I’m looking for some advice and some second opinions please..... Today my plans have been passed for a new large workshop/garage it’s going to be block work cavity walls with a render external finish, I have all the plans and ideas in my head of how each stage will go but where I’m doubting myself is with regards to insulation? I know and understand that insulation does not make a room warm and that you need a heat source and that the insulation helps keep the heat from that heat source in, I plan on having some good electric oil radiators. Insulation prices atm are ridiculous and I’m not looking to skimp on the quality of this build but also do not want to spend money in the wrong places. In my head I’m thinking don’t bother with the walls and just do 100mm under the concrete floor slab to stop the ground sucking the heat out and making it really cold under foot and then 100mm or 120mm in the roof to bounce the heat back in and stop it rising through and out of the roof. What do you guys think? Any help, advice or opinions are appreciated.