I too have a dunsterhouse cabin, 44mm lots and floor and roof insulation. Coldest it’s been this winter is 2, so had my knee warmers on that day 
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Hottest I’ve had it in summer is about 38 but then it has the sun coming into it all afternoon so I just try to do my workouts in the morning if it’s going to be hot.
Bigger space, so I went 12mm OSB. But I have to hit a stud for fixing (or use the plaster board toggle yolks).
Fellow uninsulated timber garage trainer here!
Find having the bike permanently set up is a massive plus. Gather all your gear together with loads of layers on, you’ll soon be warm enough when you get going and start stripping back.
My toes do get cold so I’ve got some merino winter socks and wear them with the Castelli toe covers, keeps my feet lovely and toasty…as mentioned above bring your shoes back and don’t leave them in the garage, go very musty really quickly if not dried out properly.
Also - another vote for the foam interlocking flooring, garage has a concrete floor which was cold, damp and dusty - flooring is a massive step forward, even take my shoes off before I walk in there now!!!
I guess I should stop thinking I have it rough to have to put on a hoodie to go down to my basement to workout 
Damn it’s cold in London today, it’s the wind primarily but I’ve been cold all day.
This is the other problem with a cold garage - it’s only five steps away but the will isn’t there!
I did this too. Halfords have garage floor tiles for cheap when on offer. Easy to cut with a stanley knife and a metal rule.
The only issue I’ve had is they expand in the heat of direct sun through the window. So that’s about 3 days a year…
Just to update on this, Tuesday morning before 7am, snow on the ground and below zero, I still ended up with the cleva fan going during the over and unders!
My usual mantra in winter “If I just get out there I’ll be fine, If I just get out there I’ll be fine…” carry on the chant until you’ve convinced yourself…also do not let a@%e touch sofa with TV on - very hard to recover that situation!
Haha so true. As I headed to the door yesterday evening my son was ahead of me! I had to wait until he’d finished Zwifting 
But I did get out there for about 1.5h, 9:30-11. 
I moved into a place with a single skin brick garage with a reinforced concrete roof that’s about three inches thick.
How do smart turbos cope with humidity and cold? The concrete floor became fairly damp these past few weeks (I plan to seal it in the spring) so I’ve decided to switch to a dumb trainer until March or so.
Mine floods every few months, the Elite Zumo is fine so far.
This