[beeman]

An easy way to insulate the floor would bee fitting a carpet using a thick AP underlay (such as 11m cloud9 columious). That would kill the droughts, make the floor feel/look warmer and more homely. Of cause the carpet you choose would have to bee appropriate for what you plan on doing in the workshop. A carpet such as gala would bee good workshop fodder (easy to clean, low, tight pile etc).