The woolen clothes keep us warm for two reasons: one is that
wool is a bad conductor if heat. Second is that the air
present in their pores is also a bad conductor of heat and
dies not allow the internal heat to go out
Wool insulates and keeps warmth inside because they cannot conduct heat to the outside. Wool also traps air which is also a bad conductor and then helps to also keep all the warmth from your skin inside.
Wool is an excellent insulator. it keeps heat close to the
body by trapping still or dead air within fiber. Wool
fabric also wick moisture away from skin, keeping the
wearer dryer when sweating and cooler when hot.