Start Lagging Now

[skippymoss]

Hi wragster
The foil is only really effective when facing a clear cavity 20mm+ so don't waste your money on double sided stuff if you're planning to bond it to something
The equivalent thermal resistance that is claimed for one sided foil is about the same as about 30mm of a traditional 'DriTherm' from a builders merchant
The double bubble stuff claims to be twice as effective but that's because it's designed to have a cavity on BOTH sides - i.e. you have to find a way to suspend it in the middle of a void
HOWEVER - as soon as the air either side moves about the benefit goes away and it becomes less effective which is what I reckon might happen when driving about
The bubbles themselves hold a bit of air and have an inherent resistance (like all things air filled) - but not that much as they're only a few mm thick
I've just measured the depth of the rear panel in my van (next to the sliding door) and I reckon I could get 65-75mm of DriTherm in there giving more thermal resitance
Still, foil would be better than nothing on surfaces where there was no real alternative
I've seen pics on a bulkhead (where I have brown furry carpet) and can't really argue because it's flexible and can be bonded into shape but if the foil facing rubs off I'd be better of with my brown fuzz I'd bet

[skippymoss]

On the subject of the air cooled heating system, maybe we could make things better.
I've got a WBX so am unfamiliar (not that heating's too great on that either)
Does anyone have an example of one of these jackets from the retired bloke in Manchester?
What's the length and diameter of the heating hose and what's the max clearance around it?

[mm289]

So lets take an example panel.


This is the panel behind the fridge/cooker unit in a 89 Autosleeper. The panel behind the fridge has simply been carpetted, presumably because it is an open space so any insulation would have not stayed in place. The panel further back (inside the rear wing) has had rock wool in place in a 20+mm void.

1. My thinking is, I can't pack out behind the fridge for safety reasons and there is nothing to hold it in place anyway, but am inclined to replace the carpet with the one sided foil. There will be air movement here as there is a vent panel in the van side for the fridge and also a bl**dy great hole in the floor for the gas cylinder vent.
???? Any improvements on foil for here ????

2. For the inner wing panel (which is similar in concept to doors etc,) I am inclined to use a loose/semi solid insulation material. I tend to agree with skippymoss that cutting up celotex and trying to stuff it in is a bit hit and miss as it wont fill the odd shaped voids well. The "old skool" way was rockwool, but as I have seen on my van this retains moisture really well which then sits in the seams and rots them out. Drainage holes don't really exist/work in these panels so your only protection is wax/sealing the inside of panels first.Some thoughts then....
???? Could you use a "real wool" based product like Thermafleece, similar thermal properties I believe but maybe would "breath" better ????
???? In modern cars these panels are sealed with a plastic sheet stuck on with flexible mastic.i am sure this isn't 100% waterproof, but would this significantly reduce the moisture ingress to the panel ????
???? Could a "bubble wrap" type insultaion material (not sure what they are called but plastic air pockets like bubble wrap ) be stuffed in here, the advantages being it is flexible, and will not absorb moisture - not sure how thermally efficient it would be though ????

Discuss

MM

[texasuk]

I stuffed my voids in the panels with wool type insulation wrapped in plastic (bagged, effectively), to hopefully keep them dry while retaining the insulative porperties. I also stuck the foil covered bubble wrap on the panels to begin with.
With the latest thoughts in this thread, have I in fact wasted a bit of time with doing this? I presume some insulation is better than none, but would it have been more effective to have just stuck the foil covered bubbles on the panels and left a void to the inner panel cover?

[wragster]

Hi wragster
The foil is only really effective when facing a clear cavity 20mm+ so don't waste your money on double sided stuff if you're planning to bond it to something
The equivalent thermal resistance that is claimed for one sided foil is about the same as about 30mm of a traditional 'DriTherm' from a builders merchant
The double bubble stuff claims to be twice as effective but that's because it's designed to have a cavity on BOTH sides - i.e. you have to find a way to suspend it in the middle of a void
HOWEVER - as soon as the air either side moves about the benefit goes away and it becomes less effective which is what I reckon might happen when driving about
The bubbles themselves hold a bit of air and have an inherent resistance (like all things air filled) - but not that much as they're only a few mm thick
I've just measured the depth of the rear panel in my van (next to the sliding door) and I reckon I could get 65-75mm of DriTherm in there giving more thermal resitance
Still, foil would be better than nothing on surfaces where there was no real alternative
I've seen pics on a bulkhead (where I have brown furry carpet) and can't really argue because it's flexible and can be bonded into shape but if the foil facing rubs off I'd be better of with my brown fuzz I'd bet

Brill, thanks again skippymoss

[skippymoss]

mm289;
The area behind the fridge - that's a tricky one.
Can't see the point of insulating something that has big holes in - it's like insulating an open window - it just won't work.
The basic idea is to separate the living area from the external environment
Presumably your kitchen design has the fridge boxed in?
But I imagine (if it's like mine) the cold ventilation air is not well contained and can travel all around the backs and underneath the units and into the living space?
Maybe you could extend that unit backwards and seal it against the side of the van?
The fridge sits snugly in the box with the bits needed ventilated hanging out in the cold but separating the cold air from the warm living space?
Maybe the fridge could be sealed in with draughtproofing brushes or rubber tape?
If you can fit some thin insulation around the hidden parts of the box that would be good.
See my rough attempt to illustrate what I have in my mind below;

Fridge box.jpg

Not sure if this makes sense and maybe I'm missing something - would welcome comments
I wonder how they do this on T4s and 5s?

texasuk;
Fitting both insulants wasn't totally neccessary
Having said that it won't do any harm either so might as well leave it where it is
(Bet it won't be the last time we throw a few quid more at our vans than you would have done with hindsight! - I've given up regretting stuff like that now)
If the insulation in bags was thicker than 25-30mm then it will be better than foil alone
If the insulation was thinner than 25-30mm then the foil and a gap would have been better
Hope you've put the polythene vapour control layer back though?

[texasuk]

Insulation was way thicker than 30mm, the bags were absolutely full up and took some stuffing in the voids.

I did exactly as you have drawn above, created a box that sits around the fridge and seals the whole thing in, ready for when I finally get round to fitting vents.

I didn't replace the vapour lock (there wasn't one to begin with), would this make a major difference again?

[skippymoss]

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.

[bmouthboyo]

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.

Coud you explain what would constitute a vapor control layer? Is it that plastic sheet usually behind car front doors? Would you add one to the rear arches, boot, side panels etc?

[boatbuilder]

A thought just occurred to me... What about using breathable roofing felt as a VCL instead of a sheet of plastic?
As far as I know, they are a total air/moisture barrier in one direction, but allow water vapour to go through it in the opposite direction.

[skippymoss]

The roofing felt is designed to go on the outside. Its impervious to liquid water but designed to allow vapour through (think gore Tex). Probably better off with cheap impervious polythene on the inside IMO.

[bmouthboyo]

So it would go Panel / Space bubble insulation / polythene sheet / rock wool in bags ?

[CovKid]

Well yes, but you can't get rockwool in the doors for instance because you need room for the glass to move. I fitted my bubble stuff inside the door (taped to outside metal with ducktape) and more than anything it cuts down the noise. No reason why it couldn't be right behind the door panel too - other than room.

[bmouthboyo]

ah OK, its this VLC im confused about in terms of what and how to apply it lol

[skippymoss]

Hi bmouthboyo.
The vapour control later is just the same as the polythene you see when you pull off a door card.
You can buy thin poly from B&Q or your local builders merchant.
Best held on with spray glue or maybe double sided tape. Ensure no gaps in the seal.