We have a utility room that sits off the kitchen on one side (shared wall), and has access into the garage on an adjacent side (single skinned wall and basic fire rated door to garage). The utility room also has two outside walls, one with a window and UPVC door, and the other a double skinned wall (I assume insulated like the rest of the house). It is about 8' x 8' in size.
The utility room itself is a single-storey Construction, with a tiled roof that is shared with the main garage, but the dividing wall between the utility room in the garage extends up into the roof space. The utility room has around 120 mm of loft installation in the roof space (the garage has none, but there is the dividing wall present).
Despite having the radiator, the room itself seems to be cold in winter (and there is a draft coming in to the kitchen unless the door is kept shut), and in the summer the room seems to get fairly warm if the door is shut (it is south facing, as is the kitchen).
I'm wondering where the most significant heat losses will be from, and whether it is worth adding some insulation to the single skin wall between garage and the utility room (it would have to be on the garage side) or whether that's a waste of effort given losses from the door anyway.
Thanks for any tips you can offer!