Vlog 5: Warm Fuzzies

The time has come to start putting some insulation into the van so in this video I explain my process and thinking and I go off on a bit of a rant about the uselessness of sticking anything on top of foil “insulation” products.

The thing is – and I clearly didn’t explain it that well in the video as I got a handful of angry comments about it on YouTube – foil is not an insulator. Note specifically, I’m talking about foil here, not “foil in bubblewrap” as that’s two different products combined and I’ll come back to that in a minute.

Rather, foil – just foil! – can be used a radiant barrier which is to say it reflects heat that has been transmitted as infra-red light. In order to do this, the foil has to “see” the heat coming towards it and for that to work there has to be an air gap in front of the foil.

So if you line the van with foil but then cover it up with another product such that there’s no air gap, you’ve blocked any infra red light transmission so the foil becomes useless.

Many of the radiant barrier products sold are not simply foil though, that would be too fragile. What you actually buy is bubblewrap lined with foil. The exact same principle applies here in that it must have an air gap in front of the foil side (facing whichever way you wish the heat to be reflected back to, such as inside the van for winter or bouncing heat back out during summer) for the radiant barrier side of it to do any work.

Whilst foil has no insulating properties, I have read (on a British Board of Agrément certificate) that bubblewrap does have a (quite reasonable) lambda value of about 0.033 which puts it on a par with some loft insulation. The trouble is that at a thickness of just 3-5mm, which is typically how these products are sold, that’s so little as to have almost no discernable insulating effect.

Would you accept 5mm of loft insulation to keep you warm in a house?! Heck no, you’d have 100-200mm at least. Similarly, to get any sensible insulation from bubblewrap, you’d need several layers of the stuff, maybe 50mm (10 layers!) at least. What you tend to see in many van builds are 2-3 layers at best but often just the one.

Whilst that will, certainly, have some insulating value because (as just described) bubblewrap does indeed insulate, a couple of layers is a very, very small amount of insulation. These products tend to hide that in small print, along with the need for the foil side to have an air gap.

Thus foil-wrapped bubblewrap has limited usefulness in a van unless a) you leave at least an inch air gap between the foil and whatever the next layer is (whether that’s the ply lining or carpet or whatever) and b) use several layers of the stuff to build up the bubblewrap to a useful thickness.

A lot of van builders swear by bubblewrapped foil and will say “well my van’s very warm, thank you” but when queried, admit they also stuffed conventional loft insulation on top of it, in which case it’s the loft insulation that’s keeping them warm, not the bubblewrap or the foil!

As referenced in my video, Greg Virgoe’s excellent channel is here: www.youtube.com/gregvirgoe which includes two terrific videos about insulation, amongst many others.

If you enjoyed this video and fancy buying me a cuppa, you're very welcome to do so via www.ko-fi.com/davidjohns with many thanks indeed. Or chip in monthly at www.patreon.com/cruisingthecut

Products and tools used in my van build (as an Amazon Associate, I earn from qualifying purchases.)
Ecotree Lithium battery: www.ecotreelithium.co.uk
New heater unit (diesel): https://geni.us/Van_Autoterm
New inverter (Renogy): https://geni.us/Van_RenogyInverter
Sink: https://geni.us/Van_NewSink
Induction hob: https://geni.us/Van_InductionHob
Fridge: https://geni.us/Van_CoolFreezeCDF26
Portable toilet: https://geni.us/Van_Toilet
Mains charger: https://geni.us/Van_MainsCharger
Solar charger: https://geni.us/Van_SolarMPPT
Old heater unit: https://geni.us/Van_PropexHS2000
Old sink / hob: https://geni.us/Van_SinkHob
Old inverter: https://geni.us/Van_Inverter
DeWalt jigsaw: https://geni.us/Van_DeWaltJigsaw
DeWalt drill: https://geni.us/Van_DeWaltDrill
DeWalt mitre saw: https://geni.us/Van_DeWaltMitreSaw
DeWalt circular saw: https://geni.us/Van_DeWaltCircSaw

Keep up to date via Twitter: www.twitter.com/VandemoniumUK
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  1. Dear Mr Jones,
    Firstly, I’d like to thank you for speaking so clearly and the good recording sound, which makes understanding your videos a lot easier to people like me, not English native speakers.
    I have come to your blog from a Google search; then I have discovered your other blog CruisingTheCut. Quite interesting, I have subscribed as well. It is a pity that in Spain (I am located in Madrid) we do not have an inland canals network.
    I am beginning to work in a L1H1 Citroen Jumpy (Dispatch in the UK). Would it be possible for you to answer some questions that arise? My first question would be: Have you noticed -by yourself- a sound improvement by installing the sound-deadening mats?

    • Hi. The sound-deadening mats certainly made a difference to the sound of the van when it was empty; the booming sound was noticeably damped. However, whether that would have happened anyway once the insulation was put in, I do not know. So I cannot say if the mats are worthwhile or not but it was cheap and easy to put them in.

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