12.5kw vs 15kw
I am in the process of designing an outdoor 8x8x8.5 sauna, drawing from Tumpkin's notes as much as possible. For heaters, I'm torn between a Harvia Legend Pro PO12E (12.5kw) or PO15E (15kw).
The Harvia calculator suggests the power of a 11.4kw heater should be sufficient, accounting for a window of 8 square feet.
My concern is that it will be a four seasons sauna and winters in my part of Canada can be below -20C. The build will be well insulated, with the exception of the window (but it seems most on this sub recommend a window despite the R loss).
Will 12.5kw provide enough overhead to cover the temperature drop in winter for a sauna of these dimensions?
The PO15E will be significantly more expensive stone wise, and will take up more space, which is limited given that I am trying to maximize bench space at the proper heights. So I don't consider it a trivial upgrade.
Many thanks in advance. This sub has been invaluable to my planning.