Relaying floorboards and insulation

[handbag]

Hi

I am taking up the floorboards in my lounge and dining room and relaying/replacing as necessary.

We are going to sand and varnish the floorboards. I was wondering whether there was an insulating product I could lay across the joists under the floorboards to prevent drafts (and more importantly for the mrs - small animals!)

Or is Gapseal the way to go?

Thanks

John