I have begun working on a net zero energy project and it has become apparent that the exterior envelope becomes increasing important. This project is shooting for an exterior wall with a R-40. This is through the main wall assembly, not an average R of the wall. Both of these will be discussed further.
In order to super insulate the exterior wall in Minnesota’s climate, it is mandatory that the dew point inside the exterior wall assembly be understood. In order to do this an understanding of the Psychrometric Chart and an ability to chart the temperature change through the various components of the wall assembly is important. This could be done with a computer program, WUFI, the Germany program is an example, but doing some calculations by hand and plotting dew point on a Psychrometric Chart is a valuable tool and gives the users a good understanding of both the dew point and the science behind wall assembly failures and successes. Above is a copy of the Pschrometric Chart, in the following posts it’s use will be explained.