>>2776988Your base layer is not meant to keep you warm, it’s to aid in moving water (sweat) away from your skin.
Any insulative properties it has is a byproduct.
GSM primarily has to do with durability, with some advantages and disadvantages depending on it being wool or synthetic.
For example a higher gsm synthetic will be more durable, but it will also have a lower cfm and not ventilate as well, so your sweat will have a harder time moving through the fabric and away from your body.
A higher gsm wool will have the same drawback of a lower csm too, but because unlike synthetic, wool is hydrophilic and works by wicking your sweat away through absorbing it into the fiber, a higher gsm also means it had more capacity to wick away sweat before becoming fully saturated.
Keep in mind that once it’s fully saturated, wool does take longer to dry than synthetics, and a higher gsm wool will take longer to dry than a lower gsm wool if both are fully saturated.
