Loft tanks, condensation?

[m_d_allen]

Hi All,

Had to go up into the loft over Xmas and noticed an awful lot of condensation on the roofing felt lining! This presumably is bad, also patches of white mould on the roofing timbers which were also slightly damp. The roof isnt shot so its not leaking.

I need to get this sorted out and find out whats causing it.

I think one of the causes could be warm damp air from the house rising through our poorly fitted loft hatch so Im thinking of fitting a new air tight UPVC loft hatch.

We have two tanks in the loft, one for DHW and the other as the expansion, neither have proper lids. They are simply covered by poly wrapped fibreglass. I am thinking of replacing both with new tightly fitted lidded tanks. (BTW overpumping is not happening I checked for that)

Add more ventilation to the soffits.

What do you think? I presume replacing the tanks would require some replumbing so could be a bit tricky.

Thanks for any pointers. Matthew

[Man at B&Q]

Have you or previous occupants added more loft insulation without thinking of the consequences? This happened to us, The previous owner added extra insulation such that the loft space became cold enough for condensation to form.

That's exactly what we did.

MBQ

[Andrew Gabriel]

Check for oversized holes where pipework goes into the loft too.

What stops it falling in? (When it does fall in, it can hold the ball valve open.)

If you can get them. If you are making lids, they need to be something that doesn't soften or rot when damp. A sheet of 25mm cellotex/kingspan might do, and double up as the top layer thermal insulation (just a thought, not tried this).

Is there any ventilation and is the roof lined?

Do you have any extractor fans which extract into the loft space without ducting outside (or with broken ducting)?

Otherwise, I think you are looking at the right things.

[The Natural Philosopher]

More to the point, is there a vapour barrier in place..without one you get soggy insulation..

[TheScullster]

"Andrew Gabriel" wrote

snip

I would be careful not to over-insulate the central heating header tank. Keeping this over-warm can lead to fungal growth and nasties taking up residence.

Phil

[adder1969]

But doesn't the loft get hot in the summer? ..thus the header tank also.

My loft wasn't ventilated at all (other than some small holes in the sarking) and the only dampness was under an old plank that was on top of the insulation that was directly above a shower. The ceiling plasterboard is the foiled backed stuff. I guess if there's no ventilation there's not much flow of warm moist air up there?

[<me9]

Unlikely to be a problem, as long as it is sized properly for daily consumption. The extra insulation will keep it cooler in summer, when the problem of legionella would be higher.

[TheScullster]

Not sure I understand the "sized properly for daily consumption" bit. I was referring to the CH header tank not the domestic water storage tank. Both myself and my father-in-law have suffered from this contamination problem and have needed to add Fernox bacteria inhibitor to eradicate.

Phil

[Si]

In message , TheScullster writes

I've also had to add inhibitor to the CH header tank due to fungal growth but I didn't associate it with having insulated the tank.