A special thing happened yesterday morning. The temperature in my living room returned to the same value it was at the start of November. It's been a long winter.
The indoor temperature on 2nd November 2020 was 18°C. The indoor temperature finally got back to 18°C on 12th May 2020. That's a gap of 191 days (or, to put it another way, six months and one week).
To clarify a few things...
» This is the temperature in my living room first thing in the morning.
» First thing in the morning is the coldest time of day in my house.
» First thing in the morning is not affected by any central heating I may have had on.
» I'm not one of those people who leaves the central heating on overnight.
» I don't believe in heating the house while I'm unconscious under a duvet.
To clarify a few more things...
» My thermometer is close to an outside wall quite near a window.
» Yes, obviously I've been keeping a daily record in a spreadsheet.
» Don't say you're surprised.
The indoor temperature started its wintry descent when we had a coldish snap at the start of November. It soon recovered but then began a steady decline to a minimum of 12°C on 7th December. It managed to get back up to 16°C just before Christmas, then slumped into the New Year and spent a full fortnight below 12°C. An erratic recovery kicked in, but a really cold spell in the middle of February dragged morning temperatures down to a wintry low of 10°C. Within a fortnight it was back at 16°C, but only briefly, and there were two more lowpoints at the start of March and April. More recently there's been a long spell hovering around 15°C, until finally this week the temperature shot up and returned to 18°C.
My average first-thing-in-the-morning temperature over the last six months was 14°C. The temperature was below 15°C two-thirds of the time, below 13°C for six weeks and below 12°C for three weeks. Hurrah for central heating and its ability to make the rest of the day less chilly. Hurrah also for living alone, which means I have full control of the radiators.
I'm perfectly comfortable in indoor temperatures of 18°C, I'm not one of those people who needs the thermostat stuck in the twenties. I'm actually OK at 15°C most of the time, which may be a bit more resilient than some of you. I'm not comfortable at 12°C, which is double-jumper weather, and that week of 10°C first thing in the morning wasn't pleasant.
To make any sense of all this, the graph obviously needs a second line.
To clarify a few things...
» The top line is the temperature indoors.
» The bottom line is the temperature outdoors.
To clarify a few more things...
» This is the overnight minimum temperature outdoors.
» I do have an outdoor thermometer so I really should have taken data from that.
» Instead the graph shows the overnight minimum in Hampstead, a few miles away.
As you can see the temperature indoors closely correlates with the temperature outdoors. After a cold night the temperature in my living room is cooler, whereas if it's a mild night the temperature indoors holds up better. A prolonged cold snap drags the temperature down further for longer. There's rarely a lag, it's pretty much immediate.
But the two lines never cross, or even meet, because the brick walls of my flat are good at insulating. In fact the two lines are generally about 10°C apart because that's how good my walls are. The maximum difference was 14°C at the start of November when the walls still held a bit of leftover summer heat. The minimum difference was 4°C earlier this week because it's spring and the building I live in is still warming up.
The first time the outside temperature dipped to freezing overnight (in December) was the first time my inside temperature dropped to 12°C. The freezing fortnight at the start of January was the first time my early morning indoor temperature dipped below 12°C. But it took until the Arctic burst in February for the indoor temperature to reach 10°C thanks to outdoor temperatures below -2°C. At the coldest times the difference between inside and outside is generally twelve degrees.
Now that my central heating has been resolutely switched off for some time, an interesting observation is how stable the daytime temperature in my flat is. For example it was 18°C first thing yesterday morning and then hovered around 18-19°C all day even though the temperature range outdoors was rather wider. The baseline temperature inside a flat or house depends a lot more on the temperature of the building than the temperature of the air outside. A building is slow to warm up in the spring and slow to cool down in the autumn, like the sea, which helps explain why it's taken until May for my indoor temperature to finally match November.
Anyway, it's nice to be back in the half of the year when the temperature indoors is high enough first thing in the morning to be entirely ignorable. But I intend to carry on recording it, if nothing else to observe the effect of outdoors on indoors during the hottest sweatiest bit of the summer. Assuming we get a hot sweaty bit, that is. We've been a long time waiting.
