With such (relatively) meager heat input to an un-insulated, with a significant volume above head level (ie the roof void) cutting down drafts from gaps round the doors and providing any insulation you can will be essential Phil, ultimately it's an energy balance of heat input v heat lost. If you want to minimise the heat input (for cost and effort purposes) and still remain cozy then YOU HAVE TO reduce heat loss, it's simple physics. I suspect your expectations might have been unrealistically high.
Clearly as the property is not yours you are not going to spend hours and hundreds of pounds on it so it seems to me you've got three choices:
1) Spend a little time and money doing what you can to insulate it eg draught excluders round the door gaps and in my case I've lined the up-and-over steel door with a couple of layers of thermal bubble wrap (it's not a great insulator but did make a significant difference). Also, if you've got a concrete floor then line it with old carpet - that makes a huge difference including to the well-being of your feet. I bought some 2" wide rubber strip off Amazon to seal the gaps on the door on the sides and top and I have some wool insulating bags that came in some food boxes that I use to blank off the gap at the bottom. Also the suggestion of an additional fan positioned to suck all that nice warm air down from the roof void and to re-circulate it back to ground level is good.
2) Put more energy in to make up for the high loss rate ie bigger heaters and/or more of them.
3) By a thick coat, a hat and gloves ......
If it really is a short term problem then 2) must be the way to go, just put more heaters and therefore more energy in - the cost will probably be the same as 1) without the effort and you can take the additional heaters with you.
If it's longer term then I would have thought 1) would be the way to go as the running costs will be lower and will, in time, overtake 2).
Option 3) (or staying indoors and watching the telly) probably isn't a solution at all.
Alan
Clearly as the property is not yours you are not going to spend hours and hundreds of pounds on it so it seems to me you've got three choices:
1) Spend a little time and money doing what you can to insulate it eg draught excluders round the door gaps and in my case I've lined the up-and-over steel door with a couple of layers of thermal bubble wrap (it's not a great insulator but did make a significant difference). Also, if you've got a concrete floor then line it with old carpet - that makes a huge difference including to the well-being of your feet. I bought some 2" wide rubber strip off Amazon to seal the gaps on the door on the sides and top and I have some wool insulating bags that came in some food boxes that I use to blank off the gap at the bottom. Also the suggestion of an additional fan positioned to suck all that nice warm air down from the roof void and to re-circulate it back to ground level is good.
2) Put more energy in to make up for the high loss rate ie bigger heaters and/or more of them.
3) By a thick coat, a hat and gloves ......
If it really is a short term problem then 2) must be the way to go, just put more heaters and therefore more energy in - the cost will probably be the same as 1) without the effort and you can take the additional heaters with you.
If it's longer term then I would have thought 1) would be the way to go as the running costs will be lower and will, in time, overtake 2).
Option 3) (or staying indoors and watching the telly) probably isn't a solution at all.
Alan