Running an extractor fan for long periods (damp cellar)? (2023 Update)

[Stuart Noble]

Yes, it's all compromise but I would think air bricks in the cellar would be the equivalent of having all the windows in the house wide open.

[Adam Funk]

Mine was a lot drier when the dehumidifier was running too.

Good one.

[Fash]

Perhaps it's underground or something! Who can say, I guess it could be one of those above ground cellars, but they seem to be getting ever so rare these days.

Did it never occur to you that rain sometimes falls on the earth making it damp on the outside of the cellar and maybe (just maybe) some of this water is coming in hence the damp! Alternatively could be a damaged downpipe, one of those ones that reaches the ground and then just carries on down!

Fash

[Adam Funk]

YMMV, but in my experience, the cellar was a lot drier with a running dehumidifier (and the bother of emptying the tank every day) than it is now (with a few air bricks, but no fan or dehumidifier).

[Adam Funk]

[Adam]

I eventually found a dehumidifier with a built-in pump at a large B&Q. It was £200, which sounds like a lot, but I thought it wasn't too bad in comparison with the prices of a decent dehumidifier and a separate pump, plus the work to fit the two together.

It's a "three-way" model: you can (1) unplug a drain hole in the back to run the water away by gravity, (2) leave it as it comes to empty the

6-litre tank by hand, or (3) plug the inlet into the tank to get the pump to run whenever a (presumably much smaller) tank inside fills up.

The pump has a maximum head of 1.65 m. I slightly underestimated the height of the air brick I wanted to run the hose out through, so I ended up putting the dehumidifier up on a heavy-duty shelf. It mysteriously leaked a lot of water one evening right after I'd moved it there (and let it settle for over an hour before plugging it back in, although that's to protect the compressor rather than the pump, AIUI). So I switched it off, looked to see if I could figure out where it was leaking, gave up, and tried again later --- it has worked fine since then.

The cellar is now drying out reasonably well after something like two months of accrued damp with no dehumidifier. Unfortunately this dehumidifier, which is rated at 60 litres/day, draws 600 W (and increases the temperature down there by 2 or 3 C) when the compressor and fan are running (I doubt the pump adds much more).

I've turned the humidistat back from "full blast" and will consider running it on a timer for E7 too.

[Ian Bowden]

replying to Stuart Noble, Ian Bowden wrote: The only proper way to dry (and maintain) a cellar is *ventilation*. You should draw air in one end and pump out at the other if you do not have any other method or form of doing so.

[tabbypurr]

a) wrong b) 13 years too late

[Brian Gaff (Sofa 2)]

Yes must have been home owners club again, but I've blocked a lot of those. Brian

[sarah burgin]

replying to Ian Bowden, sarah burgin wrote: Hi Stuart, do you have a recommendation for a good supplier please

[Paul]

And your recommendation would be?

[Damian]

A dehumidifier uses much more energy than a fan. My dehumidifier uses 330 Watts on low, a fan is usually less than 10 watts

[Davey]

13 years is certainly long enough to test the endurance of the fan.

[tabbypurr]

No, it uses more power than a fan. What matters is energy, not power.

NT

[Vir Campestris]

Yes, but...

An extractor fan is taking warm air from your house and throwing it away. This is being replaced by cold air from outside.

That's likely to be a lot more than 10 watts.

A dehumidifier is using (in your case) 330W, but that all ends up inside the house. In fact even more than that ends up in the house, as you get back the latent heat of evaporation of all the condensed water.

Andy

[tabbypurr]

and the fan must run for far more time to get less effect.

NT

[zz-james]

any thoughts on using MVHR to ventilate a cellar?, these have heat recovery.

[Fredxx]

All of your questions are answered here:

[Ernie J]

Yes, I have a 9" industrial fan in my cellar, that is programmed on via a Hive plug. The cellar also has my server and IT kit, which produce tens of watts of heat. This cellar is about 16 deg most of the time, and nothing gets the dreaded blobs of mold growth. My other cellar is a work in progress, this has 2 air bricks, where the coal used be thrown in, but I plan to put a similar system of mechanical extraction from the floor level to the outside world. I just need to find the right system!

[Animal]

Sounds like you need to monitor temp & RH indoor & out, and a small computer could control it. That way it can give you warmth, coolth or dryness as required.