Building a sauna is a good start. You'll never get really warm to the core anywhere else. Plus afterwards you'll feel like a Jamaican - No worry, be happy.
I think that the winter depression is metabolic origin. Vitamin D is the key element. Eat more fish, meat, nuts, eggs, milk, oils and less bread, sugar, potato and pasta. Specially cut down tomato and red paprika - the red colour stuff dissolves melatonin and you need each drip of that hormone.
The only antidote to mental suffering is physical pain. Unfortunately.
