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Am I going to have mould issues?

fun loving criminal

I moved into a new flat recently and have a humidity and temperature meter.

Normal relative humidity levels in the flat seems to be above 70%. Dehumidifier works to get it down. But quickly increases again once it's turned off. I know anything above 70 and I can have issues with mould, so I would like to prevent it from happening in the first place.

When I viewed the flat, it was just painted, so it kind of hints at painting dirty mouldy walls but not sure.

I really don't want to move as it's so hard to find a place.

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houseyhouse

To keep the humidity down you need to ventilate the flat. The humidity in our bedroom is often close to 70 in the morning but after leaving the window open for a couple of hours it reduces.

fun loving criminal

https://www.boards.ie/discussion/comment/118601509#Comment_118601509

That is very weird, I like windows open, even when sleeping and humidity doesn't go down. Only a dehumidifier seems to help. It would be great if opening a window would help.

fun loving criminal

Emma2019

I think anything over 60 is a risk for mould.

But if your walls are always warm enough moisture won't condense. That's just unlikely unless you have the heating on all the time.

How much are you opening the windows. A crack helps but having them wide open for a bit each day is more helpful I think.

SupaCat95

I would advise you to move. My friend moved into a house with mould. It aggravated her Asthma, and she had to be hospitalised. I was in accommodation twice with mould. Now I wasnt sick because of the mould but I lost clothes and books. Both were miserable accommodations due to cold and damp. If you cant do that invest in a medium dehumidified, buy damp traps, ventilate every day. Use either Clove oil or tea tree oil on mould or potential mould sites.

fun loving criminal

https://www.boards.ie/discussion/comment/118603378#Comment_118603378

Where can I move to considering there's not much out there? This shouldn't be the best that I could find.

I use a dehumidifier but as soon as it switches off, it goes straight back up again. And I'm not doing anything crazy that produces more moisture. Not drying clothes inside, use extracter fans while cooking and in bathroom. Have a few of those chemical dehumidifiers around the place.

Just trying to figure out what I can do with such high levels of humidity? Or is this even my issue to fix? I'm not that long in the place, so this was definitely something that happened before I moved in.

houseyhouse

Are there vents in the bedrooms for ventilation?

fun loving criminal

https://www.boards.ie/discussion/comment/118604163#Comment_118604163

No vents but I leave window open

fun loving criminal

I know I'm going to end up with mould with readings like I'm getting.

Really don't know what to do. Is this something I have to manage or is this the responsibility of a landlord? I know a landlord will probably pass it off as a tenant's issue like not ventilating the place, drying clothes indoors (which I don't do).

Not sure what to do.

houseyhouse

Rental properties are required to have vents in the bedrooms for this reason. You could ask about putting some in. Really depends on how decent your landlord is. Is it expensive/annoying to run the dehumidifier all the time?

Seth Brundle

There is something causing the high humidity.

If you have adequate ventilation then the humidity levels should decrease. That you seem to have the dehumidifier on and the humidity levels rise as soon as the dehumidifier switches off suggests a lot of moisture coming from somewhere.

If you aren't drying clothes, is there any other machines that use water?

Is your bathroom drying out fully after you shower?

Is there any damp in the property? Is it a basement, ground or above ground flat? Any weird smells?

Ray Palmer

https://www.boards.ie/discussion/comment/118604674#Comment_118604674

No it is so you don't suffocate in the event of gas leaks. All property requires it not just rentals. Many windows have in built vents that cover the requirement.

Opening a window at this time of year will not reduce moisture in a property it will increase it. There is litterally no property in Ireland that doesn't suffer from our moist climate. The increase in building tightness makes the issue worse over the decades. Drying clothes inside is the biggest cause. You have to clean to stop mold and that is not going to change no matter the property.

fun loving criminal

https://www.boards.ie/discussion/comment/118604708#Comment_118604708

First floor flat. I can't think of anything else using water except the washing machine and kettle but the kitchen seems to have a better relative humidity than the bedroom!!

I leave the extractor fan on in bathroom for a while after I shower and the misty mirrors clear up quickly enough.

I don't have a clue where the moisture is coming from.

J_1980

I had 70% in bedrooms and 60% elsewhere.

now running a dehumidifier 8h a day and its mostly at around 40%. 45-50% in bedroom in mornings.

the apartment is airtight like a newbuild (professionally tested) and I keep windows generally closed (to keep at 23.5 degree inside).

