So the “garage” slash rear storage area is heated?
Not necessarily actively heated...
The answers to all the issues of cold weather capabilities are dependent on the specific truck. GXV is not building a standard design as you would get from EarthCruiser (for instance) where each truck is designed with specific cold weather capabilities. While there are general designs for the systems, each GXV truck can have variations which will effect cold weather capabilities.
I am most familiar with the Kenworth Patagonias so I can discuss some of the differences.
All the trucks I have seen have a cassette toilet or some other type of self contained toilet in the heated area of the cabin so that is not an issue. The grey tank is generally located in a lower outside compartment so it does need to be considered in the cold weather capabilities. The fresh water tank is located under the bed and while this is not an actively heated area it should not get cold enough to freeze even at the floor level which would be the place where the greatest heat loss would occur.
The rear storage area can have active heating or just passive heating through the walls from the actively heated cabin area.
There are two standard heating systems, the Webasto Dual Top (hot air and water heating) and the Webasto Thermo 90 (hydronic heating using radiators and a heat exchanger for hot water heating).
Our truck, for instance, has a Webasto Dual Top located under a front bench seat in the cabin area with two hot air outlets along the baseboard on the driver side of the floor. Ours has no active heating in the rear storage which does limit our cold weather capability compared to trucks with active heating in that area. Another truck has the Webasto Dual Top located in the rear storage area with ducts up to the cabin for cold air input and hot air return. In this design, the rear storage area gets active heating from the Dual Top itself and the hot air ducts exiting the Dual Top. The ducts can be insulated to control the amount of heat given off in the rear storage area.
The Webasto Thermo 90 system allows a lot more options on heating various areas using radiators and you will see radiators in the bath area to heat it and to use to dry clothes/towels. Our truck has no Dual Top heat outlets in the bath so we need to keep the door open if we want to keep it warm sometimes. The Thermo 90 is usually located in a lower outside compartment along with the grey tank in the compartment (heat from the Thermo 90 keeps the grey tank from freezing, our truck with the Dual Top has an electric heating pad under the grey tank to prevent freezing).
So, as part of the design process it would be necessary to understand what type of cold weather capability you desire and make sure that the truck is designed to meet that need. If you want extreme cold capability then you would probably want active heating in any area where there is the possibility of freezing the water lines or lithium batteries at the temperatures you are designing for.
So, lithium batteries and water lines are the two items that are going to be effected by cold temperatures.
- The Lithium batteries are generally located in the rear storage area on the wall that separates the rear storage from the fresh water tank under the bed. The batteries, inverter, and solar controller are usually next to each other along with lots of other Mastervolt stuff. Assuming you are living in the truck, the heat given off by the inverter, solar controller, and the lithium cells will keep the batteries above freezing since the wall they are mounted on does get heated somewhat from the cabin heat. I have seen batteries mounted on the side wall which could result in more heat loss through the wall though. I think the issue of lithium battery temperature is probably not something that is a concern even for rear storage areas that are not actively heated but at extreme cold temps it may be something to address.
- The issue of water lines freezing is something that needs to be addressed since they generally run along the floor in the cabin and back to the water tank under the bed and to the water pump which is located in the rear storage area along with a water filter. Without active heating in the area where the water lines run along the floor outside the active heating in the cabin you will have a lower temperature limit set by the loss of heat through the floor resulting in a frozen water line. Again, something to address as part of the design process with GXV based on your cold weather requirements.
These trucks can be made as cold proof as you want but you do need to address it as part of the design process.