# Humidity problem - possible cause(s) and report attached - request to answer two questions



## van_suso

Hello,

I've been living in my current apartment since December 2016. In the first two years of my living here, the owner repainted the surface but he stopped since 2019. He did install a VMC.

Now, the surface of my bathroom walls have been damaged due to moisture, and I'm attaching a screenshot of the relevant part of the report from the plumber sent by my insurance - it shows that condensation is the problem behind the corrosion (there's no internal leak in the wall) - please see the screenshot below. Note that I've a VMC and I use it every time I shower and the only large window in the bathroom is mostly kept open unless there's freezing cold outside. Despite all that, there's huge dampness/humidity and it's corroding my calls. 

I wrote to my landlord about possible repair, but he replied stating that he never had the dampness problem before me, so essentially I'm responsible for the humidity. I'm quite confused how the humidity could build up like that? Could it build up over the years? My landlord bought the apartment in 2015 I think and he had a renter before me in 2016 and back then there was no such visible effect.* 

(1) I'm guessing back then it was a brand new apartment, and with the passage of time, the humidity gradually built up? If yes, this could explain why there was zero effect of humidity during the previous renter's time, but after a few years, it started to show its effect. Could this be true at all?*

*(2) I was wondering whether whose responsibility it'd be to take charge of this repair: the landlord's or mine?*
Thank you!


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## suein56

Being unable to read the conclusions properly as they are hidden I would hazard a guess that your landlord might have used the wrong paint on the walls ..
It doesn't sound as though a VMC has been installed as they run 24 hours a day .. has an extractor fan been installed ?


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## BackinFrance

If the temp of the room is only 15 deg, the steam from your showers will certainly end up running down the walls unless you have a good air current functioning in the room until it has dried out, and that will take some time after each shower.

I can't see much of the inserted photos, only page 1 and not all of that.


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## boilerman

BackinFrance said:


> *If the temp of the room is only 15 deg, the steam from your showers will certainly end up running down the walls* unless you have a good air current functioning in the room until it has dried out, and that will take some time after each shower.
> 
> I can't see much of the inserted photos, only page 1 and not all of that.


This is true, condensation starts when warm air hits cold air, or cold surfaces. As BIF said ventilation is the key, you need a good fan, or the landlord does, its his property that's going to deteriorate.

Sorry if I sound like a smartarse, but our bathroom in the UK is tiled, floor to ceiling,(cold surfaces)its always warm in there and there's a very good extract fan in there. The window is rarely open, as fresh air, is moisture ridden, and not as warm as we think sometimes. We don't have condensation problems


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## BackinFrance

Perhaps the bathroom needs to be better heated and showers taken at a lower temperature. The greater the difference between ambient room temperature and the temperature of the water you use to shower = more steam and condensation.


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## boilerman

Just a bit of light reading for you Van

Dew Point Definition for Home Owners (eco-home-essentials.co.uk)


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## tardigrade

Using a bleach solution, clean the affected painted surfaces. Let dry. Re paint with a paint of your color choice that is suitable for kitchens and bathrooms.

Unless you can prove the landlord painted with inferior paint; I think it is up to you to solve and rectify the situation.


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## van_suso

BackinFrance said:


> If the temp of the room is only 15 deg, the steam from your showers will certainly end up running down the walls unless you have a good air current functioning in the room until it has dried out, and that will take some time after each shower.
> 
> I can't see much of the inserted photos, only page 1 and not all of that.


Thank you for your reply, let me do some thinking. In the meantime, I'm attaching the conclusion so that you see it clearly.


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## van_suso

suein56 said:


> Being unable to read the conclusions properly as they are hidden I would hazard a guess that your landlord might have used the wrong paint on the walls ..
> It doesn't sound as though a VMC has been installed as they run 24 hours a day .. has an extractor fan been installed ?


Hello,

Thank you for yur reply. I'm going to answer, but in the meantime, let me attach the conclusion properly, so you see it clearly:










As for your question whether an exterior fan has been installed, I can only see a small VMC on the wall opposite to the wall where the shower is, and the distance between these two walls is about 1.8m-2m (180cm - 200 cm) meter I'd think. Note that the part of the wall that's more severely damaged is the one directly attached with the shower, and the far from the shower we go, the less severe the damages on the walls become. But on the other hand, the VMC (not sure there's an exhaust, perhaps there is, a small fan moves each time I turn on the VMC), is about 180cm-200cm away from the shower. *My question is: do you think that because the VMC is far, it won't have much effect on protecting the shower walls?*

Also, prior to the report, my insurance company wrote these exact words: "_Lors de cette intervention, le sinistre est dû à un phénomène de condensation liés à un default de VMC_." While I roughly understand what it means, does it mean that the VMC (the fan that runs and is responsible for effective air circulation) is not working properly/needs to be replaced/needs to be repaired/needs to be placed somewhere else? Could you please let me know?

I also didn't understand the part of your reply that says "It doesn't sound as though a VMC has been installed as they run 24 hours a day ." 24 hours a day? I run the fan in the bathroom during my ten minute shower plus another ten minutes. I'm just not sure why they'll run 24 hours though, but I'm sure I'm missing something here.


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## tardigrade

Mechanical Ventilation | VMC | ECOCLIMA Padova


Ecoclima, Padua-based company with 25 years of experience in the air treatment sector, develops systems for the mechanical ventilation ventilation air and ventilation systems VMC.




vmc.ecoclima.com


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## BackinFrance

tardigrade said:


> Mechanical Ventilation | VMC | ECOCLIMA Padova
> 
> 
> Ecoclima, Padua-based company with 25 years of experience in the air treatment sector, develops systems for the mechanical ventilation ventilation air and ventilation systems VMC.
> 
> 
> 
> 
> vmc.ecoclima.com


The OP lives in an apartment, not only that, he does not own it, he rents it.


