Home DIY

I'm going to put some woodfibre underlay boards down in a small upstairs room. It's a temporary bodge to improve things (gappy draughty floorboards) but hopefully sorted better in the next few years. At the moment is just rugs on floorboards. Two questions:

• if it's done during a hot spell should the boards be butted up rather than leave the customary 2mm gap around? I'd still leave a little gap round the edge of the room.
  
• what tape? It's upstairs, there's no need for moisture or vapour resistance. Everything I read is about using barrier tapes but it seems to defeat the point of using a nice eco no adhesives or resins board to then stick together with plastic tape. Am considering a paper parcel tape seeing as it's just to stop it moving around.