I've worked on painting the siding of an Old Colonial for several years. The house is large with three sides clapboard and the back yard (west wall) is shingled. The homeowner insisted I caulk the bottom gaps between the siding planks for appearance, and I complied figuring the shingled siding would be sufficient to allow moisture escape. Also, it's certain there is no moisture barrier over the sheathing. Recently, carpenters have replaced some of the siding and mentioned that I shouldn't caulk those gaps (horizontally) under the siding to allow the house to breathe. The homeowners complain the house is too drafty. How should the siding be caulked without a moisture barrier in place? Obviously, they should plan to replace the siding in particular just to get a moisture barrier in place, but they're concerned about the economic worth of such a task. Is there a certain rule of thumb involving this problem?