I took out the shelves, sealed the outside of the airvents with silicone and started squeezing silicone along the edges of the inside of the cabinet.



I had a bit of a fiddely task trying to close the gap above the middle pillar.

Afternoon:


By this evening I had all the rest of the edges sealed, added a removable step at the front to contain the substrate and will just have to find a way of closing the gap at the back after I've added the heatmats in a few days time.