Attached wins on any single February morning. But for resale the question is which form the street expects — and in half of Calgary the answer is detached.
In post-war and newer suburban communities the front-drive attached garage is the default, and a home with a detached garage or none is the outlier on its street. Outliers negotiate. In the established inner-city communities the expected form is a detached garage off the back lane, and the market prices that as entirely normal — a front-attached garage there can look like the odd one out instead.
So the useful test is not which you prefer. It is what the twenty nearest homes have, and whether this one departs from it.
A detached garage is not a defect in Mount Pleasant. A detached garage in Cranston is a conversation about price.
One thing, and it dominates the rest: at minus thirty you get into the car without going outside. Add car seats, groceries, a dog and an eight-year-old who has lost a mitt, and the value of that is obvious to anyone who has wintered here. Buyers relocating from a milder city routinely dismiss it in October and change their minds in January. It also connects to a mudroom, which is where a Calgary house either works or does not.
Against that: a walk across a snowy yard, a second roof to maintain, and a structure that ages on its own schedule.
Whether the lane is paved and lit, whether the garage sits on proper footings or a floating slab, whether it was permitted, whether the zoning contemplates a suite above it if that is the plan, and — on attached — whether the garage was carved out of living space at some point. Is a garage worth it in Calgary? covers heated, oversized and tandem, and there is a triple garage search if that is the requirement.