If we have a dewpoint of 40 degrees, any surface in the home that reaches this temperature will have liquid water on it. To prevent this condensation, we can either raise the surface temperature or lower the relative humidity. The following graph helps explain dewpoint and relative humidity data as they apply to our homes. If we start to lower the temperature, our RH goes up, and at about 62 degrees we would start to see condensation, let's say on our windows. We could then raise the temperature or lower the relative humidity to get the window surfaces above the dewpoint, and eliminate the window condensation.
Pressure moves from areas of high pressure to areas of low pressure.
Pressure and holes are one of the biggest concerns in residential construction, and they are tied into much of what we need to understand about how our homes function. In order for pressures to influence how a house performs, there needs to be either an intentional or unintentional hole associated with pressure. If you feel cold air entering your house, this is a result of both a hole and pressure. If you take either of these away, the hole or the pressure, the air will not move. An important point to remember is that cold air entering your home may be replacing warm air leaving your home.