My house is some 30 years old now. From new, the CH header tank had a plastic cover over it with integral insulated panels hanging down all
4 sides. Apparently these can no longer be obtained. Last summer, the overflow pipe discharged and unfortunately dumped a lot of the water inside the insulated panels, ruining the cover (I have since elongated the overflow pipe so that this cannot happen again. I have wrapped the sides of the tank in a purpose built insulated plastic cover but the only insulated cover I could get was a simple flat one of similar material, which requires its own tank cover beneath it to support it (otherwise it would just fall into the water!). I've constructed a cover out of painted (breathable) plywood, with ledges all the way round to prevent it moving sideways, that fits snugly round the top of the oblong tank. I've permanently fixed two elasticated straps to the top of the cover under which the insulated panel can fit. On checking the panel a while ago, I found the under surface of it saturated with what I assume is condensation. I also seem to remember that the original plastic cover ended up like this as well. I've tried to alleviate the problem by raising the cover about 12 cm all round to allow the ventilated loft air to circulate under it to some extent, but this has made no difference. I'm obviously concerned that if left in that state for any length of time, the plywood cover will eventually be adversely affected, despite being painted.I plan to re-paint the lid in deck paint for added resistance to the condensation and have also considered making one out of 1" polystyrene, but strength may be a problem. Does anyone have any answer to this problem. Can insulated plastic covers similar to my original still be obtained? Also, will the under surface of the cover always be saturated in condensation - presumably particularly in the colder months?