J_1980

Another way to check: does humidity go up when you’re away for longer period?

if yes, there is something wrong

spaceHopper

What is the humidity outside, if it's high then what good will ventilation do. Was it empty and cold for a long times? will it get better as it warms up. Are using a gas fire?

fun loving criminal

https://www.boards.ie/discussion/comment/118605301#Comment_118605301

It was empty for at 6 weeks because I got a letter from the ESB telling me that no one has electricity in thy flat for 6 weeks and electricity supply was going to be cut off.

Not using gas fire.

fun loving criminal

https://www.boards.ie/discussion/comment/118605249#Comment_118605249

A tip I read online, on some website was to switch on the heating and open windows at the back and front of the house for 10 minutes. So I done that and got humidity down to 55% which stayed like that for a bit without jumping. So I'll see what's it like when I get home from work later on. I just don't want moisture and mould to ruin my stuff. I'm almost considering putting my valuables into storage.

10-10-20

https://www.boards.ie/discussion/comment/118604876#Comment_118604876

Hold off on that generalisation!

Warm air has a higher vapour capacity than cold air, so even 'damp' cold air at 69% RH @ 8 degrees C (such as today) will have a ratio of 4.587g per kg of vapour by weight. That same air containing 4.587g of vapour now warmed to 20 degrees C will have a RH of 31.62.

So even on a freezing (0 degrees C) day where the RH is at 100%, the vapour load will be a tiny 3.77g/kg. This would indicate that it's generally better to open a window to allow some diffusion of the internal air, even in winter.

Ray Palmer

https://www.boards.ie/discussion/comment/118606192#Comment_118606192

Maybe in a lab but a room in a house is different. Are they going to close the window the minute all is balanced for example? What about when it is raining? Is the rest of the air in the building going to stay out of the room?

Technically you are correct in science but ignored many real world elements.

fun loving criminal

From what I understand and all the googling I've been doing lately, warm air holds more water, when it's cold moisture ends up as condensation on walls and ceilings, so you need to heat up the place. But at the same time, you need to let this moisture laded air out. So a tip I read online, heat up the place once a day and open windows as well. I'm not sure if this alone worked as I left for work and switched off the heating but left windows open and cross ventilated by leaving doors open and it really helped and relative humidity stayed under 60% and it didn't jump to over 70%.

I really hope it's this easy to manage and this is all I have to do.

fun loving criminal

Or I hope that cross ventilating helps. It's also been quite cold and apparently colder weather will have less humidity. But if that's the case, under 60% relative humidity is normal so if this is what I'm getting when it's cold, it seems high to me.

fun loving criminal

Great, I definitely have a mould problem. Found some at the end of long curtains. I only picked up the keys three weeks ago and properly moved in last week. I'm not sure if I checked the end of the curtains when I moved in, so not sure if I had mould on moving in or not.

spaceHopper

Any post for the last tennant, can you contact then in any way? Stalk them on social media.... ask them if they had issues

Yellow_Fern

https://www.boards.ie/discussion/comment/118605036#Comment_118605036

Is the fan working? Hold a piece of toilet paper under it to see.

fun loving criminal

https://www.boards.ie/discussion/comment/118611078#Comment_118611078

I tried looking them up online already, ha

fun loving criminal

I don't understand, I'm doing everything right. Not drying clothes inside, opening windows, etc. I did have a few days with high humidity, so I was kind of expecting it. Even used the dehumidifier the night before last and humidity was still over 60 in the morning which is crazy after a full night of use. But for the past two days, I was able to get that humidity percentage down to under 60, which is alot better than over 70.

I don't know what I did to help it go down, was it heating and cross ventilation or is it the cold weather that's meant to be drier and less humid. If it's the weather, well that can change. If it's a case of heating and ventilation, that's great because I can continue to do that.

fun loving criminal

https://www.boards.ie/discussion/comment/118611600#Comment_118611600

Fan is working.

MicktheMan

It's both.

The internal RH% will track the external temperature very accurately i.e. when it's very cold outside (low single digits) the internal rh% will drop. This, however, is not in your control.

What is in your control is what happens inside:

Keep the moisture load as low as possible (e.g. not drying clothes indoors) and try exhaust the water vapour at point and time of production etc.
Keep the place warm. Warm air can hold a lot more moisture than cooler air and therefore allows a better and more efficient exchange of wet internal air with dry external air through your ventilation system or strategy. Dryer internal air will result in a dryer structure which will also mean dryer insulation. Dryer insulation will mean it's easier to keep warm etc
You need a ventilation system or strategy and it looks like your routine is a decent strategy.

If you moved into a "wet" structure due to the actions of the previous occupier or being vacant for a period what you are seeing may well be the structure actually drying out and by continuing to do what you are doing will keep the drying out process going.

10-10-20

Actually OP, what floor are you on in the complex and what's below you, and what's to your left and right? These spaces can have a significant bearing.