Ever since embarking on this project I have been debating what insulation I should install in the van, however now that I have the windows and plan to start installing the over Easter, I have reached the point where I needed to make a decision.
There are various options for for the insulation, ranging from carpet underlay, EVA camping mats, through solid insulation such as Celotex or kingspan, to spray foam. Conventional loft insulation seems to be frowned upon because it can slump and it absorbs moisture, however given the vast amount that I have leftover from doing living room floor I shall probably use it in the sandwich construction of the van floor.
Whilst I would love to use spray foam it is relatively expensive, and there is the problem of getting the van less its windows but with the holes cut to the sprayer. There is the possibility of getting a DIY kit but the smaller kits are just too small to do the van with a 25mm layer of foam and the larger kits are way too much.
Solid insulation foam boards such as Celotex seem to be popular but they are about £17 per 8′ x 4′ sheet and there is the issue of trying to fit a stiff board to the compound curves of the van walls and roof. Camping mats, and carpet underlay all seem to be a bit of a bodge and potentially have an unknown and limited life.
In the end I have opted for one of the more recent additions the insulation market, and aluminium/bubble wrap/aluminium sandwich. Not one of the cheaper end ones that use metallised film, but one with actual aluminium foil. Installed correctly this material is supposed to have a rating equivalent to 50mm of polystyrene sheet and have the additional effect of acting as a vapour barrier.
With the decision made, orders have been placed for a 25m roll of insulation and a can of high temperature resistant contact adhesive.