center of Japanese housing.
Cross section of rush is soonge-like. And straw used for tatami core is just a straw（like a tube）. Both has elasticity and can contains much air. Air is difficult to transfer the heat. In hot summer day, tatami containing much air cut off heat. In cold winter day, tatami mats cut off outer cold air.
Our life is surrounded many toxic substances like Nitrogen oxide or volatile orgonics discharged from tobacco, automobiles and factories. It has been discovered that rush has the nature of air purification. Rush absorbs carbon dioxide and formaldehyde, and purify the air. In other words, rush has the function like natural air cleaner.
It has been discovered that rush has antibacterial properties against pathogens that cause food poisoning. Now rush is being studied for its application to food and medicine.
Modern house are well insulated compared to the past. So, houses have problem about humidity. Humidity can’t go outside. Rush absorbs humidity when air is moist , and when it’s dry they release humidity. In that reason, rush is good for human to keep air condition well through whole season.
Tatami surface is made of rush grasses and tatami core is compression of straw. Tissues of rush and straw contain a lot of air layers, so that tatami mat has sound absorbency. Sound of walking on the tatami mat will be absorbed to tatami. Those functions of tatami mats make us comfortable and relaxed.