While I agree that this layout/design is probably better than many barrels in terms of quality of heat, this seems to be an indoor sauna kit. Those generally have minimal insulation and are not designed in a weatherproof way. In your climate I would expect a bad result – we have heard from numerous people in r/sauna who set up an indoor sauna like this in an uninsulated garage (which mitigates the weather issues) but still expressed dissatisfaction with draftiness and difficulty getting to temp in the winter. You could essentially build an insulated and weatherproof structure around it but at that point it seems like you’d end up with a weird sauna and much of the cost savings of a kit would likely be lost. At that point you might as well just do a DIY sauna, which would have the added benefit of being able to use a higher ceiling and bench height.

If you want a propane heated sauna, I am only aware of Scandia’s heaters. It is worth noting that they are not cheap (the small one is $3,600), so it might make sense to do a full cost analysis for a less expensive electric heater with the electrical work you would need versus a Scandia unit. Electric could still be less expensive, particularly if you are willing to do any trenching yourself.

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Is this thing on?