Insulation

Lets open a can of worms…

I’m pretty lucky in that I have some clever mates. The type who are in charge of building & designing stuff. Big stuff thats expensive and looks pretty. I asked a few of them what would be the best way to insulate. They all came back with different answers, which probably explains why theres no definitive answer out there of how best to insulate a lorry box.

The options seemed to be;

Mineral wool / Lambs wool / Recyclawool / Knittingwool

Pros.

Its cheap! Environmentally friendly if you go for lambs wool or some sort of recycled insulation & breathable. Also makes a great fake beard

Cons.

Probably should use a vapour barrier, potentially could dislodge or sink down the walls during transit, doesn’t add rigidity, needs twice the thickness of closed cell foam according to who you argue with.

TLX silver foil blanket type insulation. Proper stuff not reflectix or bubble wrap foil…

Pros.

Lightweight, won’t shift in transit, vapour barrier, half the thickness of rigid closed cell insulation for the same R value & very high performance if installed correctly & very quick to install

Cons.

Needs a double layer with an air gap between to achieve maximum performance, making it really expensive to use. Doesn’t add rigidity either.

Spray foam!

Pros.

Looks really fun to do if you buy a DIY kit, no air gap or vapour barrier needed, adds rigidity to the structure & very high performance

Cons.

Expensive to have installed, around £40 a square meter. DIY kits are available but we’d have needed to buy 2 kits plus a gun at nearly £700 per kit plus £70 for the gun.

Kingspan / Celotex / Kooltherm etc

Pros.

Good proven performance, no vapour barrier needed if joints taped, adds rigidity & lightweight.

Cons.

Doesn’t bend, needs to be cut to fit tightly and expanding foam needed to fill small gaps. Expensive

So what did we go with?

This lorry is going to get cold in the alps. Metal is a very good conductor so we began to strip out the metal fixtures and fittings inside the box such as the running bars and the load restraint rails. The plywood floor was covered with chequer plate sheets which also had to go. This gave us a chance to repair the plywood floor where necessary and make good. We were constantly sweeping up flour…

There wasn’t that much metalwork inside compared to some of the lorries I’ve seen. But even taking the 4 rails out on each side of the box made the sides of the lorry pretty wobbly. We needed to add rigidity, we also needed to baton it out so we had something to attach the internals to. Our box was made of the older style heavier & more prone to water ingress 17mm sandwich of ply & grp but would certainly give us something to screw into. The rigidity thing took mineral wool and space blankets out of the equation, leaving us with Spray foam & rigid board. I really wanted to use spray foam, as you can see the roof is slightly curved with all sorts of angles in the corners so it would have been perfect, but we simply couldn’t afford it. We went with Celotex in the end, and found a cracking deal from a local builders merchant. Our costs allowed for a 50mm thickness on the walls and ceiling, and we saved a lot of money by using a 75mm slab of high density EPS Polystyrene insulation on the floor.