Our moisture calculations are a more detailed and accurate assessment of heat and moisture transfer and will eventually replace the Glaser Method (based on ISO 13788), a standard static interstitial moisture calculation.
To date, the Glaser methodology has been widely used to assess the amount of water vapour likely to be generated within the building and the resultant increase in internal vapour pressure above that of external air. The simplified calculation used is based on average monthly temperatures, vapour pressure and steady-state conduction of heat to determine if critical condensation points are reached within one year.
Available within our Wall Systems Apps only, run moisture calculations are based on the EnergyPlus combined heat and moisture transfer finite (HAMT) solution algorithm. Our moisture calculations will eventually be added to Roof Systems in mid-2023 with the intent of replacing the Glaser methodology.
The calculation process is a complex one-dimensional, finite element, heat and moisture transfer model simulating the movement and storage of heat and moisture in surfaces simultaneously from and to both the internal and external environments. As well as simulating the effects of moisture buffering, HAMT is also able to provide temperature and moisture profiles through composite building walls and help to identify surfaces with high surface humidity.
HAMT is similar in most aspects to other established hydrothermal (moisture) simulations as they are based on a common set of assumptions determined by Künzel, H.M. (1995) Simultaneous Heat and Moisture Transport in Building Components. One- and two-dimensional calculations using simple parameters. The main point of difference is the lack of driving rain adopted elsewhere, which the HAMT is currently unable to process. This can have an impact on simulations with highly porous external finishes.