Hi We have just bought a bungalow that we will be converting to a house/dormer bungalow, the ground floor is joisted and floorboard with a depth underneath of around 600/700mm We cannot decide if we want Wet UFH yet but my wife is concerned the tiles will be cold underfoot if we don't have it...in our old house we just had tiles direct onto concrete floor Whatever route we go down I think we should insulate under the floor while we are doing the project, my question is how would people do this? Rip all the old style floorboards up, screw pieces of 2 x 1 to the joists, slot in kingspan and then replace old floor boards or to me it makes more sense to use the 8 x 2ft new style floorboards? If we did this could we lay tiles direct onto the floorboards or would we need a further tile backer board? In peoples opinion would this help keep some warmth in the tiles so they aren't so cold underfoot Is there any other ways that this could be carried out and would achieve the same outcome? and is this worthwhile doing. All advice/info very much appreciated Many Thanks
Yes it is worth insulating (and sealing) the floor. Best method is the one you suggest. Battens at the bottom of the joists and infill with Kingspan/other PIR board. Gold standard would be batten underneath the joists at 90 degrees and PIR the full depth of the joists, sealed all around with expanding foam. Go with wet UFH with each room controlled by its own thermostat. Other methods: Cut an access hatch in the floor and either: 1. Use battens and PIR boards, albeit cut smaller to fit through your hatch. OR 2. Use a mineral/natural wool between the joists, supported by a membrane tacked to the bottom of the joists. OR 3. Spray foam insulation from underneath. OR 4. Tack membrane to the bottom of the joints, then fill between joists from above with a bead type insulation through holes in the floorboards. Remove the existing floor. Lay membrane over the joists and inserts PIR/wool between the joists. Tack the membrane to the top of the joists. Now all you need to do is ensure the walls and ceilings are just as well insulated! PS A pair of slippers for SWMBO would offer a significant saving over UFH
Wait until you have the UFH defined. Then you use Kingspan/Celotex up to the level where the UFH will sit.