Cardsfan and I were talking the other night about sheets, flannel ones to be exact. The question came up was this, if flannel is made of cotton and the normal flat sheets we use are made of cotton, why do flannel sheets seem warmer in the winter time and flat sheets seem cooler.
I know that flannel sheets are rougher, thicker, but what is the deal. Cotton is cotton isn’t it? If you put the sheets on a scale there is hardly a difference in weight and both are 100 percent cotton.
It’s similar to why a piece of metal outside in the winter feels colder than a piece of wood. Both are the same temperature, but the piece of metal (normal sheets) have a better thermal coefficient, and thus remove heat from your body a lot better than the wood (flannel.)
So basically, the normal sheets take away your body heat before your body can warm them up to your body temp, and the flannel sheets don’t take it away too fast before you can get them to your temp.
It’s similar to why a piece of metal outside in the winter feels colder than a piece of wood. Both are the same temperature, but the piece of metal (normal sheets) have a better thermal coefficient, and thus remove heat from your body a lot better than the wood (flannel.)
So basically, the normal sheets take away your body heat before your body can warm them up to your body temp, and the flannel sheets don’t take it away too fast before you can get them to your temp.
And as to why flannel has a worse thermal coefficient than normal sheets…I don’t know, but they do seem to be woven differently, and flannel has lots of “fuzzies”, and that might have something to do with it.
Quick one point hijack: If you want some ***really * ** warm sheets, pick up some fleece bedding. I bought some this year and they haven’t left my bed(except to be washed). They are always warm, no body heat necessary. A bit more expensive than flannel, but well worth it. I haven’t even botherd to put my down comforter on yet, and it was below zero last night.
First, fuzz traps air. This is really the significant advantage for down, but fleece probably traps some significant air, too. Non-moving air warms up quickly and insulates well.
Second, fuzz doesn’t contact your skin all at once – both fleece and flannel have lots of tiny fibers on the surface that hold the woven material beneath away from your skin, and if it’s not touching your skin, it can’t withdraw heat from your skin. The rate of heat transfer is what we detect and interpret as 'cold."