Search and buy a good thermal underwear, plus the high cost of it, in our time, it is not small money just makes carefully and properly care for it.
Wash underwear and can be manually or even in the washing machine but without exceeding a temperature of 30 degrees Celsius. Otherwise, we run the risk of substantially change its quality and appearance. We conclude that the clothes do not tolerate breeches of high degree, it can not be ironed boil, take to dry cleaning.
For washing, you can use a special powder without the addition of a mild bleaching elements, or the soap, because it is quite soft cloth. Better do care thermal underwear by hand without squeezing, and it is not worth much to pull this all may spoil the fabric. Drying is best at room temperature, in any case, not in direct sunlight, as it just burnt out.
If you decide to buy thermal underwear, then know that it is able to serve a long time if properly care for them.