Cellar mould/humidity!?

[Mjshipley]

Hi all,

Long time lurker first time poster here!

My name is Matt and I live in Stourbridge in the West Midlands, last year I bought a period property, built in the 1830s (we think) it's a three bed semi and has a cellar under my front room.

I've semi converted the cellar, (the walls are still bare). It was never a wet cellar previously and not really damp, only through the brick floor. (See some pics of before and now)










Almost 12months since my works and I'm starting to see some mould on the painted brickwork and plywood panel in the arch. (See pics). It's nothing drastic there are no droplets of water, just something I want to keep an eye on.



I'm struggling with the humidity also, it varies between 80-95% which even I know is way too high!

I have a window which I leave on trickle and a 5" extractor fan which is on a timer and comes on for 3 hrs per night, I've also got a radiator (connected to CH) down there which I just leave on no.1 and it hardly comes on.

Is this all wrong? Should I be sealing all gaps and going down the de-humidifier route instead?

Any thoughts would be helpful and apologies for the long first post!!

Matt

 

[88v8]

Hello and welcome to the Damp and Other Things forum.

Turning a coal cellar into habitable space is never going to be easy. With an rh of 80%+ there's a lot of damp air down there, just looking for somewhere cold to condense, currently it's on that arch. If you warm that up, it will condense somewhere else. Perhaps somewhere you can't see it, oooer.

Random thoughts:
The coal chute, is there still an opening at the top? That might be a good way to vent.
The extractor fan, in relation to the window..... the fan will pull air across the line of least resistance. If you want to move the most air then the opening needs to be the opposite side of the room to the fan. Otherwise the air will just go straight from the window to the fan.
You might also look at taking the ventilation from the house via a grille in the cellar door, rather than the outside, and close the window.
In the cellar, a fan heater, albeit costlier to run than a rad, will move air better. Even an oscillating desk-type fan would help in that respect.

But... all this will only move the air, not dry it.

I would not give up on the ventilation, but I would be inclined to add a dehumidifier to the mix. We have an Ebac 2650
http://www.dehumidifiersuk.com/ebac-2650e-18-litre-extraction-five-year-warranty-and-which-magazine-winner.html?gclid=CLKqmem3ssgCFavpwgod7T4P1Q
that I bought second-hand on eBay, although tbh they're cheap enough new.

At this time of year the house is at its dampest. Without the dehumidifier our cellar would be around 80/85% rh. With it running,the rh is c70%. Still not great, but no mould. It runs 24/7 about 8 months of the year, and always overnight - except when it needs emptying - no suitable drain alas.
And that rh improvement is with a cellar that is open to the kitchen, no way of closing it off.
It pulls out around a gallon every two days.

So, what I would do, I'd look again at your air movement/ventilation, and also put in a dehumidifier, timing it so it's on when the extract fan is not.

Ivor

 

[Mjshipley]

Hi,

Thanks for your detailed reply Ivor, very helpful! My only question would be about the de-humidifier, surely by attempting both ventilation and de humidifiying they kind of counteract each other? I don't want to be dehumidifying air only to have it extracted and replaced with more moist air! I guess this would also be the case if there was a vent in the cellar door?

Does that make some sense? I may have missed your point entirely!

Thanks again for your reply!

Matt

 

[88v8]

It's surprising, to me, that the dehumidifier in our cellar has such an effect. With the kitchen above, a large open stairwell and a short flight of stairs plus a powerful extractor fan in the kitchen, one would think that they would share the same atmosphere. But the 10% difference in rh shows it's not so.
However, it is true that we shut the cellar window at night and all winter. Hence, all air moved into the cellar by temperature difference and the circulation fan in the dehumidifier, is air drawn from the house.

To a degree, I think you'll need to experiment. To see what configuration of venting dehumidification and extraction best serves.

I do believe that a degree of new air entering the cellar is desirable, rather than just stirring the same fug.
Therefore, the extract fan seems a good idea. Clearly, there has to be an air inlet for the fan to work effectively, but during the winter at least, it might be my provisional preference to draw air from the house via the cellar door rather than from the outside. This on the assumption that the air from the house will be less damp that the external air .
I say 'provisional' because, as I mention, some experimentation may show otherwise.
It would indeed seem illogical though, to run the extract and the dehumidifier at the same time. I would rather envisage drawing in fresh air with the extract, and sucking out the mould spores, then drying the new air which in turn will suck damp from the walls etc, then blowing it out again on the next extract cycle. One has to remember that mould never sleeps, and if left to its own devices will happily resume colonisation. Moulds were here long before we were.

To avoid unvisible pockets of unstirred air, it might also be worth investing a few quid in a couple more hygrometers, so you can check that there are no damp hotspots. If there are, they can be attacked with an oscillating fan.

That mould on your wall is a reminder of how it was for our predecessors. Lacking our electrical armoury, their annual limewashing was not only decorative. The lime also killed mould.

Ivor

 

[Flyfisher]

I think this is just in the nature of cellars. As Ivor rightly says, it's how things were for our ancestors, so welcome to authentic period living!

I combat damp in our cellar with a dehumidifier. I take the point about ventilation potentially working against it but my experience is that without the dehumidifier I've had water droplets on all the floor (ceiling) beams and joists but with the dehumidifier there is nothing - so it definitely has an effect. The space 'feels' drier as well.

As for heating the space to reduce humidity, that may also be problematic because warm air can carry more moisture. I think of an untanked cellar as a space within an infinitely damp environment, I.e. the surrounding ground. If the cellar air is dried out, by whatever means, then the 'dampness gradient' will be increased, drawing more moisture into the cellar in an attempt to reach equilibrium. In practice, of course, it will be impossible to dry out the surrounding ground so there will always be a supply of moisture ready to move into the cellar.

Our cellar is quite small but the dehumidifier can fill a bucket of water within a couple of days or so, depending on prevailing conditions. It's common to have no drainage in a cellar so to avoid the need to constantly empty buckets, I use a 'condensate pump' designed for use with condensing boilers located in places with no drainage. Basically it consists of a small reservoir that collects water and when it reaches a particular level a sensor operates a small pump for about 10 seconds to empty the reservoir. I route the small outlet hose (about half-inch diameter) out through the cellar vent and into a surface drain. This arrangement means that the dehumidifier needs no constant attention. The condensate pump was about £30 and worth every penny.

 

[Keithj]

My guess would be that in winter, air drawn in from outside will be less humid in absolute terms - colder, so less able to take up moisture. Air from the kitchen will have the benefit of the steam from your kettle, your breath, etc.

I'd prefer a vent to allow air in from outside, with the option of closing it when it's freezing - for the sake of the cellar heating bill.

That said, the moisture permeating the walls from the ground outside will work hard to help you achieve 100% RH. The dehumidifier is the way to go. If it can discharge itself into a drain, so much the better.