How much heat do you lose overnight?

[tornadoinsideoutfig]

My house loses quite a bit of heat overnight. Three degrees in twelve hours last night but it has been as much as 6 degrees in previous December and January cold snaps. It has an EPC B rating and my bills are comparatively very low. However I've read that some other people's houses would not drop below 14 degrees. What does your house drop to inside without heating?

We have a digital thermometer in lounge.

It dropped exactly 1c overnight, but it's warmer at the moment.

In winter, we have our heating set to 18c and don't put it on until we get up - if it's really cold outside (say -3 or worse) it can drop as low as 13c - part of that is probably down to the fact there's a cat flap at the end in the extension.

1960s very well insulated house and no heating on this week. Living room at 22 during day. Bedroom overnight 18 and that's with window wide open. (Never ever have had heating on in bedroom)