Insulation of garage ceiling to hopefully warm up the room above

Use cavity wall insulation or Kingspan insulation sheets and then tack plaster board over it. The plasterboard on the walls depending on the construction, can be screwed to timber noggins or use thermo board and mechanically fix with plasterboard adhesive.

Personally I would use a 100mm kingspan insulation board between all joists. Cover the ceiling using a thermo plasterboard, which has a foil backing.

Hello, To insulate a ceiling you can use insulated PIR screwed to the joists topped with loft between. If not the below may help. Depending on how the room above the garage is constructed. If this is joists the best thing you can do is below 1. The Rafters - PIR Insulation between the rafters and to the depth of the rafter. Use a 500g clear vapour barrier over the top then 15mm plasterboard. You can also use a superfoil before the plasterboard 2. The Joists - 200mm loft roll between the joists. If being used in a loft situation the also do 200mm loft roll across the joists. PIR is more expensive the glass wool but offers better thermal properties. Kingspan is better than PIR but again more expensive. Budget would depend on what you use. Also the build up of the room would make a difference.