NB12:
Does all that idleing not glaze the bores?
Not if you run it fast, 1000-1200rpm, it keeps it at operating temperature, a diesel engine is actually very good at running at a constant speed, just need to get some heat into them and they’re fine. In modern electronic controlled engines you don’t get so much over fuelling anyway 
It is a PITA idling though, vibration and noise are the main issues, but then again it’s better to listen to your own engine than the ones either side of you 
Mark, the webasto book I was reading has two systems from the same device, the night heater warms the cab and another part heats the engine block.
Not too sure how long the battery would last though ?
Unlike my old Columbia the new Cascadia has curtains that go round the drivers area.
When I was on for Sunbury we all had APU’s fitted. They were okay for keeping the batteries charged but thats about it, and they are prone to breaking down for the slightest little thing. In the 5 months I worked there it broke down 5 times. Fortunetely the truck also had an independent webasto heater as well as it came with that fitted and the APU was put on afterwards by the company. I’ve never had a truck here yet without a heater but plenty of companies still dont use them…I know several who buy top of the range trucks, have all the extras in them, and yet still will not fit a night heater and they have the cheek to tell the drivers not to idle. Well in winter its easily -30’c for a month or so and a lot of trucks here go right down to Florida all the time where in summer +30’c is a cold day so you either idle for the a/c or get heat stroke. That was another good thing about the APU, a nice cool cab without the engine running…when the ■■■■ thing worked!