When I first moved into my current house the winows didn't shut, there was no ceilings and the wind, rain and snow came through the roof slates and there were no carpets so really drafty floors too.
Inside the house was a solid 5degC colder then outside due to the thermal mass of the house and it having no south facing side.
We also had ice on the inside of the window glass and cooking a hot meal was a pain, had to eat it from the pan to save it going cold too quickly.
I lived by sealing up a room, 5'x6' and leaving an oil radiator running in it. That was the only room I could spend my days and evenings in before sleeping fully clothed with all my wardrobe of clothes over the bed to keep warm.
After five years of that, during building works, I decided it was time to get central heating so I got two of the biggest boilers I could afford to heat the house with.
I think they are economical as they just tick over rather then running all the time. Bags of loft insulation helps too as well as internal wall insulation.
