A few months back we took out our back boiler and put in a stove which I must say has been a great success. Before putting it in I discovered we had a closed loop heating system (oil boiler and back boiler) with no header tank. Anyway the plumber putting in the knew this and told me (as well as others) that it shouldn't be a closed loop and he'd have to put in the header. He did the job and all was fine until I noticed some air in the rads that I had to bleed. He came back a number of times and tried different things to remedy this but nothing worked until he put another pipe into the header tank - I'm not sure for what. Anyway - no air in rads now. However recently I've been in the attic a few times and noticed some floor boards damp, I went looking for a roof problem and found the inside felt damp over a fair big area. I just happened to look at the header and felt it warm and when I put my hand in the water was maybe 30dC - you could wash up in it. Is this normal for the header to be warm and could it be causing condensation and that's what I felt? Is this a problem?