Loft condensation

[Bryan Williams]

Hi, hoping for a bit of advice on the above..
My daughter son in law and baby have been in her first house now since November and recently noticed the membrane in the loft is glistening with tears of condensation..
It's a 70s 3 bed semi a frame ,her father in law boarded it out with osb right down the middle from end to end lifted on I think 4 by 2.
They've filled that with camping gear and assorted junk..
It wasn't showing any sign off condensation when they had it surveyed but it had been a single girl living there, didn't have the heating on much..they are hammering it a bit ..a lot of cooking showering usual baby care washing..

I had a look today, outside they have the soffit area boxed in front and back, no vents..
They have what looks like original ridge tile vents, narrow slitted type about 2ft in from each end of ridge.

In the loft they have what looks like three different layers of insulation.
A bottom layer of white cotton wool ball looking stuff..a 3 to 4 inch layer of rock wool type stuff and a thicker maybe 8 to 10 inch newer looking layer.

The middle insulation is now under the boarding end to end to the first down struts..behind these struts going out towards the sides the thick insulation stops about ten foot out, then there's the thinner layer of insulation for about 5 to six ft then a couple of ft of the cotton wool stuff..
On the gable end there is a square cut out of the membrane underneath the ridge tile vent..
At the other end there's no hole cut into the membrane
My thoughts for what it's worth is they would need a row of vent holes cut underneath the soffit area boxing with the plastic grills popped in ,front and back.
A hole cut for the ridge vent although they don't look man enough to give good ventilation.. I'm wondering if a couple more modern vents would help

As regards the insulation, where its the newer stuff it looks OK thick enough no gaps , but it's been flattened with the boarded down the middle and I've no idea if it(the new thicker insulation) should go right up to the outer edge just stopping where the soffet vents should be..
The timber all looks in good order
any advice would be appreciated,cheers

 

[Bobtail4x4]

in this cold weather, its normal to get a bit of condensation,
you can reduce it by sealing the loft hatch edges, and introducing cross ventilation to the void,
check also for downlights in bathrooms, they let warm moist air in the loftspace, seal them with a plantpot/bucket over.
even the new breathable felts dont work below zero,

 

[Gareth J]

Standard lofts should be pretty straightforward to sort.

There should be no air from the house that gets up there. If there are leaks around the loft hatch or elsewhere, do your best to seal well. Cavity wall or modern timber trame properties often suffer from electrical, plumbing, door and window perforations in the plasterboard leaking air up through the cavity into the loft. Quite hard to sort that.

Maybe someone has fitted an extractor up there that just vents into the loft space. Or a pipe has come adrift/split.

The cavity should ideally be closed at the top, especially if it's not been filled.

~1 foot of fluffy stuff on the loft floor. Consistent layers.

An airflow path over the insulation, above the walls from soffits. At least some gap between loft fluff and membrane at wall tops.

If you can keep warm, moist house air out of the loft, there should be no issues. You might get brief times where clear nights after warm muggy days condenses a little on the roof but that's transient and if it does ever happen, won't be for long.

 

[Pigeon_Droppings2]

As above, check for anything venting into the loft. Any additional bathrooms or toilets might have a vent pipe with a failed valve maybe.

Air flow is best remedy....if it's 1970 then check the roof vents are secure and not leaking. Any leaks will let in water...that era can have odd vents if the house had hot air heating originally!

 

[Bryan Williams]

in this cold weather, its normal to get a bit of condensation,
you can reduce it by sealing the loft hatch edges, and introducing cross ventilation to the void,
check also for downlights in bathrooms, they let warm moist air in the loftspace, seal them with a plantpot/bucket over.
even the new breathable felts dont work below zero,

There are downlights in the bathroom..but I think they would be underneath the boarded area.

in this cold weather, its normal to get a bit of condensation,
you can reduce it by sealing the loft hatch edges, and introducing cross ventilation to the void,
check also for downlights in bathrooms, they let warm moist air in the loftspace, seal them with a plantpot/bucket over.
even the new breathable felts dont work below zero,

 

[6ply]

We have a cold/ventilated loft space with soffit ventilation all round. But then I noticed we sometimes got condensation on the underside of the roofing felt. At first I mistook this for penetration from the outside. Anyway, the condensation at times was significant enough to drip down and damage a ceiling. I then realised the house humidity was high and bought a dehumidifier. Dramatically lowered humidity in the house and we've not had a problem since.

