WOOHOO! Good weather = time to build

[nachoman]

I am curious what builders would say about moisture barriers here in southern Arizona. The Dew Point is the temperature at which water vapor from the atmosphere will condense. In other words, if the dew point equals the air temperature, the relative humidity will be 100%. If a surface is warmer than the dew point, no condensation will occur. In the Phoenix area, the highest the dew point will ever get is about 70 degrees Fahrenheit, and when that happens it is usually for just a few hours following a summer rain storm. Because i never cool my house below 70, I should not have any condensation issues in the summer. In the winter, the dew point inside my house is pretty low, probably around 30-40 degrees at maximum. Inside moisture is probably at a maximum when I am boiling pasta :mrgreen: . That means my attic and wall temperature would have to get down to 30-40 degrees for moisture to condense. That may happen about 5-10 nights per year, but only for a few hours. In my location, I can't see where a vapor barrier on either the inside or outside will be needed.

In Houston, I would imagine the summer dew points can exceed 80 degrees, with the outside air temperature in the 90s. Assuming you air-condition your house to less than the dew point, I would think you want a vapor barrier on the outside.