Bodywork and Glass Insulation

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Insulation - General - Covkid

Beat The Winter Freeze And Insulate Your Van

For those like myself that migrated from Beetles and Type 2's, the lack of insulation in T25s (noticeably panel vans) comes as no surprise whatsoever. VW tended to keep things relatively simple, with models ranging from the basic shell to what the company described as 'luxury' - usually meaning an extra bit of trim or padding here and there, but most of them lacked adequate insulation. On aircooled vehicles this could really show itself during the winter and even on a watercooled, a great deal of heat is lost through the body. My thanks to 'Samk' and other for additional images and input.

With many conversions, you may well find the vehicle already has some degree of insulation, but even where insulation has been fitted, its worth having a look to see what materials were used and whether you can improve things. It shouldn't cost much more than £40 - £50 maximum.

You could throw a great deal of money at this including sound-deadening panels (see 'links external' further down this page), but you can do much to retain heat and reduce noise relatively cheaply and without a great deal of work. Firstly, by far the most useful material is the alumninium-faced bubble wrap available in big DIY stores. For one thing it doesn't soak up moisture, and tends to reflect heat back. As an insulation barrier its good stuff, not too thick, reduces noise, and can easily be cut and put under carpets, into door cavities and so forth. If you pick the right week, many shops have two-for-one prices.

Doors & Cab

The front doors are nearly always devoid of any insulation whatsoever - unfortunate since thats the one place you really don't want to be losing heat. You're restricted a little here due to the room needed for the window when its wound down - glass fibre not really an option. However, the Thermal wrap is easily cut to the shape on the door (allowing a couple of inches over at the bottom and sides to wrap round in a loose 'tray' shape. Getting the sheet inside the door requires rolling up the cut sheet, then feeding it through the aperature with the window wound up, unrolling it inside the door (bit of a squeeze) and then taping it in place where suitable. You could if you wished stick sound deadening material or flashband to the outside metal first although the thermal wrap is fairly effective on its own.

Door insulation.jpg

The cab floor (as shown below) should be completely covered in thermal wrap as far up the front bulkhead as you can go, and under the front seats. It will fit nicely under mats or carpets. Harrymann's excellent article (further down this page) details specific measures that can be used to further reduce noise below the seats and its well worth doing if its within your budget and you want to be able to appreciate the subtle nuances of Debussy on your stereo. If you're listening to Lemmy, this may not apply.

Floor insulation.jpg

Here (below), we've covered the area under the front seat (remove one seat to get the shape then cut two layers of thermal wrap - mirroring, as it'll be the same for the other seat base). The wrap should run under the battery and if theres enough room, up the other side. Bear in mind this section is (underneath) wide open to the wind and rain.

Batt insulation.jpg

Sliding Door & Opposite Panel

Again, cut and fit thermal roll. Heres your first opportunity to add glass fibre. I strongly recommend that you either use space blanket (glass fibre encased in a sleeve with both ends taped up), or at least put glass fibre in polythene. If you don't, any moisture within these panels (and T25 windows do appear to leak eventually either through poor design or corroded window rubbers), the fibre will act like a sponge. locking in the moisture and leaving you with panels full of wet fluff. If you encase it, any water should run down past the filling and out through the bottom. You may have to reduce the thickness of the glass fibre depending on the depth of the panel in some areas.

Sliding insulate.jpg

Sliding insulate2.jpg

Rear Panels

Less opportunity for thermal wrap here but I found that glass fibre tucked into carrier bags (not bio-degradable bags) fitted these cavities fairly well.

Rear Hatch

Again, thermal wrap cut to fit then glass fibre in polythene. Always reseal panels with tough polythene to prevent any internal panel moisture warping trim panels.

Door insulation2.jpg

Roof & Floor

My roof was already well insulated (Caravelle) but you may find you have the option to line roof and remaining floor with thermal wrap.


ith 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.

Links - 80-90 Wiki

There are some good links here, in the Camping section of Club 80-90 Wiki Camping interior - rust/insulation

Links - external

Particularly the ubiquitous Bulley-Hewlett link on insulating and heating a camper van Bulley-Hewlett article

Front seat box area

HarryMann: Front seat box/battery box ~ Rust-area and sound/heat insulating

The front seat boxes on the T25, directly above the front spring hanger/turret, consist of a simple sheet steel box, with the flat bottom panels having pressed 'fingers' for stiffening. The box steps down to the battery box behind. They have effectively zero heat insulation, and transmit lots of suspension and road-wheel noise, unless heavily undersealed. The flat bottom is hard to get to and don't think is normally undersealed for this reason, nor the forward or inside faces.

After 15~20 years, these boxes can be showing signs of surface rust underneath, or even be perforated. For some reason the off-side seems worse than nearside on the two I've dealt with, which obviously points at the battery, or its connections and earths possibly being a source. If you're dropping your springs and shockers out, this would be a good time to attack the bottom of the seat tray with a wire brush, partic. checking for seam rust at the far back welded lip (the top of the panel by the handbrake from inside). Though this can be done at any time, access slows you up a bit. Thoroughly dry out once any rust has been uncovered (hot air-gun on 'mild' heat), and treat with your fav rust treatment. This one here has also had a quick spray coat of Chassis Black over the top of a thick brushed coat of Rust Encapsulator.

File:N-s seatbox treated chs.jpg

Next up, once that's all done ~ Stopping that drumming, transmitted wheel noise and keeping your botty warm!

A big difference can be made to this thin panel, by insulating from the outside. I used 12mm foil covered cross-linked ethylene foam (super roll-up camping mat, eBay, about £5 for 2m x 0.6m), cutting it accurately to panel shapes, ensuring it goes right up to the edges. HD spray adhesive onto both surfaces, a couple of thin coats, more if you want to wait for each to tack, then the difficult bit, manoeuvering the insulation panel into place without getting it hung up on the glue in the wrong spot. Having allowed for the thickness and butted them against each other nicely, I finished off with ally foil tape (Screwfix), lapping all the egdes as well as I could. Being a Syncro, a lot of shutz will be flying around up there!

NB. I only did the back (inside most)panel, the top and the front, as the rear step down to the battery box was heavily undersealed without any obvious fractures/cavities. Underseal is a double-edged sword. Where it was not applied to a fully dry area, over seams, bolt heads etc cavities often form, and they are a rust hotspot. If you see it flaking at all, there will be much worse behind as moisture will get in and stay there, and welded/flanged seams particularly, suffer (e.g. in inner wing just in front of the front jacking point).

File:N-s seatbox insulation chs.jpg

Finally, I've started on the inside of the seatbox, using self-adhesive bitumastic sound-deadening. Being a skinflint I've just filled the pressed fingers (cannot find a reasonable cost source of this brilliant stuff). The correct way to use it is to warm it up in the oven, or use a heat-gun (gently), and form it across a large area of a panel, in this case right into the pressed shapes. Ideally, a further sound and heat benefit would be had by also then lining this box out with cross-linked foam, also stopping stored stuff rattling about in there. However, the foil covered one would be better from a fire-hazard point-of-view, though is thicker. Whatever you use, it should either be moisture-proof itself or encapsulated using an impervious barrier such as heavily taped thick polythene (see the Bulley-Hewlett link above).

File:N-s seatbox bitumastic chs.jpg

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