@Bryan Williams, my advice would be to check humidity in the house. If it is high, ventilate, don't be a skinflint with the heating (especially with a baby around) and consider getting a dehumidifier that is left permanently on. As you have already suggested, soffit ventilation would seem a good idea.

 

[Bobtail4x4]

There are downlights in the bathroom..but I think they would be underneath the boarded area.

the moisture will still get into the loft, can you pull one down, and see if you can add a plantpot / pot noodle pot?

 

[Bryan Williams]

We have a cold/ventilated loft space with soffit ventilation all round. But then I noticed we sometimes got condensation on the underside of the roofing felt. At first I mistook this for penetration from the outside. Anyway, the condensation at times was significant enough to drip down and damage a ceiling. I then realised the house humidity was high and bought a dehumidifier. Dramatically lowered humidity in the house and we've not had a problem since.

@Bryan Williams, my advice would be to check humidity in the house. If it is high, ventilate, don't be a skinflint with the heating (especially with a baby around) and consider getting a dehumidifier that is left permanently on. As you have already suggested, soffit ventilation would seem a good idea.

They do have a decent dehumidifier,but it's just used for drying clothes in a utility room..they're not tight with the heating..I'm going to check all possible gaps and holes.. the loft door is well fitted but just thin board really..

 

[Bryan Williams]

the moisture will still get into the loft, can you pull one down, and see if you can add a plantpot / pot noodle pot?

I'll have a go this weekend.

 

[addjunkie]

They do have a decent dehumidifier,but it's just used for drying clothes in a utility room..they're not tight with the heating..I'm going to check all possible gaps and holes.. the loft door is well fitted but just thin board really..

Does the bathroom have an extra fan that works…..where does it extract too, is the pipe kinked

 

[Bryan Williams]

Does the bathroom have an extra fan that works…..where does it extract too, is the pipe kinked

No, there's no extractor at all in the bathroom..they just open a window

 

[Bryan Williams]

the moisture will still get into the loft, can you pull one down, and see if you can add a plantpot / pot noodle pot?

She's just told me they had them fitted as soon as they moved in apart from one that the fitting was broke and needs fixing..

 

[addjunkie]

No, there's no extractor at all in the bathroom..they just open a window

Fitting one would remove a fair bit of the moisture from the house. Straight out through the wall if needs must, or you can get one that is like a shower light. Buy decent in line Manrose is going up through the loft.

 

[Smallfry]

FWIW my mums house, a semi built 1978 does this. No one lives there, so no heating on, no washing or laundry etc.

It has one airbrick 9 x 3 in the gable end, and soffit vents. The felt is the old sacking soaked in bitumen type, so non breathable.

I guess it is the same as garage and workshops, due to temperature differential at this time of year. Sun warms the loft space during the day, then gets cold, so the moisture forms on the membrane and drips on everything.

I dont know what can be done either However, warm air rises, so may be stuck in the dead air near the ridge, so maybe ridge vents are the answer ?

 

[Bryan Williams]

FWIW my mums house, a semi built 1978 does this. No one lives there, so no heating on, no washing or laundry etc.

It has one airbrick 9 x 3 in the gable end, and soffit vents. The felt is the old sacking soaked in bitumen type, so non breathable.

I guess it is the same as garage and workshops, due to temperature differential at this time of year. Sun warms the loft space during the day, then gets cold, so the moisture forms on the membrane and drips on everything.

