Hi Larry,
When we use the catalytic heater, I start with one roof vent slightly open. As soon as the slightest bit of condensation begins to appear on any window, I open the vent more. In our '67 22' the refrigerator rests directly on the floor and has a door at floor level that I open whenever I want to light the fridge. Under the refrigerator is a hole in the floor with direct access to the outside atmosphere. With the floor door open and the roof vent cracked, we seldom get consdensation, except at the kitchen window. If that occurs, I open the kitchen window just enough to control the condensation.
This sounds like a lot of work, but after the first few times, it became second nature. As for water vapor passing through the inner walls and insulation, I've never verified that it occurs -- and probably never will -- unless the inner skin is removed for some other reason.
As an aside, we learned several things that might interest you. I enjoy comparing and contrasting data while experimenting with one or two of the variables. In each of our Airstreams, the propane heaters are positioned differently which gives each a different impact. My "CAT Comfort Test" included collecting impressions when outside temperatures were between 30-40 degrees. Anything colder than that was irrelevant because we'd be rolling south.
The results of my grossly unscientific and highly subjective test are as follows.
'63 22' Flying Cloud w/3,000 BTU CAT beside/below the refridgerator and facing the sink, plus a propane lamp over the sink. The CAT's heat was not sufficient for comfort, but the propane lamp brought it to a tolerable level. Other parts of the Airstream were warm only because of the small square footage involved. This one feature will be revised as we continue restoring the Flying Cloud.
'67 22' Safari w/6,000 BTU CAT on galley cabinet by door and facing front dinette area. The CAT is very sufficient for comfort. By facing the dinette, the major socializing area is always warm/ often hot. Other parts of the Airstream are always warm, sometimes too warm. The 3,000 BTU setting is used routinely after start up on the 6,000 BTU setting.
'77 31' Excella 500 w/6,000 BTU CAT on galley cabinet opposite the door, facing the side couch. The CAT is sufficient for the comfort of those sitting in the living room area. The other parts of the trailer retain warmth better than any of our Airstreams. Perhaps thermal pane windows contribute to that. Occasionally, a small muffin fan is useful in directing heated air toward the back. The 3,000 BTU setting is used routinely after start up on the 6,000 BTU setting.
'86 32' Excella w/10,000 BTU Ceramic heater on galley cabinet by the door, facing the front couch. The Ceramic Heater is very sufficient for the comfort of those sitting in the living room area. The other parts of the trailer stay warm because of a small muffin fan directing heated air toward the back. The 5,000 BTU setting is used routinely after start up on the 10,000 BTU setting.
Larry, this is more than you asked for, but sometimes a wider perspective helps fill in the gaps,
Terry
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