Stuff in loft going mouldy?

Sammysmiths

Well-known member
We’ve been in the house 4 years and everything has been ok up to now. Since Christmas I’ve noticed mould and mildew on suitcases and other stuff. Standard roof tile construction with black membrane behind.
I’m not sure if we have leaks or if it’s due to us leaving the heating off due to the cost of living.
Any ideas?
 
We’ve been in the house 4 years and everything has been ok up to now. Since Christmas I’ve noticed mould and mildew on suitcases and other stuff. Standard roof tile construction with black membrane behind.
I’m not sure if we have leaks or if it’s due to us leaving the heating off due to the cost of living.
Any ideas?

We had the same issue just before Christmas. Like Norfolkred mentioned, its because we used the heating less, and with it being winter haven't had the windows open, so dampness sets in. I put a 12L dehumidifier up there and its sorted it (y) . Its amazing how much water they can takeout of the air in just a few hours. Also worth using it whenever someone uses the shower or uses the oven hobs to boil food etc. If you don't have good ventilation or don't use the heating enough in winter the dampness builds up causing the mold.
 
I'd bet money on your loft having black bitumen felt which doesn't breathe

If you have spotlights in bathroom ceilings these allow moisture up

Warm air gets up through loft hatch if not insulated and sealed with draft foam, light fittings and when you've had hatch open for devs etc and moisture condenses on felt and drips down

Solutions - google lap vents and install approx 20 at various points between the felt joins, this allows air to flow in and out the loft stopping you having warm air up there

Get a couple of ventilation tiles fitted

Put "loft lids" on top of spotlights and seal with sealant

It'll go away
 
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Hopefully this is what TFG had in mind in his post

Yep thats them

easy to install, just push them in and put the clips over the lip.

Outrageous cost for what they are - half the country has the same problem atm so theyve gone from about £1 each when I ordered mine in October to £2-3 each in some places now but think coming down in price a bit now. Check amazon for prices

these are loft lids:

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you put sealent along the bottom, put the cable through the hole and then seal it to the plasterboard and then put insulation over the top. stops damp air coming up from bedrooms, laundry drying, showers etc.

theyre £4-5 each unfortunately but they do the job.
 
Likewise if you get condensation on your windows in the mornings through breathing, laundry, showering etc - google PIV system, they're about £250 (+ fitting) and will circulate air from your loft around your house which will stop the condensation. Dont get a heater version as they cost about £3 a day to run lol
 
If you want to be a cheapskate you can buy a few lengths of pipe lagging and cut it into 1 inch pucks and shove that between the felt but i would just get the lap vents personally
 
A lot pf people I know who have had the heating off are buying dehumidifiers due to the build up off mold etc.
We've been using one for years with and without the heating, it's a god send and cheap to run.

As for the OP it sounds like a lack of ventilation.
 
Vents might not do anything (in winter), as uk air is humid anyway, just swapping humid air for humid air.

The reason you might have more damp/ mold with heating off is that it will be colder in loft, and now could be below the dew point (this doesn’t happen in summer). The air is no more moist, it’s just that the moisture can now be realised(released).

If that’s the case, only way is to raise temp above dew point (put heating on in house more), indirectly warming loft. Or you can put a dehumidifier in loft, but if doing that, try and seal the loft, so you’re not trying to dehumidify the world.
 
Vents might not do anything (in winter), as uk air is humid anyway, just swapping humid air for humid air.

The reason you might have more damp/ mold with heating off is that it will be colder in loft, and now could be below the dew point (this doesn’t happen in summer). The air is no more moist, it’s just that the moisture can now be realised(released).

If that’s the case, only way is to raise temp above dew point (put heating on in house more), indirectly warming loft. Or you can put a dehumidifier in loft, but if doing that, try and seal the loft, so you’re not trying to dehumidify the world.
vents will definitely help in winter because without them, despite humidity, warm air from the house has nowhere to circulate to in the outside world in most houses that don't have ventilation tiles. The air that circulates may be humid but it is still circulating, exact same principle as positive input ventilation systems stopping condensation on windows in houses.


Our heating has hardly been on and they solved the problem for us this year, installed in winter, after having the issue last year.

Dehumidifiers aren't that cheap to run imo esp compared to PIV systems. Most are 300-400w which adds up with regular use
 
vents will definitely help in winter because without them, despite humidity, warm air from the house has nowhere to circulate to in the outside world in most houses that don't have ventilation tiles. The air that circulates may be humid but it is still circulating, exact same principle as positive input ventilation systems stopping condensation on windows in houses.


Our heating has hardly been on and they solved the problem for us this year, installed in winter, after having the issue last year.

Dehumidifiers aren't that cheap to run imo esp compared to PIV systems. Most are 300-400w which adds up with regular use

You’re possibly right for your instance but may not be for others, same as me etc.

Depends how leaky the house is for heat, into the loft, and how leaky that is to the outside world. This dictates temp, and temp curve meets dew point, for any given humidity. It’s effectively an equitation, with a few different variables and switching one variable likely won’t fix the issue, if there are other issues also.

Adding a vent might decrease humidity, but only if the air coming in replacing it is less humid, which isn’t easy to do when humidity outside is 80-90%.

Source control is the best way, vent fans to outside in showers/ hobs etc, this is also quite good as you’re often swapping out heat where you don’t need it. In a loft you could be swapping like for like and making it colder, which doesn’t
do anything for humidity, and will make it colder, which will make any humidity more of a problem. Also means your house will cost more to heat up, especially if insulation is crap.

Dehumidifiers are expensive, but running one for half an hour a day, with a humidity cut off at say 70% can be efficient in most cases, certainly not all though. Depends on the house type too etc, and how old it is, how many people in there etc.
 
Had a ridiculous amount of condensation running down the loft insulation weeks ago after a cold spell.
Called my roofer mate who fitted 6 vent tiles , job sorted instantly .
£300 but worth it .
 
Had a ridiculous amount of condensation running down the loft insulation weeks ago after a cold spell.
Called my roofer mate who fitted 6 vent tiles , job sorted instantly .
£300 but worth it .
yep, pretty much any roofer or roofing website, community / DIY forum etc will tell you the same in that you need more ventilation. Doesn't matter that humidity is high outside, it's giving the air that is in the loft somewhere to go.

Most people have a cold rooof system (insulation on top of ceiling) and they rely on ventilation to work. Need to make sure that loft insulation doesn't go right up to the eaves as there should be ventilation points there too, and insulation can block it - same with loft boarding, always want a gap. Ventilation tiles are best but lap vents will do in a pinch and can be DIY fitted.
 
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