I am about to start a project to install underfloor heating on the ground floor of a 1930's built UK house. The downstairs is a suspended wooden joist (50x100mm) construction with about half a metre underneath. The intention is to insulate between the joists with 75mm of Kingspan TF70 insulation, chipboard floor on top replacing the existing floorboards.

The chipboard is pre-routed to take the underfloor heating pipe. My question is regarding the damp proof membrane, the underfloor heating system providers notes suggest a membrane should go above the chipboard and pipework and underneath the top surface (in my case engineered bamboo). Kingspan's installation guide does not make mention of any vapour control for this method of installation in the install guide (page 43) and I've had other people suggest that I should put a vapour barrier across the top of the joists before laying the chipboard.

My thoughts are to either:

  1. Simply use aluminium foil tape to cover any gaps between insulation and joists
  2. Go with UFH board manufacturers recommendations, however, this would seem to create a slight thermal barrier between the UFH pipes and the top floor surface and I'm unsure how I then seal the edges which would be under skirting board.

Would appreciate any advise!

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