Insulatin Toilet Cistern

[richmidd1981]

Hi All
i am aware that what i am suggesting is almost certainly a stupid idea but i wanted to get some advice. The toilet cistern in the bathroom gets a lot of condensation on it, i know ventilation is the best way to get rid of this. My question is i was wanting to line the inside of the cistern with something to insulate it. Does anyone have any thoughts on the best way to do this?. My idea i had which is very stupid was to cover the inside of the cistern with expandable foam to form a bit of an insulation barrier. is the any reasons why this won't work or shouldn't be done? i am sure the are hundreds and i am an idiot so i am happy to hear these reason.
thanks

 

[TheVictorian]

Use one of those thin foam gym mats, cut it to size and line the cistern with it.

I haven't done it myself but have heard that it works.