Type of insulation to insulate kitchen & bathroom that back onto garage

[David Lindon]

I would like to add some insulation to these walls in the garage as the bathroom is noticably colder as it juts out into the garage. Is something like this the best way to go - https://www.screwfix.com/p/ybs-superquilt-multi-layer-reflective-foil-insulation-5-x-1-5m/80967

 

[Bonni]

If it was mine, I would either dot and dab 50mm insulated plasterboard to the wall, or stud it in 4b2, insulate with 100mm kingspan, and then plasterborad.