Macmikeman,
Very interesting point. Even when fully kiln-dried, timber contains about 6% moisture, not far off ONE AND A HALF PINTS PER CUBIC FOOT in pine! In older houses in summer it might rise to 12%-15%, falling to perhaps 6-10% in the heating months, but in older damper houses it might be as high as 20%, and has to be this high for fungus attacks to proceed. The water is 'locked' into the twisted cellulose fibres of the wood, takes considerable energy to remove, and there is a gradient rising toward the centre. Larger, particularly oak, timbers never dry out fully, and on a big beam, such as in an old church, the core will be as wet as the day the tree was felled, perhaps as high as 50%! So if these pens are very sensitive, they may well detect stray currents in a quite dry-seeming to the touch timber structure with K&T. As an aside, wood also moves dimensionally when moisture content changes, so a woodworker has to allow for it in every object he makes, ( hence panels in doors), an unwanted complication!
Alan
