Theres a fair bit of discussion about the pros and cons of insulation so heres my take :-
Theres two types of insulation - thermal and sound.
Thermal :-
Fiber board, glass wool, plastic bubble wrap, polystyrene etc will insulate for heat. In the summer they dont really have much effect at keeping the inside of the van cool since doors, windows, air vents etc make up a huge proportion of the vans surface and coolness can only be maintained by blocking off the windows externally, fitting an air conditioner and then keeping everything shut.
In the winter it helps retain heat if you have heating in the van but its a tiny space to heat with a lot of glass, so the effect is not anything like as much as in say a caravan with its much larger volume and plastic double glazed windows, which make up a far smaller proportion of the vehicle anyway.
Balance this against the truly enormous amount of moisture generated in such a small space as a T2. Either you have some ventilation, thereby negating most of the benefit, or you accept that everything in the van will get damp and there will be lots of condensation. Insulation will trap moisture. Enough said. On top of this I dont go camping in really cold weather anyway.
Sound insulation :-
Very temping this since I do like it quiet :lol:
Sound insulation works mainly by mass. Theres the carpet underlay type which muffles or damps the sound and works best on higher frequencies. Its heavy though and will trap moisture. Then theres the bituminum type sticky pads or roof repair tape, which stops sound and panel vibration by its sheer mass, which means its again heavy. Once applied its also hard to monitor whats going on underneath it in terms of corrosion. For this same reason I would be very cautious about buying an old camper with lots of insulation. If you think filler is bad, just imagine what horrors can be hidden under roofing tape.
Ultimately I like the van to be able to keep up with the traffic so have an aversion to extra weight. Hence - no insulation in my van.
