Introduction To The Tweaks Pages

The tweaks that make up the following pages were made pretty quickly after putting the truck into use as a motorhome. Some tweaks were just part of the finishing-off process; others were required because the original equipment or my original designs did not perform as anticipated. There will undoubtedly be further extended periods of modification as we face new demands and challenges but I'll cover these in a subsequent series of pages named 'Issues and Fixes'


Quite simply, I hadn’t anticipated this issue. Or rather I had, but imagined that our 5 element panels including 40mm of closed cell insulative foam core, and my care in construction to avoid thermal bridges, would have rendered it only a minor irritation at worst. In fairness, the first couple of times that we used the truck we had foul weather for days on end. It was unfeasibly cold and just rained and rained and rained: a good test as it happens.

In a nutshell, in cold and wet conditions, condensation readily formed in the following areas:

  • The habitation box joints around the whole roof perimeter and down each of the four box corners. I worked out that the heavy duty hardwood peripheral frames that were bonded into the panels at their joining points protruded approximately 10-20mm beyond the bonded surface and so allowed a thermal bridge right in the crook of each panel joint.
  • Behind some of the upholstery in cooler areas of the truck. Essentially warm, dry air from the heating system was being prevented from reaching some of the interior walls where they were ‘insulated’ by cushions / mattresses and the air in these areas remained cooler and was therefore incapable of carrying as much moisture before allowing it to settle out as condensation.
  • In the garage area. This was mainly due to no heated air being directly delivered into this area, a lack of exterior ventilation, and the cold bridges formed by the aluminium frames of the large doors.
  • Around the entrance hatch door area. This was a particular problem as the entrance hatch area does not benefit from much of the blown-air interior heat and the aluminium frames of the door and aperture acted as a really efficient thermal bridge conducting the cold outside temperatures to the interior extremely readily.
    • The solutions required were different for each location but all essentially consisted of a combination of preventing thermal bridging where possible and increasing ventilation / warm air flow throughout. For the roof perimeters of the box my solution was to add a layer of 3mm foamboard obtained from The Plastic People that was affixed using Velcro patches and sealed / bonded around its perimeter using Sikaflex. The purpose of the Velcro was to ensure a couple of mm or so of air gap existed between the foamboard and grp panels. This was a time-consuming process as it meant all of the overhead locker doors had to be removed and their runners re-cut to accommodate the extra panel thickness that the foamboard added.

      For the vertical panel joints I used beech strips of the same dimensions as the ubiquitous battens used throughout the truck. These are thick enough to overlap the hardwood peripheral frames of the grp panels and therefore physically prevent moisture-laden air from settling out in the truck’s interior ‘corners’. An added benefit of using beech was that by cutting a suitable groove into the back, the previously visible outline marker lamp cabling could be very neatly covered. They look nice too, carrying on the theme of subtle beech highlights used for the kitchen furniture etc.

      Behind the various pieces of ‘insulative’ upholstery I fashioned spacers to separate the seats / mattresses slightly from the walls and thereby increase air circulation. Depending on the application, I used either foamboard or beech slats. Stopping the upholstery from physically touching the walls in the areas where condensation was an issue did the trick.

      In the garage I skinned the interior faces of the original doors with 3mm thick polypropylene, added a couple of exterior vents through the floor panels to allow more air circulation, and I also added a couple of Truma ‘wall outlets’ to the heater ducting to ensure warm air found its way directly into this area.

      For the rear hatch I custom made a folding polycarbonate cover that works especially well. When deployed it acts as a very good insulator and stops the warm air of the interior from directly meeting the cold air bridged through the hatch door and frame. It is also immensely useful when deployed in its own right when the rear hatch itself is left fully open. It lets in good amounts of light, manages to stop much heat loss, and is a really good insect guard to boot.

      Complementing the war on condensation, the addition of a couple of ‘Fiamma 28’ roof vents has allowed both more light in, and more air to circulate. The vents, even when fully closed, have a ‘passive’ ventilation function which, in combination with the gas-drop vents and new floor vents in the garage ensure a good constant through-put of fresh air. I chose these particularly as they have a really good leading edge profile that will easily deflect vegetation / low wires.

      Altogether, the combination of measures described have almost totally eliminated the condensation produced by two adults, a steaming kettle, wet gear hung in the shower room, and a dog, even in very cold and heavily humid conditions; lots of unexpected work and faffing was required to get to that point though!

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