Damp cellar - more ventilation using a fan/humidstat system

hodd

Following on from this older thread...

https://forums.moneysavingexpert.com/discussion/4146361/solution-for-musty-mouldy-basement

All cellars get damp, and I've been researching into how to make mine (about 5m x 5m) suitable for storage of non-perishable items, i.e. I don't need a cellar conversion. At present, I have a portable dehumidifer down there which extracts about 25 litres of water a week.

I’m not a fan of tanking. The water outside has to go somewhere, and it’ll rise up and over the tanked surface or more likely through it. A surveyor suggested humidstat ventilators which would do the job of my dehumidifier on a permanent basis.

Does anyone have a humidstat ventilation system in their cellar? Any good? Who fits such things? I’m OK to spend a couple of grand on this.

Bigphil1474

OP, we had a damp cellar for years. We ended up just fitting an extractor fan which worked fine, but we had nothing like the 25l a week you have. Unfortunately it turned into a cellar flooded by ground water (about 9 inches) so ended up with a sump pump. We just googled a few basement conversion companies. I suspect they would do ventilation systems as well. 
We considered tanking and conversion but the £10-18k price tag put us off.

hodd

Thanks Phil, I only know it's 25 litres as I fitted a hosepipe to the dehumidifier outlet which drains into a jerry can which I have to carry up the steps every week! The dehumidifer probably makes matters worse as the floor dries out so more water seeps in. It's difficult to quantify in terms of relative humidity. Without the dehumidifier, it'd be damp but not like a sauna. As far as I know it's not liable to flood. 

This video is great. He has a couple of humidstat fans in his cellar and hasn't had to paint, tank or coat anything. I've asked if he can advise. Again, my fear is buying these fans, drilling huge holes and having them wired in only to find I still have to use the portable dehumidifier. I'm considering renting the property in the future, and I need a more robust cellar arrangement. I could leave it damp, but this will eventually affect the floorboads above.

https://www.youtube.com/watch?v=uxDvsAgCyrE&t=118s

Yes, and I've and a quote to install a membrane and drain/pump system and new floor - £17000 + VAT! I don't need a new floor. I like the cellar in the video

Eldi_Dos

Do the item's you intend to keep in cellar need to be kept at a certain humidity or are you just wanting a drier atmosphere in the cellar.

tacpot12

I have a humidity controlled fan in my bathroom. I installed it myself, but I am competent at electrical work and have the equipement to test any changes I make. I also know the Part P regulations and am happy to pay for anything that needs notification to Building Control do be done by a member of a Competent Persons Scheme. 

I used a E925 Humidistat from MS Electronics to control the fan. Any comptetent electrician would be able to install this for you. 

hodd

tacpot12 said:

I have a humidity controlled fan in my bathroom. I installed it myself, but I am competent at electrical work and have the equipement to test any changes I make. I also know the Part P regulations and am happy to pay for anything that needs notification to Building Control do be done by a member of a Competent Persons Scheme. 

I used a E925 Humidistat from MS Electronics to control the fan. Any comptetent electrician would be able to install this for you. 

Definitely. The electrician I use would be able to do this, but he wouldn't be able to advise on whether the fan was adequate. For bathrooms, a lot of websites show how to calculate fan rating based on the bathroom size. Also, while a bathroom gets steamy, it's not a constant ingress like you get from a cellar floor. Plus most, but not all, bathrooms have a window, and all have a door. Cellars might be closed and stagnant for days at a time. I'm learning this is the issue with victorian cellars which were more ventilated, e.g. with open coal chutes, and less so now.

There are no guides as far as I can see on how to size a fan for a cellar. I'd imagine there's also a space/mounting issue as cellars don't have exposed external walls. Maybe only a smaller fan can be fitted which may not be powerful enough. That would be a lot of time and effort and a lot of holes in brickwork for not much return.

I contacted the guy in the video. They offered some advice and maybe the fan company can advise.

hodd

Eldi_Dos said:

Do the item's you intend to keep in cellar need to be kept at a certain humidity or are you just wanting a drier atmosphere in the cellar.

Nothing fancy. The portable dessicant dehumidifer does the job. I can now store cardboard boxes down there as long as they're not in contact with the floor. The issue is I want to rent the property in a year or two. I cant expect a tenant to carry 25 litres of water up the steps every week. The dehumidifier is a temporary fix. I could leave the cellar to do its natural thing and leave it empty. It won't flood, but all that moisture will eventually affect the floorboards above. 

There are various grades of cellar usability right up to an office/living space. I just want to store non-perishable stuff. The guy's cellar in the video looks ideal. The orginal floor and walls are exposed, but he has two humidstat fans to create a draught. Unfortunately, he gives no details of how he calculated the power rating of the units.

Eldi_Dos

Most commercial basement area's I have been in kept the area dry by providing a continuous airflow through the area, usually by some combination of air bricks,vents or cowled vents,as its usual for airflow to be constant I fail to see the advantage of electric fans and humidstat control. The only times I saw fans used was in sealed plant rooms. If you do go for some form of vents take account of stopping rodents or wasps getting in by bonding some form of wire mesh over openings in cellar and an arid basement is normally quite chilly so may be worth some form of insulation between joists.

Advocado

The drier you make the air with a dehumidifier, the more moisture will move from the bricks into the air and therefore more moisture will wick into the bricks from the surrounding ground.

Without tanking it and stopping the moisture moving from the ground -> bricks -> air in cellar, the best thing is to just allow air flow.

But it'll never be suitable for storage of perishable items.  As you put stuff in there it'll prevent air flow to certain areas and so damp/mould will occur.

Advocado

The drier you make the air with a dehumidifier, the more moisture will move from the bricks into the air and therefore more moisture will wick into the bricks from the surrounding ground.

Without tanking it and stopping the moisture moving from the ground -> bricks -> air in cellar, the best thing is to just allow air flow.

But it'll never be suitable for storage of perishable items.  As you put stuff in there it'll prevent air flow to certain areas and so damp/mould will occur.

coffeehound

Advocado said:

But it'll never be suitable for storage of perishable items.  As you put stuff in there it'll prevent air flow to certain areas and so damp/mould will occur.

I used bricks to build ‘piers’ two courses high and sat pallets on top to keep stored items safely above the damp while allowing airflow.  Something else to do is ensure the access door is well sealed so that humidity doesn’t rise into the living rooms (though some will probably find other routes in).