The Room Above
When the room upstairs never comes up to temperature, the floor dividing it from the garage is the reason. That cavity is open to outdoor air on three sides and fibreglass in it achieves very little, because air simply flows around it.
Closed cell in that cavity seals and insulates together. It is among the most noticeable single improvements available to a house, because the change in that room shows up straight away.
The same holds for a floor that overhangs the storey below, or a room built above an open porch.
Attached And Detached Are Different Jobs
Where a garage adjoins the house, the party wall is a fire separation as well as an insulated one, so both the material going on it and the finish covering it matter.
A detached garage or shop is its own building. Walls and roof both want treating, and the roof is where the value sits if there is any intention of heating it.
Overhead doors leak regardless of what you do around them. We will tell you plainly what the door is costing you and whether it deserves attention before or after the insulation.
Heating It Afterwards
Sealed and insulated, a garage becomes a space a small heater can genuinely hold. Before that, heating one is close to heating the yard.
If a workshop, a gym or a woodshop is the plan, say so at quote stage. The depth we specify differs depending on whether you want to work in there in February or simply want the room above to stop being cold.
Covering And Finishing
Foam in a garage that gets used falls under the same covering requirement as anywhere else people spend time, with half inch board the usual answer.
Most people finish a garage anyway, so this is often work already on the list. We will tell you where it applies before you set the budget.