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First Fit Electrics, Insulation and Vapour Barrier

Updated: Mar 15, 2023

First Fit Electrics

After deciding the rough layout of the van and knowing where electric points, lights etc were required, I ran cables at this stage so they would be hidden behind the insulation and ply cladding. I did quite detailed calculations and drawings to work out the power requirements of the various pieces of electrical equipment so that the appropriate rated cables were run. There is advice available online that describe how to do this. It is a good thing to do a spreadsheet to see just how many amps your equipment uses and from this you can estimate your power requirements and leisure battery. If you are going to install solar panels, this can also inform your decision making around how much solar wattage you want. Sounds complicated but if you go step-by-step it's quite easy and there is a lot of information online to help.

I broke the table down into "Circuits" which then helped me to draw up diagrams of for the cable runs. It also provided an estimate for the quantities and sizes of required cable.

So, needless to say, I was a bit pedantic but it gave me the confidence to lay the cabling.


I gave the van a thorough clean, fixed any problems of rust and added the soundproofing and then began to insulate. This is a relatively easy process that involves finding every place where there is an air void and filling it with suitable insulation. I used Celotex board and recycled plastic wool depending on the area that needed insulated. I insulated the floor, the walls, the ceiling and the driver's cabin. For the floor I built a framework of batons to hold the insulation panels and sealed them using aluminium tape. A hardwood ply floor was fitted over the top.

NOTE: The external plastic protectors are attached using clips that protrude to the interior of the van and they aren't sealed. You should seal these from the inside using something like Sikaflex. This will stop moisture getting in from the outside and causing unseen rust.

Cables fed through conduit and floor sealed
Cables fed through conduit and floor sealed

All the cavities in the van that wouldn't take the rigid insulation where filled with insulation wool and on the ceiling I attached the same insulation material that was used on the floor. I also fitted the bed frame to the main structure.

Insulation, soundproofing and vapour seal
Insulation, soundproofing and vapour seal

Once all the insulation was fitted the whole area was vacuum sealed with spray adhesive and a vapour barrier to prevent condensation ensuring there were no opening for possible vapour ingress. This was one of the most important parts of the build. You don't want any vapour to get to the van structure and cause rust.

I should say that, before completing the insulation, I cut the holes in the panels and roof and also fitted the air vents and windows and this will be covered in a separate post.

Next stage: build the garage area


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