Recycled Glass Insulation

Without a doubt the most frequently asked question by visitors and passersby on their way to the farm shop has been “What is that pile of black stuff in the car park and what’s it for?” Guesses have ranged from pumice stone to coal. While the mysterious pile has excited much interest from all quarters, few have guessed its true form and purpose in the build. Produced in Germany from recycled glass, the foam pebbles are used as an insulation in the foundations of the build. Surprisingly the material is incredibly light – it actually floats on water! – and quite strong with an abrasive texture, very different to the form of glass we all know and recognise.

Just like the extra big bales Peter is using, the underside of the building will be seriously insulated to match. There is a lot of the stuff to go in, 70 cubic meters of it in fact!


P1010146Pile of recycled glass aggregate ready for use in the first farm car park. 

Recycled Glass PebblesClose up of one of the pebbles

Straw bale house bi-foam deliveryIMG_0177

Here the foam glass is being delivered by special lorry, which we bought from Jurgen Baas of Dreieck (Cheltenham) Ltd


IMG_20171011_165707Concrete footings, ready to receive the foam glass pebble insulation

Before we could begin pouring the pebbles there were a few jobs to finish off. First, four  concrete breeze blocks had to be cemented into the center of the foundations. These concrete pylons form the base for the four internal wooden columns that will support the ridge of the roof (see photo above).

The next task was cutting slabs of recycled glass foam to fit beneath the wooden railway sleepers that form part of the external walls foundations. These slabs will stop heat escaping downwards from the underfloor heating through the cement pylons.

IMG_20171011_171326Bricks temporarily prop up the railway sleepers and sole plate. Ready to be replaced by glass foam slabs.

IMG_20171106_150937Peter cutting a slab of the recycled glass foam insulation.

Although taking the weight of half of the walls and roof, the glass foam slabs were extremely easy to cut. A handsaw slid through a block in 3-4 easy motions. Although it was a relief that the material was so easy to work with, it also caused some concern that they would not be strong enough to take all the weight demanded of them. In the end it was decided to trust in the engineers plans and go ahead although extra care was taken not to apply any sharp impacts on the blocks as we found they would break fairly easily if knocked.

IMG_20171106_151126Like a hot knife through butter.

Filing Air Intake Pipe -Photoshop opportunityReady to photoshop….Cutting and filing the ends of the air intake pipe for the fire place. The final pipe to be fitted!

The final step before dumping the recycled glass pebbles was laying a geotex membrane over the ground. This porous non-woven fabric will prevent any mud from rising into the layer of insulating pebbles (thereby reducing their effectiveness).

Ready to RollMembrane ready to roll out. Note the black squares of glass foam insulation sitting atop the concrete pylons on the far wall. 

Which Way Do I Roll ThisYou put your right leg in, you put your right leg out….

Mud Proof MembraneTom putting the finishing touches to the membrane. Note the four cement blocks in the middle and the black glass foam insulation blocks around the outside wall.

Mud Proof Membrane 2Holes had to be cut around the pipes and the cement slabs in the center of the site

Pouring The Recycled Glass PebblesFirst load of recycled glass pebbles in! JCB really saves time on this part.

Spreading the Recycled Glass PebblesTom spreading the glass pebbles. Although very light, we discovered it was quite difficult to shovel due to the friction between the abrasive surfaces of the pebbles 

Spreading the Recycled Glass Pebbles - BreatherSmiles all around! Peter and Tom take a well earned breather to appreciate their work. Solid day of work on site.

Once the membrane was down the pebbles went in very quickly thanks to the JCB. The next step will be to compact the pebbles….and then putting in more pebbles!! The insulation will eventually be filled up to the dotted red line on the concrete footings but as the maximum thickness of pebbles that can be compacted at any one time is 30cm that will have to be done another time. Stay tuned!

To see the next stage and some heavy duty compacting machines click here.

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