Loft insulation question

Mark_petty

Hi

I have recently put lots of insulation in the loft. But on the instructions it states "Do not put any under the water tank"
So I didn't put any under the tank. So it has no insulation in that area. The problem I have now is that directly below this is our bathroom. This room is always very very cold and on the ceiling we are starting to get a build up of mould. I wipe it away as much as I can but it still appears.

My question is can I put insulation under the tank? also would this be whats causing the mould?

Many thanks for your help

Mark:beer:

maninthestreet

The risk is that if you put insulation under the water tank, it increases the chance of the tank freezing when it gets very cold. The tank can only have a foot print of a few square feet, so the heat loss from the bathroom shouldn't be very significant. How well ventilated is the bathroom? Does it have an extractor fan?

Mutton_Geoff

Although you shouldn't put any under the tank (it needs escaping heat from the ceiling below to help prevent it freezing), the tank itself should be well lagged with insulation around and on top, so effectively you are building an insulated box where the tank is "part" of the house below.

Sounds like insufficient ventilation rather than a cold ceiling.

Mark_petty

Thanks, ok I understand now. I'm afraid I don't have an extractor fan.

It does sound like a ventilation issue, I will leave the window open for longer.

Thanks again

John_Pierpoint

As already explained, the cold tank in the loft should be wrapped up too it is "inside" the warm part of the house.

However, if you have air from the house leaking into a loft without sufficient ventilation and the water fed into the tank is really cold, it is just possible that condensation is forming on the bottom of the water tank and dripping onto the plaster board.

Get a torch and go and have a look to see if there is any staining on the top of the plaster board.

With the ceiling well insulated, there should not be any mould on the ceiling, except perhaps in the corners, so if the mould forms an outline of the tank above it - I would say that the two are related.

Try to stop warm moist air from the house getting into the roof space (draft strip the hatch, fill any cracks) and make sure you have sufficient ventilation up there in case it does. Beware of mould damage where the rafters slope down into the eves - there should be some air movement into the loft down there; not stuffed tight with insulation.