May 24, 2005, 1:42 PM
Post #9 of 17
Concrete doesn't continually give off moisture. Water has to come from somewhere, and concrete doesn't have an infinite supply.
What concrete does have is a large amount of thermal mass, which means it takes a while to temperature equalize with its environment. So if the concrete is at a fairly low temperature, and the environment around it contains warmer air with a lot of water vapor, that vapor can condense on the concrete. This might be a problem if your climate features a high relative humidity combined with cyclical low temperatures -- if your concrete, which doesn't swing in temperature as fast as the air, is colder than the humid air during part of the day, for instance. It can also be a problem if you have an situation where the temperature inside the home is substantially lower than it is outside of the home, and the air is humid, since water tends to migrate from areas of higher temperature to areas of lower temperature.
The other thing concrete can do, to some extent, is to wick moisture. Concrete is fairly vapor impermeable, but a slab in contact with moist ground, or lower walls in contact with moist ground, if there is no capillary break, can wick moisture from the damp side to the dry side.
Too bad there aren't structural composite material poles. There's a company that, this time next year, will be in business in my hometown that will be making a composite material of recycled plastics and straw that is structural -- it might have a market as vigas in areas with wood boring critters.