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## van_suso

BackinFrance said:


> The OP lives in an apartment, not only that, he does not own it, he rents it.


Thanks, there has been a new addition to the story. While my owner denied that there was no condensation problem before me, with other tenants, the tenant before me wrote to me that there was condensation although not too severe and it was detected by an expert intervention and the reason was a leak from a neighbor's apartment. So it seems like my landlord didn't disclose this to me.


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## tardigrade

BackinFrance said:


> The OP lives in an apartment, not only that, he does not own it, he rents it.


This is the answer to the OP asking "what is a VMC". 

Is that ok for you?


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## BackinFrance

tardigrade said:


> This is the answer to the OP asking "what is a VMC".
> 
> Is that ok for you?


That is not just any VMC.


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## boilerman

How do I know what size bathroom extractor fan I need?


*"This is calculated by multiplying length by width by height. Let's take an average measurement: 3m long x 2m wide x 2.4m high = 14.4 cubic metres. This means that in order to change the air in that room once an hour, a fan would have an extraction rate of 14m3/h."
This information would be on the internal workings of the fan, somewhere you shouldn't be. (as its not yours)😉

There is also the amount of water a shower produces(and the temperature)
An electric shower uses between 3 and 10 litres per minute
An unvented cylinder(white tank fixed to a wall type)(most likely across europe)could be double that, but this is product specific, its just a guide. There's showers, shower heads, pipework size, Tank type, boiler type, in fact loads of variables involved.
From what I've understood so far, the air extraction rate in the shower room, seems a little low, but this is all guess work, from afar

Best of luck with it, but beware of stories from other tenants, they can be embellished just for effect.

If you get it sorted, can we call you "Van the Man"🤣*


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## BoilingFrog

There is a very simple test to determine whether or not the wetness on a wall is from external water penetration through the wall or from condensation depositing _moisture on the wall_. If you encounter a situation where you need to determine what caused a wall to be wet you can follow the below steps:


Pick a test area on the wall and take measures to adequately dry the wall. This can be done with heaters or any other safe method that restores the area to a dry state.
Once dry, take a piece of aluminum foil and tape it onto the wall in the area that you have dried. Be sure to tape all of the sides so that you reasonably seal the air behind the foil.
Leave the foil in place for at least a day and then remove it. If the moisture is on the side of the foil facing away from the wall, it is condensation. If it is on the side of the foil facing the wall, it is penetration through the wall.
From: Basement Health Association


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## suein56

van_suso said:


> I also didn't understand the part of your reply that says "*It doesn't sound as though a VMC has been installed as they run 24 hours a day ." 24 hours a day? I run the fan in the bathroom during my ten minute shower plus another ten minutes. I'm just not sure why they'll run 24 hours though, but I'm sure I'm missing something here.*


A VMC is not what you have in your bath/shower room .. as a VMC runs 24 hours a day and there are usually outlets in the WC, the bath/shower room and the kitchen. You have an extractor fan which operates when you choose to use it.

The fan you have is not adequate for your shower room. Plus your shower room is too cold leading to excessive moisture on your painted walls. The walls cannot dry out as there is not enough ventilation.
Excessive condensation will lead to black mould on the walls quite quickly.

As recommended by others .. clean the mould with bleach; dry out the walls; then heat the room and increase the ventilation .. your landlord should replace the fan you have at present with a more efficient one vented to outside. 
I am assuming that there is no opening window in the shower room ?
Do you shut the door after you have had your shower or do you leave it open ?


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## boilerman

BoilingFrog said:


> There is a very simple test to determine whether or not the wetness on a wall is from external water penetration through the wall or from condensation depositing _moisture on the wall_. If you encounter a situation where you need to determine what caused a wall to be wet you can follow the below steps:
> 
> 
> Pick a test area on the wall and take measures to adequately dry the wall. This can be done with heaters or any other safe method that restores the area to a dry state.
> Once dry, take a piece of aluminum foil and tape it onto the wall in the area that you have dried. Be sure to tape all of the sides so that you reasonably seal the air behind the foil.
> Leave the foil in place for at least a day and then remove it. If the moisture is on the side of the foil facing away from the wall, it is condensation. If it is on the side of the foil facing the wall, it is penetration through the wall.
> From: Basement Health Association


Nice trick that


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## BackinFrance

boilerman said:


> Nice trick that


Done properly it could set the OP's mind at rest.


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## BackinFrance

suein56 said:


> A VMC is not what you have in your bath/shower room .. as a VMC runs 24 hours a day and there are usually outlets in the WC, the bath/shower room and the kitchen. You have an extractor fan which operates when you choose to use it.
> 
> The fan you have is not adequate for your shower room. Plus your shower room is too cold leading to excessive moisture on your painted walls. The walls cannot dry out as there is not enough ventilation.
> Excessive condensation will lead to black mould on the walls quite quickly.
> 
> As recommended by others .. clean the mould with bleach; dry out the walls; then heat the room and increase the ventilation .. your landlord should replace the fan you have at present with a more efficient one vented to outside.
> I am assuming that there is no opening window in the shower room ?
> Do you shut the door after you have had your shower or do you leave it open ?


He has a window which is almost always open and perhaps or very likely contributes to the problem. I have no idea at what time the plumbe (?) came, but at that time the temperature in the bathroom was only 15 deg. Of course we have no idea at what time the OP takes his shower. It is unfortunate that in France extractor fans in a bathroom are often referred to as a VMC. Nonetheless a tenant is required to take appropriate care of the property and it appears that the OP's insurance has denied his claim. 

I think if the OP wants his landlord to either take responsibility or partial responsibility, he would do best to seek advice via his assurance juridique given there are all sorts of issues with evidence.


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