Our boiler is almost outside - its in the old coal house which is quite exposed to the elements as it sticks out from the house and has its own uninsulated tile roof - the boiler was positioned there when we moved in - the only additional protection as far as I can see is that all the water pipes going to and from the boiler are lagged in tubular foam. I think the boiler (halsted combi - Electronic start - no pilot to blow out) is around
10-12 years old and have had no problem with it so far - however some of the components on the circuit board are rusty, but the appear to still work okay - I guess this may be due to condensation forming on the boards due to the large difference in temperatures it will have to cope with in winter when its switched on.Jon