Keeping the tank’s cool
QI have a stainless steel water tank under my front well deck, accessed by removing furniture and the lower front bulkhead lining. When the air is warm and the water cold, the tank sweats causing mould in the adjacent cupboards. I rotate a dehumidifier and the rooms are well ventilated. What is the best product and method for insulating the tank? Rockwool?
: The tank sweats because it is surrounded by warm damp air. Keeping the warm air away from it, and the accommodation bilge water-free, should minimise this problem – even more if you can fit external vents to get airflow throughout the bilge. Fit a vapour barrier behind the cabin lining whatever else you do.
The easiest method would be to make cardboard templates for each flat surface of the tank to cut polystyrene sheets (say 25mm thick) glued to a dry tank with suitable adhesive. Make either the top sheet or the side sheets oversize so the side of one sheet butts up against the edge of the other. Tape the joints with aluminium tape to complete the vapour barrier. Unless you take the tank out, you will not be able to insulate the bottom.
Don’t just push Rockwool into the cavity because such products can absorb water. But if you can get some large polythene bags, fill them with Rockwool, seal them and pack the void with them.