Loft condensation (measures taken)

[tmasa]

Hi all,

~30yo detached house
Loft insulation topped up from 100 to 270 about 10 years ago.
Central part is boarded, sides are not.
Had no problems with condensation until last couple of years.
The only variable that changed, I think, is amount of junk stored there (lots of boxes)
When recent cold weather started had small pools of water on top of things in the centre.
-----
Removed a car's worth of flattened boxes from there
Rearranged other stuff to leave gaps
Insulated hatch (only small perimeter gap ~1cm left around)
Put 10 felt vents + 20 alternatives
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After few days no more pools, but still lots of droplets and slightly wet stuff in the middle

Climate wise:
- was little wind last week, today it picked up didn't check on droplets yet
- temperature in loft seems to stay 2-3 degrees above outside
- humidity stays around 90 at night and raises to 94 during the day (was 85-92 outside these days)
- the house itself is relatively dry ~50 humidity, tumble dryer used, combi boiler heats to 19 day / 15 night
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Some questions:

1) Is it everything that I could have done DIY to resolve it ?
2) Do I just wait weeks (?) for new setup to start working, how do I monitor it .. just number of droplets visually ? Have temp/humid monitor installed, but not much point with 90 humidity outside.
3) I can see eave vents on one side, but not in the front where there are 2 brick gables - hidden/something else/missing ?
4) I don't really get how felt vents work - they do open felt sheet end, but it is stuck in the middle, so no free airflow still. And looking where eave vents are installed, how does air gets inside at all, it would just go under felt rather than through ?

Thanks!

 

[JohnD]

Show us your eaves gaps.

Do you have holes in the ceiling, e.g. for downlighters or pipes?

How is your bathroom ventilated?

Is your loft hatch sealed?

 

[tmasa]

Eave gaps are on the 3rd picture and loft hatch is now sealed (2nd paragraph).

Bathroom is ventilated by opening window after shower/bath

Should be some tv aeriel / lighting holes which are covered by insulation.

Some small holes that led to the old water tank in the loft, now obsolete.

 

[Harry Bloomfield]

4) I don't really get how felt vents work - they do open felt sheet end, but it is stuck in the middle, so no free airflow still. And looking where eave vents are installed,

Idea is, to raise the overlap of the upper, push the lower one down, thus creating a gap through which air can flow through the tiles and out. If the over lap is too great, then the usual felt vents will not work, instead - see if you can poke something long down, like a two bits of 20mm plastic conduit, or even a bit of timber.

Condensation in lofts, is a result of warm, moisture laden air, from the house, making it's way up into the loft space. Once there, it condenses out on the cold surfaces, unless there is adequate ventilation for it to escape.

 

[JohnD]

Eave gaps are on the 3rd picture

It's too small, I can't see the gap.

 

[JohnD]

Should be some tv aeriel / lighting holes which are covered by insulation.

Some small holes that led to the old water tank in the loft, now obsolete.

Mineral wool is not airtight

 

[tmasa]

here is a bigger picture, but the angle might not be the best .. it is around 6-8 inch gap, maybe even too much

 

[Harry Bloomfield]

here is a bigger picture, but the angle might not be the best .. it is around 6-8 inch gap, maybe even too much

The point is, is there a good air flow through the gap?

 

[tmasa]

Mineral wool is not airtight

There are maybe 5-6 small holes, and this didn't change over last 10+ years as well as rock wool insulation .. had no condensation issues before

 

[tmasa]

The point is, is there a good air flow through the gap?

How do I measure if it is good ? Should there be any draught if there is no wind outside?

 

[JohnD]

here is a bigger picture, but the angle might not be the best .. it is around 6-8 inch gap, maybe even too much

Presumably taken at night, as no daylight shows through any gap? (I can't see a gap)

 

[Harry Bloomfield]

How do I measure if it is good ? Should there be any draught if there is no wind outside?

Candle, cigarette smoke, piece of tissue...

 

[tmasa]

Candle, cigarette smoke, piece of tissue...

Wouldn't use open fire even with all that humidity, but I do vape, will try. What creates draught if there is no wind, pressure is the same ?

 

[tmasa]

Presumably taken at night, as no daylight shows through any gap? (I can't see a gap)

Yes, trying to sort it out after work, will try to get a better picture over the weekend.
Any idea about those gable (or whatever it is called - triangle brick structures above windows) sections, is it it supposed to have any vents there ?
Being double it takes most of the front and the beams look more wet on that side, but that could also be because North facing.

 

[Harry Bloomfield]

Wouldn't use open fire even with all that humidity, but I do vape, will try. What creates draught if there is no wind, pressure is the same ?

Your vape will do it even better

Even with no wind - Heat from the house will rise, and exit through those vents if they are working.