-6 F and I.......
 

Shut off my truck, turn on the Espar bunk heater, set the Espar engine heater for 2 hours before I wake up.

Nice and cozy. I wouldn't stand a chance if I left the window curtains or middle curtains open though.

Any colder and we'd have to break out the sleeping bags. 0 to -5 is about the limit, depending on wind direction and speed.

I used to go up to Sydney Montana once a week. I had an Intl road tractor with a 60 series Detroit in it and I had the Espar in it. My truck was not the condo but the 6.5 foot high ceiling and the Espar kept me warm down to about -15f. I did insulate under the mattress with a sheet of styrofoam and a few other places between the cab and the tool box and I also had the insulated sun screens for the windshield. I don't know if thats what they are called but they are the aluminum foil looking panels you put against the windshield in the summer to reflect the sun. Well I found out that they also insulate the windshield in the cold weather. I put them tight against the windshield and it helped a lot.

I'm looking all around for those. They'll help in summer too like you said. I was thinking of permanently gluing one to the window that's way up top. It's useless.

I alos have the Webasto bunk heater and engine pre-heat system. Luckily I have an almost brand new Columbia Mid-Roof with the arctic insulation package and I can stay plenty comfortable down to -20 with the engine off (with the exception of the floor, it will freeze a gallon of water setting in front of the passenger seat). Some of our other trucks that are a couple of years old are equipped with the same systems but they only have three batteries and if they shut the truck off over night they don't have enough juice in the batteries in the morning to get started. I haven't ran into that yet but came darn close a few nights back when I left the TV (and inverter) running half the night. I got a low voltage alarm so I jumped up and hit the starter, I thought I was sunk but if finally fired.

Truck batteries loose efficiency exponetially when it drops below zero and when you have a fridge, TV, bunk heater and engine pre-heater drawing on them it doesn't take long before they won't start the engine. I have been thinking of trying to put a water mat under the batteries that would circulate the pre-heater water through it to warm the batteries at the same time it's warming the engine. Just not sure how to get it durable enough to withstand 300# of batteries bouncing on it going down the road. One of our drivers took 1" styro and glued to the inside of his battery box cover but he said it didn't help one bit because they are still sitting on cold steel. I might try that but also put it under the batteries and just get longer all-thread for the straps. The clearance on the top of the batteries will be close but if I use 1/2" under them and 1/2" on the top it should clear.

You can try some 1/2 or 3/4 plywood under the batteries, has to be better than the steel, I have rubber mudflap material under mine, don't know if it works or not, I change all 4 batteries after every 3rd winter, no matter what.

Insulating the batteries won't help if there's no heat source.

I can run my espar for 3-4 days without killing the batteries. The webasto system must drain a lot more juice. I think the espar is around 2 amps.

If it's real cold, 0 or below I have trouble starting after running the Espar, but I also only have 3 batteries and I have had intermittent problems with them starting the truck period. That's why I am considering the yellow top Optima's and going to 4.

Don't get the optimas. They actually don't have a lot of stored energy.

Look into the Firefly oasis. They're about $350 a pop, but have over 50% more stored energy then the optimas.

Also look at your alternator. Go with a delco remy 35SI or 36SI. Much better voltage control, and really put out the amps when you need it even at idle.

One thing that has helped me is charging the batteries when they're warm inside my truck bay.

FYI: Optimas are not necessarily a great cold weather battery. They tend to discharge quicker from cold weather.

According to Webasto's specs they draw exactly the same as the Espar. In fact there's one of each in the parts room at the terminal and other than the stickers on them I couldn't tell any difference. They even interchange them with the controls on the trucks. One of the Macks has Espar controls in it and Webasto units.

As for insulating the batteries, they develope a little heat on thier own when discharging, not nearly as much as when charging but if I can keep the little bit they are making from being sucked out instantly that may help.