In the icy weather we’ve been experiencing recently, the space has been very very cold - even with all the heaters on. A lot of the breeze was coming in from the (closed) balcony door.
To keep the heat in, the gaps in the metal door have been stuffed with blue roll. Please do not use the balcony door, unless it is an emergency, the weather gets considerably warmer, or until the door has been properly sealed.