agriculture? Surely it does not have to be like this? I looked at the study behind the news [1]. (It came out in January and I do not understand why it has hit the news again now.) The good news is, the main sources of emissions from home grown produce are easily avoided, with a bit of care. 

Compost heaps were one of the main sources of GHG emissions from urban gardens - but good practice can minimise this.