Don’t turn it off and freeze your guests, but turn the old thermostat down a few degrees to account for the fact that all those warm bodies will be generating a lot more energy than you by your very lonesome. All the chatting, bustling about, and activity will naturally increase the temperature inside your side and it’s better to lower the temperature now than it is to open a window if it gets too hot!

My recommendation is to knock it down by only a few degrees, at most 4 or 5, so that it’s cool but not cold. You want your guests, who are coming in from the cold, to feel warmer on the inside but not hot. Most heating systems have merely and on or an off setting so the temperature is only important such that it doesn’t kick on the system when you already have a dozen or so bodies heating up your place.