Tuesday, 29 October 2013

Adding to the living room temperature debate

Last weekend the government released a new Cold Weather Plan which advises us all to keep our living rooms to 21°C or warmer during the day [1]. Given the recent increases in energy prices, this is a pipe dream for some people and is inconsistent with other advice we have been given.  For example, the Energy Saving Trust says 'Your room thermostat should be set to the lowest comfortable temperature - typically between 18°C and 21°C' [2]. There is a big difference between 18°C and 21°C - and potentially a 20% difference in fuel bills. So what is a reasonable temperature, for the living room and for the other rooms in your house?

I know people who claim to be comfortable with the thermostat set to 15°C but they are definitely in the minority. I have posted on this subject before - What is a reasonable setting for my thermostat - and there is evidence that many people, even among the elderly, feel comfortable at 18°C wearing conventional winter clothing. The Cold Weather Plan does not give any justification for the figure of 21°C as a minimum for rooms occupied during the day. It also recommends 18°C as a minimum for night time bedroom temperature which it says has 'no health risks, though occupants may feel cold'. I checked the regulations from the Health and Safety Executive[3] about suitable temperatures and they say the minimum for a work room should be at least 16°C, or 13°C if there is significant manual labour involved.

However, 18°C is too cold for many people who are vulnerable for some reason. For example, most people if they feel cold will get up and stand by the radiator for a bit or walk around, make themselves a hot drink and so on. If you can't do this, particularly if you can't exercise at all, then that makes you very vulnerable to the cold. I remember when my mother was alive but in a wheelchair she was extremely prone to cold legs and feet, even under the thickest of blankets. It doesn't matter how well you insulate your body if your body isn't generating any heat. As for the bedroom temperature, 18°C allows for the worst situation where someone has a fall during the night and can't get back into bed. At 16°C this would exacerbate a chest infection. At 12°C it could trigger heart failure. At 5°C they could die of hypothermia before morning. However, most people are unlikely to fall over in the first place.

I find it significant that on the 'Action Card for Individuals' part of the Cold Weather Plan [1] there is no mention of the 21°C requirement until a level 3 event which is an external temperature of 2°C or less. I think the key point here is that 21°C will enable you to warm up quickly after you come in very cold from being outside. 

In any case, you don't need to heat your whole house to 21°C, only the room(s) you are in (see also How much of your house do you heat?) How can we do this? To start with you will need thermostatic radiator valves for each room. Also, in many houses the thermostat is in the hall which is not a room we spend a lot of time in. Is it any wonder some people use the thermostat as a switch, turning it up and down to turn the heating on and off? A portable wireless thermostat can help. 

Another option is to turn the central heating right down, or off, and just run a fire in one room.  However, the savings may be not as great as you might expect. If you have gas central heating with an efficient boiler and you turn that down in favour of an electric fire, then you must bear in mind that the gas costs you a third as much as the electricity for the same heat. A gas fire isn't necessarily any better either: if it is the sort with an open flue then most of your heat goes up the chimney and you still may be only 25% efficient. If the fire costs you three times as much as the central heating for the same heat then you will still make savings as long as the room is less than a third of the house, more or less.  From my experiments  - Energy savings from not heating the spare room - heat leaks from one room to another through the walls so you will inevitably heat some of the rest of the house whether you like it or not. In fact this is a good thing as it helps protect against condensation problems in the other rooms. Finally, if your fire does not have a thermostat you may find you end up heating the room more than you would have done.

In conclusion then, we probably don't need to heat our living rooms to 21°C unless we are uncomfortable at lower temperatures, or if we have restricted movement or are otherwise vulnerable. On the other hand, it does make sense to have a 'warming room' in very cold weather, in case we need to warm up quickly. It can be economic to run the central heating at a low level and keep just one room warm using a separate heating device with a thermostat. However the savings this brings depends on the relative fuel cost, heating efficiency of the device, and the size of the room relative to the house.

For more advice on optimising your central heating system read 'Managing your home heating' from Transition Cambridge Energy Group.

Added 23/10/2014
The government has changed its advice - the Cold Weather Plan for England 2014 now recommends that 18C is sufficient, or even less if you are healthy and active and wear suitable clothes.

[1] Cold weather plan for England 2013 (www.gov.uk) Oct 25 2013
[2] Thermostats and controls (Energy Savings  Trust)
[3] HSE Temperature Frequently Asked Questions (www.hse.gov.uk)

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