Ceiling condensation problem

[newstarnord]

Hello, here we have a house with an unused basement, living rooms, and upstairs.

- The basement is not heated but it is permanently 17 ° because the boiler heats the rooms (boiler pipes not very well insulated)
- The living rooms are currently at 19.5 ° with 68% humidity.
- The first floor is not heated and is made up of two parts: a part not insulated at ground level but with wooden floor with space above the joists / slab / concrete slab floor. This part of the floor although not being heated is at 18 °. It must be said that this part is well insulated at the level of the walls and receives a significant exposure to the sun given its small volume.
- The floor also consists of an unheated part on a concrete slab also whose current temperature is 12 ° with 68% humidity and this is where the problem occurs

This part of the floor is insulated at ground level, but very poorly; I distributed the glass wool in a roll but as we walk on it there are lots of thermal bridges, the glass wool is damaged. I also insulated a little with polystyrene but here too the polystyrene is damaged. I have dampness that has appeared in one of the bedrooms in the living rooms. I understood that the dew point being 12 ° for an air at 19.5 ° with 68% humidity, the problem came from there.

What would be the solution that would allow us to remove this condensation without heating the floor?
You should know that this floor has a ceiling that is six meters high. On the other hand, the roof, it is well insulated a priori (20 cms of rock wool).

If I put a centimeter of vermiculite or perlite upstairs, rather than this poor insulation at ground level, could that solve this condensation problem?

We should be able to walk on this insulation without destroying it.

[Obamot]

Hello,

Welcome!

Why is this concrete slab so cold? Is there a garage below?

Well insulated at wall level, is it facade insulation?

Would you like to climb a false floor?

Photos is possible? (With details of critical points).

RTDC.

[Christophe]

What would be the solution that would allow us to remove this condensation without heating the floor?

68% humidity is too much in the living rooms! You need to investigate the source of this moisture ... the roof? wall infiltrations? Hair lifts? Invisible plumbing leak?

If the source is not found, perhaps installing a dehumidifier can improve comfort without being too expensive: it is better (= this will consume less energy for the same comfort) to lower the RH by 20% than to increase the heating temperature by 2 ° C (I'm schematizing but that's the idea ...)

[newstarnord]

It is that we do not have VMC and the kitchen hood is a recycling hood.
We just have two air extractors in diameter 100, they each extract about 90 m3 / h.
We should be running them all the time, maybe?

And, even if we open the windows from time to time, the temperature being quite high outside (around 13 ° on average) and the humidity high also outside (85% lately, it's been raining almost two weeks) , the hygrometry does not go down that much.

What would be the solution that would allow us to remove this condensation without heating the floor?

68% humidity is too much in the living rooms! You need to investigate the source of this moisture ... the roof? wall infiltrations? Hair lifts? Invisible plumbing leak?

If the source is not found, perhaps installing a dehumidifier can improve comfort without being too expensive: it is better (= this will consume less energy for the same comfort) to lower the RH by 20% than to increase the heating temperature by 2 ° C (I'm schematizing but that's the idea ...)

[GuyGadeboisTheBack]

If he lives in a humid region and his home has no ventilation (active or passive), this humidity level can be understood, but yes, 68% humidity is too much.
Edit: toasty, 85% humidity outside!

[newstarnord]

Thank you for your answer.

No, the first floor (the non-habitable part) is not well insulated at the level of the walls: the two brick gables open directly to the outside.
Ok I'll see if I can send pictures.
The living area is on most of the walls insulated with vermiculite.

I have for project to make a floor but unfortunately at the moment this is not possible.

Hello,

Welcome!

Why is this concrete slab so cold? Is there a garage below?

Well insulated at wall level, is it facade insulation?

Would you like to climb a false floor?

Photos is possible? (With details of critical points).

RTDC.

[newstarnord]

If he lives in a humid region and his home has no ventilation (active or passive), this humidity level can be understood, but yes, 68% humidity is too much.
Edit: toasty, 85% humidity outside!

Currently the outdoor humidity level has dropped a little, the sun has returned: 71% for 11 ° so if I ventilate, it should finally drop.

But when the rate is at 85% for say 15 ° will my air extractors act effectively or not?

[Adrien (ex-nico239)]

The most ecological and the most beautiful moisture absorbent is very simple and it is nature that provides it ... the fern and in particular the Boston fern ...

However, this is not the only one: plants are a good way to beautify your interior and solve the problem.

Why not give it a try?

[Ahmed]

This concrete slab is probably the cause of a massive thermal bridge at the walls and an insulating floor will not solve this point.

[GuyGadeboisTheBack]

Always beware of a concrete slab ...