Simple heat loss calculator for the whole house

Hi there,

I am looking for a simple heat loss calculator for the whole house, for example something that takes into accound the total sq.ft. of slab, windows and doors, and roof and gives a rough estimation of heat loss, to help me size the furnace/boiler. Or, if you have a simple formula that I could use myself, I can enter the surface and the R value of different parts of the house and come with the heat loss for that item, which later will be summed together.
All the heat loss calculators I found are too detailed and they go on a room/floor resolution. Eventually, this will be done by a hvac contractor, but meantime I need to take few basic decisions, so a rough calculation will be enough.

Many thanks,
Beno

I've never used this one, Beno, but you can download a free heatloss calc here: http://www.heatinghelp.com

I used their Whole House Heat Loss Calculations, thanks, Beno.