Horace Bénédict de Saussure (1740 – 1799) was a Swiss scientist who spent time in the Alps thinking they were the key to the “true” theory of the earth.
He discovered that human hair could be used to make an instrument to measure the amount of moisture in the air. His “hair hygrometer” helped him conduct his research in the Alps although one unnamed and highly dubious source said he spent time in the iconic mountain range to hone his yodeling skills. Using the expansion of a hygroscopic (water retaining) material like hair is just one way to measure the amount of water vapor in the atmosphere. Other methods use the “wet bulb/dry bulb” system using two thermometers to compare the drop in temperature measured by the wet bulb that cools from the evaporation process. It took until 1902 for Willis Carrier to discover the link between humidity control and a successful air conditioning system. Anyone who has experienced a bad hair day or suffers from dry skin can attest to the importance of an HVAC system that can keep the relative humidity at proper levels for comfort and health. Controlling relative humidity is challenging because it is constantly changing and varies with the temperature. Air that is too dry will draw in moisture from the surroundings and this is the reason people suffer from cracked skin and even nosebleeds. Air that is too humid will put the homeowner at risk from mold and even water damage if the temperature drops and that water condenses on any surface. Your local HVAC service company can advise the best way to control the humidity in your house, but you may need to travel to Switzerland to take yodeling lessons.