With regard to insulation, the basic principle is that some materials resist passage of heat or reflect radiant heat. Metal is a very good conductor of heat therefore a poor insulant. Also our vans are quite draughty and let lots of cold air in through door gaps, fridge vents etc.
The best type of insulation to use is debateable and depends on the application.
For insulating the body of the van there are 3 choices – foil, wool or rigid boards.
The shiny foil stuff works by reflecting/ not emitting radiant energy. I'm not sure how much heat radiates at ambient temperatures and I am a bit dubious about the benefits.
It should always work best when next to an empty cavity provided that the air in that cavity is kept still. So if using it make sure at least one shiny surface is facing a clear cavity of 20mm+; i.e. don't install it and then cover it with wool type insulation or panels.
Air is a poor conductor of heat (if kept still) and therefore a good insulant. Mineral Wool type insulation (like the stuff in your loft) works by keeping air still. The thicker it is the better the insulation.
If there are gaps in the insulation it won’t work properly, so for insulating awkwardly shaped areas Mineral Wool insulation would be best in my view as it is cheap, easy to cut and fit around odd shapes.
It's also non-combustible and gives sound deadening benefits. Look under the engine cover for an example.
Can be a bit dusty and itchy though (more so with rock wool than glass wool I’d say) so wear some gloves when fitting, seal it in and try not to get it all over your internal panels, carpets, bed etc.
It would be best to choose mineral wool with a water repellant additive like the stuff they use for insulating brick walls (Google 'DriTherm') as when/ if moisture forms somewhere it shouldn’t get wet through which would also spoil the insulation value.
The lower the thermal conductivity, the better the insulation value for a given thickness.
There are rigid board type insulations which have a very low thermal conductivity but these are hard to shape and fit inside panels. Gaps and holes will mean that the insulation is a waste of time, effort and money. They might be good for insulating the floor of the van though where you could use a thin insulation in one complete layer. (Google ‘Celotex’ or 'Tile Backer' or 'Underfloor Heating Insulation')
For heating and ventilation systems, insulation formed into circular sections, flat sheets or bespoke covers could be the way to go.
Mineral wool can also be bought in the form of pipe sections from an insulation specialist, (Google 'SIG Insulation' or 'Encon') which could be useful for insulating pipes and ductwork.
A better choice might be foam stuff in sheets or pipe sections (Google 'Armacell') for this as it is flexible but a bit pricey I think.
For heat exchangers etc. there are companies around who make bespoke valve covers for industrial purposes. These are generally full of insulation and come with lace up ties or velcro meaning they can be fitted and removed for maintenence etc. when needed. (Google 'valve covers' or 'thermal covers'). If given an example of the size and shape I reckon they could easily and reasonably cheaply knock up a bespoke cover.
As for moisture and condensation, warm air carries a lot of moisture but it drops that moisture when it cools sufficiently or hits a cold surface (the 'dew point') and because you are insulating the external surface of the van this will be kept colder than before. Breathing and LPG heating systems produce a lot of water vapour.
The rule is that there needs to be a vapour control layer to prevent moisture ingress as much as possible and somewhere for moisture to escape when it inevitably finds a way in.
The VCL must be on the warm side of the insulation.
That will mean without a VCL on the warm side of the insulation
a lot of moisture will be deposited on the inside of the external panels potentially leading to corrosion. Anyone looked behind their fridge?
Even with a VCL some moisture will still form I reckon because there are loads of holes in panels where moisture laden air can get in and loads of metal passing through the insulation creating cold spots.
It would be wise to ensure all drain holes are unblocked, there is no bare metal visible and preferably a good coating of waxoyl/ dinitrol type stuff for protection.
Hope that helps someone