I dont know what can be done either However, warm air rises, so may be stuck in the dead air near the ridge, so maybe ridge vents are the answer ?

I'm thinking ridge vents as well and maybe a couple of tile vents..just been looking at Glideveale vents

 

[colnerov]

Does the insulation go right out to the eaves and wedged in stopping air getting in? Is so pull it back a bit or fit some of these -

https://insulation4less.co.uk/products/loft-vent-tray-700mm-x-315mm-x-30mm

 

[Bryan Williams]

No that's one of the things I mentioned..I cannot get right into the eaves yet but looking at it from middle there is some cotton wool type stuff laying thinly between the ceiling joists ,about 2 ft of it up to eaves then for about 5-6 ft coming back there is a layer of rockwool ,about 45 inches thick the n on top of that there a newer thick layer about 8-10 inches thick..
I would have thought the thick top layer would go almost to eaves with a small gap..not stepped down..

So I'm guessing that the whole loft space has the original 70s white cotton wool ball type stuff just between the ceiling joists,then someone's come along and put a thin layer of rock wool everywhere but stopped 2ft from the eaves..then someone's put another thicker layer on top but stopped where the roof pitch is about 2-3 ft high..stopping 5-6 ft from the eaves..probably letting heat in..

 

[Dapph2]

the moisture will still get into the loft, can you pull one down, and see if you can add a plantpot / pot noodle pot?

Check the down lighters are LED halogen ones are 50 watts of heat and will quickly melt a pot noodle plastic . When I had Halogens in my last home I made conical dunces hats out of half chicken wire to just pek an h-ing=ch above the void insulation . This place was filled with sunken Halogens 23 in all .. the TWA ...errrr Gentleman who put them in had also used a hole saw and cut through six roof trusses two entirely . where they touched the wood of the trusses all had sever charring evidence and cooked uninsulated with silicone wires .



WRT moisture . get as much moisture out the air as possible . drying clothes on rads , having long hair , using a shower or a hair dryer leaving bath towels to dry all put a lot of hidden water into the air Long hair ..use a simple micro fibre cloth as a flannel and mop the hair almost dry wring out the cloth so the water goes down the plug hole .. same after a bath or a shower . Bin one use nappies in a tied off bag and re useable ones in a lidded bucket .

Cook to boiling point with a lid on then turn off the gas if possible to let it cook on the residual heat . if possible though some things will need a gentle lidded simmer .. Gas ovens *& hobs also produce condensation


This is an indication of how much water there is in your home .. even breathing adds to it.


At 19°C, the maximum moisture content in a cubic meter of air is approximately 17.3 grams of water vapor at 100% humidity. This means that at this temperature, the air can hold about 17.3 grams of water if fully saturated.
https://www.bing.com/ck/a?!&&p=eab1...XN0dXJlLWNvbnRlbnQtYWlyLWRfMTQwMy5odG1s&ntb=1
60 % humidity @ 19 oC is considered reasonably normal and holds 14 gram per cubic metre .

It cost a lot to heat the extra moisture 24/7 say you're heating 250 cubic metres x 17.3 - 14 = 3 grams x 24 hours 7 days a week ....... 250 x 3 x24 about £ 4.50 per day or £31 a week £ 91 in 3 weeks the price of a Screwfix dehumidifier .

We have our Screwfix £95 dehumidifier plumbed into a waste pipe and run a humidity of 55 % @ 19 oC most of the time

 

[gaz1]

i dont know the size of eaves you have there is the slot type or there is the circle type

you need 4 2 on either side for a flow through

as goes for trap door add some insulation on it pack a spacer and then screw across the spacer

 

[minimutly]

If the house is above a certain height, subject to Westerly winds carrying moisture you will have this issue, irrespective of any "leaks" from below. Absolutely they should vent the house every day, mornings are good, but really a dehumidifier is a must between Oct and March. You can vent the loft all you like, if the air coming through is laden with moisture you will, from time to time get condensation up there.