I guess it is different from region to region and for various types of boats. Would a boat with a cored hull act differently than a non-cored hull?
The winter that Sailing Chance spent in New York Harbor was one of the wettest winters on record. During the time they were there, there was rare blizzard that hit, dumping an above average snowfall for NY City.
It also depends on the number of breathing beings on board. I know, from my backpacking days, that having two people in my tent makes a big difference from when it's just me by myself.
Sailing Chance had two adult humans and, I think, one or two large dogs. Three or four large lung breathers on a 42 foot sailboat would likely generate a lot of condensation.
I don't know what you mean when you say "Sailing Chance didn't have a clue", I don't think they imagined the condensation. Apparently it is a problem for many boaters. Your case is very fortunate.
The couple in Sailing Chance experienced real condensation until they insulated with a product called Hypervent ***(See below). Apparently others have the condensation problem, because this product seems to sell.
How many people live on your boat in Toronto and how large is your boat? What is your heat source that keeps you warm enough for shorts and a t-shirt?
How much snow does Toronto usually get in the Winter?
It's curious, the different experiences.
***
HYPERVENT Mat
Hypervent Condensation Prevention Matting
Plain and simple, a differential between the inside and outside temperature can cause condensation. A favorite place for condensation is under mattresses, bunk pads and cushions. Ask any boater and they'll tell you stories of damage caused by condensation.
HyperVent is the most practical solution for the prevention of dampness (condensation) forming beneath boat beds. Before HyperVent, the approach to dealing with dampness and the resulting mold (odor) was to accept the problem as inevitable and to treat the symptoms. The most common treatment was simply drying the bedding above-deck in the sun (if available).
Features:
HyperVent is a special material that consists of a white spun polymer woven into a large open configuration that is bonded to a breathable white fabric layer
This light mesh of polymer does not compress, allowing an open layer of air to form
It is 3/4" thick, allowing plenty of dry air to circulate