Ever notice how some mistaken ideas just won't die? They take on an air of truth simply by being repeated over and over on the internet (YouTube, etc). Recognizing and disregarding these myths will save you time and money. Here are a few to get started:
- Sheet-foam insulation (Poly-iso, XPS, etc) under a plywood floor will get crushed. NO, and there is a ton of real-world experience and published material specs refuting that notion. Plywood distributes the weight just like snowshoes do. And for the same reason, the floor valleys do NOT have to be filled. XPS is preferred for floors since it does not absorb water; poly-iso for walls and ceiling because it withstands higher temperatures. Hydrophobic batting (Thinsulate, Havelock wool, etc) also works well on walls and ceiling.
- Sound deadening mat (Kilmat, Noico, etc) is needed on surfaces that will also be insulated. NO, it isn't. Sure, it makes a noticeable difference before insulation, but it becomes redundant afterwards. Sound deadening mat reduces noise by dampening sheet-metal vibration. Insulation does the same thing when attached to sheet-metal surfaces.
- Framing out the walls and ceiling with wood is necessary. NO, it isn't. It reduces valuable interior space. Embrace the curves instead. Finish walls and cabinets can be attached directly to the van's ribs and channels. Select finish wall materials flexible enough to conform to the slight wall and ceiling curves.
- Levelling the whole van before beginning the conversion is necessary. NO, unlike a house, the van will not stay level during the conversion process, or afterwards. Instead, use the van’s floor as your reference plane and square everything to it (cabinets, etc). Likewise, suspension alterations to compensate for the van's original rake, i.e., the back being higher than the front, should NOT be undertaken before the conversion is finished, if at all. Added weight from conversion materials and equipment will reduce the rake. Plus, a perfectly level van will only be level on perfectly level camp sites, which are rare.
- A roof rack is the only way to mount solar panels on the roof. NO, panels can also be mounted directly to the roof using low-cost L-feet and VHB tape, a high-strength industrial adhesive designed for applications like this. Thru-roof fasteners are unnecessary with proper surface prep and temperature.
- A Promaster can be transformed into an off-road beast with all the agility of a 4x4. NO, but with realistic expectations, good AT tires, and a cautious, skilful driver, a Promaster is still able to negotiate some pretty rough roads. Also be aware that some forum members have posted having problems with suspension lifts.
- Buying and converting a diesel Promaster is a good idea. NO, it's most likely asking for trouble. The diesel version was only produced in limited numbers from 2014 to 2017 before it was discontinued. Its European engine and transmission have never been used in another North American vehicle before or since. Consequently, parts and knowledgeable mechanics are increasingly hard to find. Search this forum to learn more. The gas Promaster is just the opposite. Its engine and transmission are found in many other North American vehicles, most notably the ubiquitous Chrysler/Dodge minivan.
It's a cross-section of the van with the little yellow square representing a rocker panel on one side. It illustrates that 3 of its 4 sides are under floor level. And yes, there is a lot of thermal bridging through all the metal in the area. Insulating inside the rockers would not interupt that. But insulating over top of the black triangles would help. That said, it's likely a fairly low priority unless you plan on winter camping.
