This topic is maybe not the most challenging, but it is very important. According to the Swiss ECO-scarcity method (UBP), the transport of raw materials and cellular glass is responsible for 20 % of the total damage to the environment due to production, transport and installation of the cellular glass. In other words, 20% of the UBP is caused by transport. It is clear that efficient packing becomes very important.
Forty years back, 40mm cellular glass boards were the standard while today 140mm is the most popular thickness. Transporting 40 mm boards horizontally is a risky operation while this seems logic for 140mm boards. As a consequence, the cellular glass world started to transport vertically. The internal trailer height is maximum 3m with 2.45m internal width to be used with exchangeable EUR-pallets or thinner single use versions. A typical trailer has a floor for 33 pallets, which can be double stapled in the case of cellular glass.
In case of vertical stacking, the boards have a width of 450mm (height when stacked) and 600 mm length (half pallet length). Six parcels have than a total height of 2.70m which should become 2, 984m theoretical total height with two EUR-pallets (144mm height) to be installed in trucks with internal height between 2.85 and 3m. This is not possible and for that reason thinner and weaker pallets are used for this application to gain about 10 cm tolerance. However, these pallets cannot be exchanged because they are not designed to carry 1500 kg. In case of horizontal stacking, exchangeable EUR-pallets can be used because height is not critical anymore. Two pallets stacked have to respect a 2.80 m limit to allow loading the trailer. This means that a trailer can be maximally loaded with 79m³ cellular glass.
In case of vertical transport, the pallets have a fixed height with thinner pallets and I assume that slightly more cellular glass can be loaded, improving the UBP-score due to transport with I guess 4%. But using single use pallets instead of exchangeable EUR-pallets is responsible for an increase of 3.5% UBP. On the other hand, a width of 450 mm (vertical transport) instead of 800mm induces more joints after installation and so a decreased thermal resistance. Joints between 0.6 x 0.45m boards are responsible for 5% heat leak , which means that 0.8 x 0.6m boards should leak 3% in the joints.
At the end, vertically stacked or horizontally stacked boards are nearly equivalent if we speak about ecology. The choice depends on the requested dimensions and it looks that larger dimensions (thickness and length) are becoming more popular. Therefore, I guess that horizontal transport with EUR-pallets will be the future on the condition that the EUR-pallets are not covered by hot bitumen on the roof.