Help me resolve this basement condensation nightmare....

[diyonly]

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.

 

[^woody^]

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

The humidity in the cellar is 90-100% and it is very cold.

You've answered your own question.

Heat holds moisture in the air. You don't have heat, and you have cold surfaces.

 

[diyonly]

Thanks woody. But is that humidity basically the outside air coming in? I do live approx 650ft above sea level.

I use the cellar to store diy tools, but these are all rusting away.

Since this is not a habitable room and heating would just go wasted, what's the solution? Would blocking up or reducing the air vents flow, help in warming up the place?

 

[^woody^]

The air coming it will be humid, but the moisture evaporating from the cellar walls and floor will be contributing too.

As an experiment, you could try an extract fan, one with a constant trickle setting, positioned so as to provide some cross ventilation, so that may involve some ducting to get it in the best position to ensure air is moving in all parts of the cellar.

An alternative would be to seal the vents and use a dehumidifier.

 

[diyonly]

That's much appreciated. I think the first cheapest way is to seal the vents and see how it goes.

But do you know what I can use as a temporary basis to do this? Also would I need to seal both inside and outside or just the inside?

Lastly can you recommend a dehumidifier for a large property?

Thanks.

 

[John D v2.0]

Lastly can you recommend a dehumidifier for a large property?

If it's a very cold place you have to use a desiccant one as the compressor ones won't really work well.

 

[^woody^]

But do you know what I can use as a temporary basis to do this?

Tissue paper and clingfilm normally.

I don't know much about dehumidifier types.

 

[diyonly]

Thanks John and Woody.

John - Yes, that's right, I've been searching online and desiccants are ideal for cold areas, whereas compressor types are suitable for rooms around 15C or more. Although my thinking was to go for compressor type and eventually move it into the house hallway as I have reasonably high humidity around the rest of the house too....65-80% in winter.

Woody - Tissue/clingfilm for sealing the vents? Aren't they a bit thin and won't the tissue become soggy?

Also what surprises me is that in total the house has 7 air bricks/vents around ground level (there's even more upstairs!)

The ground level has:
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 in the basement, they definitely are not original and have been added more recently by the previous owner, which I find very unusual.

 

[John D v2.0]

Thickness doesn't matter you only need to stop the draught. Just shove a plastics bag in the hole if that would work.

 

[diyonly]

Hi guys,

Sorry for the late reply. I had a bit of a disaster - I accidently smashed one of my double-glazed windows and have had to find someone to sort it out...still need to deal with it though.

Okay, so here's what I did....For the single-glazed window, I shoved a carrier bag as per John's suggestion into the round vent. For the air bricks, I had some spare kingspan pieces, so i cut them out and stuck them on with strong sealant....I've still left a tiny gap around them for a bit of air circulation. Currently the weather has picked up a little, so I'll have to wait and see how it goes. Just to clarify, I haven't blocked the air bricks on the outside.

The single glazed window though is still sweating condensation, so one option I'm thinking is to get a rigid-clear plastic board to stick on the outside....what do you think?