Thermal protective clothing often has a detrimental effect on the wearer’s comfort as a common formula is the heavier the more effective.
Better to start with a fiber like PyroTex^® which by default has an exceptionally high thermal insulation enabling the manufacturers to lower the weight of the garment.
 
Have a look at the video which shows how good the thermal insulation of PyroTex^® really is.

Click here for the video (YouTube)