The British pint is about 20% larger than the American pint since the two systems are not compatible. Almost all other countries have standardized on the metric system, so the size of what may be called a pint varies depending on local custom.
It is usually measured by the depth (in mm) of the water layer that can enter the soil in one hour. An infiltration rate of 15 mm/hour means that a water layer of 15 mm on the soil surface, will take one hour to infiltrate. In dry soil, water infiltrates rapidly.
Thus, for a house with 15 ACH at 50 Pascals (ACH50 = 15), one would predict an average air change rate of (15/20 =) 0.75 ACH. This simple formula yields surprisingly reasonable average infiltration estimates, even though it ignores many details of the infiltration process.any researchers have sought to develop a correlation between a one-time pressurization test and an annual infiltration rate. average infiltration rate (ACH) = ACH50(1) ----- 20. A person conducting pressurization tests on a particular house can collect considerable information about these details.