The Mollier diagram (h s chart) of enthalpy of moist air versus its water vapor content ( h x diagram) is equivalent to the Psychrometrics Chart commonly used in the USA and Britain.

This, as it turns out, is not only good for your aging parents to keep them close to the family it imparts about four to six years of extra life expectancy research shows it's also good for the children of those families, who have lower rates of mortality and lower rates of disease.