Insulation from Tetra Paks

Many people think that Tetra Paks cannot be re-cycled, although in fact the Swedish/Swiss company that invented Tetra Pak has spent vast sums across the world to encourage re-cycling of its product. There are in fact scores of recycling collection depots across South Africa. The paper is recovered and recycled by paper mills, while several plants around the world recover the plastic and aluminium for re-use.

(Visit http://www.tetrapak.com/za/Documents/Google Maps/default.html to find a recycling drop-off point in Johannesburg, Midrand, Pretoria, Durban or Cape Town)

I’ve come up with another way of recycling Tetra Paks. I’m collecting aluminium foil-lined milk or juice cartons to use as insulation in my cabin ceiling. The idea is to staple them together in such a way that the foil reflects the heat away from the roof in summer, and back into the cabin during winter. An air gap between the layers will provide an additional barrier to heat transfer.

If you are nearby and would like to help collect the raw material for recycling, or have a use for cheap insulation yourself, here’s how. The most common shape is a rectangular 1 litre milk or juice container, but square 1 litre or 1.5 litre packages are also useful. I’m going to need nearly four hundred cartons!

 

Start by opening up the triangular flaps at each corner. They are only spot-glued and can easily be prised loose.

 

 

 

 

 

When you’ve released all the corner flaps, partially fill the container with water, squeeze the carton to flatten it slightly before closing and shaking. This will allow the rinse-water to flush traces of juice – or milk, especially, from the corners. No need to waste good fresh water – use the rinse-water after washing the dishes. (You DO rinse that nasty washing up liquid off your dishes, I hope!)

 

 

Empty the rinse-water somewhere useful and cut through the top and bottom seams to turn the container into a tube. The narrow strips can be discarded – at least we’re keeping the bulk of the container out of a landfill.

 

 

 

 

 

Now split the tube open by cutting right next to the seam, usually on the back of the pack

 

 

 

 

 

Prize the pouring spout loose with a thumbnail or a BLUNT table-knife and add it to your plastics recycling bin. If the laminate needs further cleaning, wipe with a damp cloth, don’t dunk it in water. Dunking it could make it soggy at the edges, because water seeps surprisingly quickly and deeply between the layers by capillary action. In any case, leave the flattened sheet to dry in the sun.

 

I’ve experimented with the first dozen I brought down in my luggage. (I wonder what a dozen radio-reflective panels looked like on the airport scanner?) Eight 1 litre cartons stapled into four channels happens to fit snugly between two of the roof-beams. The other beams are unevenly spaced, but it would be easy to cut and fold a non standard end channel to fit.

I have no idea what the R Factor of these improvised batts will be, but from a little research on the subject it appears that in winter the greatest value lies reducing heat loss by convection – by trapping the air in the channels, since an air space works best as an insulator if the air is kept static. When I have enough to make another set, the trick will be to devise a way to cut the ends so that each set fits snugly into the next to form a reasonable seal. During summer it won’t matter if the hot air escapes and travels up the slope of the roof to escape from the ridge-cap, but in winter one would not wish to lose that heat. The foil will probably play a greater part during summer, by reflecting solar radiation away.