There is nothing remotely complicated about this.
Heat moves from a hotter object to a colder one (e.g. from your living room into your garden).
The amount of heat lost is directly proportional to (1) temperature difference and (2) time.
So the longer you heat it, and the higher the temperature, the more heat (energy) will get out, and the more fuel (energy) you will put in, and the more money you will spend.
The amount of insulation you have, and the technology of your building construction, does not change any of that.
If you want to ask an entirely different question, like "what will make my house feel more comfortable" or "how quickly will my house warm up and cool down" or "what temperature should I heat my house" or "should I insulate my home" then there are lots of other things you can discuss. But they will not change the answer to your original question.
As Scotty used to say "Ye cannae change the laws o' physics"
http://en.wikipedia.org/wiki/Thermodynamics
Heat moves from a hotter object to a colder one (e.g. from your living room into your garden).
The amount of heat lost is directly proportional to (1) temperature difference and (2) time.
So the longer you heat it, and the higher the temperature, the more heat (energy) will get out, and the more fuel (energy) you will put in, and the more money you will spend.
The amount of insulation you have, and the technology of your building construction, does not change any of that.
If you want to ask an entirely different question, like "what will make my house feel more comfortable" or "how quickly will my house warm up and cool down" or "what temperature should I heat my house" or "should I insulate my home" then there are lots of other things you can discuss. But they will not change the answer to your original question.
As Scotty used to say "Ye cannae change the laws o' physics"
http://en.wikipedia.org/wiki/Thermodynamics