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Hi guys,

I'm having to deal with an ongoing issue in the basement. This is a semi-detached property built around 1935.

Basically we have 2 air bricks and 1 old vent within a window in the basement approx 1.8mtrs from floor. I know this might sound obvious, but they are all above outside ground level.

If you closely take a look at the images I've attached, you'll see that the air bricks have water dripping around the borders of the bricks. The air vent in the window also has dripping water at the bottom.

The humidity in the cellar is 90-100% and it is very cold. The walls are only slightly damp at around 1 foot from floor, but this I believe this is due to the outside ground level being higher, which I guess has to be expected. The rest of the cellar walls seem pretty dry.

However, I'm wondering if there's plenty of air circulation, then why am I getting this issue of condensation?

Can you please suggest anything to help reduce or resolve this?

Thanks in advance for your help.

Can you see daylight through the air bricks, and are they on opposite sides?

Yes I can see daylight and yes they are directly opposite on the outside wall

The weather at the moment is wet, and cold. The air bricks are letting cold air in that are making the walls cold and condensing moisture out of the air. The ventilation rather than helping is making the problem worse by bringing in more cold and wet air.

Thanks rorschach.

Your theory totally makes sense, but what would you suggest in order to reduce this?

For a warm and wet climate like ours I am a proponent of sealing up any vents and air bricks and running a dehumidifier to keep things dry. It works very well above ground but basements can be tricky though if there are walls below ground, you can get water coming through the walls themselves.
If I were dealing with a basement I would seal the vents temporarily at first and see how it goes before making it permanent.

I can do that by using a plastic cover and some duct tape, but would I need to seal the vents on both the inside and outside or just the inside?

Inside would be fine for testing purposes, doing it outside would be tricky I imagine but if you can do it, do both.

I can do both... I'll use duct tape for the test.

I'll try and do this now. Just not sure how long I'm supposed to leave it for and what should I look out for in the cellar.

Just realised, that unfortunately, I can't seal the outside due to the vent in window being difficult to cover. I guess I'll just have to cover it on the inside.

It could takes weeks for it to dry out with the dehumidifier running, but as I said you may have water coming through the walls themselves.

I would think though that you should start to see a difference in less than a week, certainly you will quickly notice if there is less condensation and a lower overall humidity.

To be honest Rorschach, I'm not in too much of a hurry, so I guess I can wait a week or two.

Can you recommend any dehumidifiers that are reasonably cheap to run?

What surprises me is that in total the house has 7 air bricks/vents!

2 at front of house
2 at back of house
4 at side of house (3 of these are in this cellar and 1 is for the kitchen extension)

....that's a bit too many IMHO, but I could be wrong. If you look at the air bricks, they definitely are not original and have been added more recently by the previous owner, which I find very unusual.

I never understand why someone would install airbricks now when everyone is trying their best to make their homes more efficient.

Rorschach wrote: ↑Sat Oct 26, 2019 10:51 pm I never understand why someone would install airbricks now when everyone is trying their best to make their homes more efficient.

I assume it's to keep the place ventilated to avoid issues like rotting and condensation. But don't you think my case it's been overdone?

ripperuk wrote: ↑Sun Oct 27, 2019 10:56 am

Rorschach wrote: ↑Sat Oct 26, 2019 10:51 pm I never understand why someone would install airbricks now when everyone is trying their best to make their homes more efficient.

I assume it's to keep the place ventilated to avoid issues like rotting and condensation. But don't you think my case it's been overdone?

That's the theory but it doesn't work as the ventilation lets in cold wet air which causes condensation. It also means any heat that you do produce gets sucked right out again, it's like running your heating with your front door wide open.