An indoor home sauna is a choice about the room as much as the cabin. The same budget buys three quite different things depending on whether you have a spare bedroom, a basement, a garage bay or a large bathroom, and the constraint that decides it is almost always the electrical rather than the space.
Start from the circuit, not the catalog
Most small infrared cabins run on an ordinary outlet. A traditional heater above the smallest sizes needs a dedicated higher current circuit and a licensed electrician, and in an older house the panel may not have capacity. Find out what your panel can give before you shortlist, because it removes whole categories from the list in one step.
Which room
A basement is the classic site: cool, private, tolerant of a hard floor, usually near the panel. A spare bedroom works for a prefab cabin if the floor and the door allow it. A garage bay suits a larger cabin and takes the heat and moisture out of the living space. A big bathroom is ideal for steam and awkward for a dry cabin.
Prefab cabin or built room
A prefab cabin stands on its own, arrives as panels and can be moved or sold. A built room using a precut lining fits the space exactly, costs less per square foot and is part of the house from then on. If you might move within a few years, the prefab is the better asset; if this is the house, the built room uses the space better.
What an indoor cabin asks of the house
Very little for infrared: a floor, a circuit and a door swing. More for traditional: the circuit, heat clearances, and ventilation so the room the cabin sits in does not get humid. Any built room needs the full wall build-up with a sealed vapour barrier, or you are putting moisture into the house's own structure.
Questions people ask about indoor home sauna
What decides indoor type more than anything?
The electrical. Infrared usually plugs in; a traditional heater needs a dedicated circuit and a licensed electrician, and an older panel may not have capacity.
Is a basement a good place?
Usually the best one: cool, private, near the panel and tolerant of a hard floor. Check for damp before building anything into it.
Prefab or a built room?
Prefab if you might move, since it comes with you. A built room if this is the house, because it fits the space better for less per square foot.