De-humidifier question

Fwom:Dorothy Bradbury ( snipped-for-privacy@ntlworld.com) Subject:Re: De-humidifier question

So, more cost to buy, use more leccy to run.

This is true of all air dryers, of all technologies. As air temp drops the air contains less moisture, so less is extracted.
But since houses stay near to 20C, the change in extraction rate over temp swings is not particularly relevant.

never known that yet, though admittedly I'm not a prolific purchaser of dehumidifiers.

true of any dehumidifier system.

Simpler than a basic microwave in fact. Why do mfrs introduce new tech products? Is it because they believe their own marketing blurb? No, its to make higher profit.
Large industrial sized compressors are expensive, large desiccant wheels are not.

no, they take more power.

No form of air drying is free, compressor dehumidifiers are the cheapest option I've found yet. Fans cost less to buy and install, but chuck a lot of heat out, and are very much less effective than a proper dehumidifier. A lock that allows a window to be secured ajar is the cheapest in the short term, but of course wastes heat just like a fan.
The ideal is to solve the source of the dampness, and do it in a no run cost way. Often this is achievable, but not in all cases. 5 showers a day means a dehumidifier. Or, if you live alone, a sanity check :)
NT
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Oh I just wish our cellar/pantry did, even in summer. It is buried into the side of a wet hill and is permanently cold and damp so we've blocked it off and left unused for now. But would like to at least keep the damp there under some sort of control.
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Mike:

you cant ventilate it at all? WOuld help a lot if you could.
NT
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the
off
Oh continually. Must have several air changes a day though the wall fan we put in but that's why it's so cold in there :-(
You can see water actually trickling in though the wall on bad days so it's isn't really damp, more like running water :-) It used to be the local abattoir so I assume the cold was useful back then. The hooks for hanging carcases are still in the ceiling with a drain in the middle of the room indirectly feeding into the water supply to the local village.
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Fwom:Mike ( snipped-for-privacy@bt.com)

buried into the

blocked it off

there
fan we

so it's

local
hanging
room
Oh I see :( If its that bad I'd be wanting to check the floor joists above for rot, and I'd get one of the bigger model dehumidifiers that can extract more per day. Their quoted extraction rates are, predictably, under somewhat unrealistic optimistic conditions. IMlimitedE the real world extraction rates arent even vaguely comparable to the claims.
Sounds like a better approach would be to dig down beside the house outside and put a barrier in, but that doesnt come cheap, and would need a struc eng to check on how it could be done. Money tends to rule of course.
Have you spoken with the period property people? I'm wondering if gravel plus drain might even do you some good - impossible to know without enough details though. It almost sounds as if your cellar is below the water table!
Or maybe you could just plug the drain and have an indoor swimming pool? :)
NT
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Did that a while back. They were rotten :-(
Currently the end of the house is an open two storey unused space. Need to preserve it whilst we get the rest of the house restored, then thinking of building a two storey self contained metal structure (including stairs, etc) within this space so that damp can be drained away around the outside.

We tried one of the compressor ones a while back and took it back as it did nothing. We now understand this was because the lowest working temperature of these appears to be higher than this area reaches on the hottest summer day. The ones mentioned earlier in this post claim to work down to 5 deg C which is more realistic.

And the local council might have something to say about me removing one of their unnumbered roads

Had a long conversation with some of the real experts on there two years ago (Chris Turner, GreenMan, etc) and have been working through them since then.

That's what Chris suggested and has been done where HM's highway doesn't get in the way. Definitely helped but you wouldn't believe how bad it was when we started. At least it no longer smells damp.

My whole house is below the water table !! We are on the side of a typical Peak District hill - i.e. saturated. Currently our field has standing water on it everywhere. The sheep are asking for wellington boots :-)
Thanks
Mike
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Fwom:Mike ( snipped-for-privacy@bt.com) Subject:Re: De-humidifier question

buried into the

blocked it off

damp there

wall fan we

days so it's

local
hanging
the room

joists
Yeah, not surprised. :/

Need to

thinking of

stairs, etc)

outside.
Metal doesnt like damp at all. Concrete would be much cheaper and tolerates damp. Why metal?

it did

temperature
summer
deg C

Compressor models will work down close to freezing point, as long as they have a defrost on timer function. If they lack that, the cold element will freeze solid at low working temps, and stop working. I suspect that may be the problem. Or else possibly it froze up so quickly that the daily defrost cycle just wasnt adequate - boosting airflow rate would fix that, with a big fat external fan stuck on the air intake. Looking at the cooling coil after its been running a bit will tell you: if its icing, increase the airflow some more.
The extract rate will fall with falling temp for all types, inevitably, as the air just doesnt hold much moisture at low temps.
BTW lime makes a workable desiccant, so you could test the rotor technology with a box a fan and a bag of lime, see what sort of extraction you get.

rule
one of

Fussy buggers arent they?
It might be possible to do it by removing a brick, scraping a space out on the other side 18" wide, or however much you can, filling space with gravel, and replacing said brick. And repeating all over the wall. And while youre doing it, you might be able to paint the other side of the wall with something tarry - not perfectly, but enough to make a huge difference.
Inserting concrete in there would also help, on the other side of the wall, 3:1 crete is pretty much impervious.

years ago

since then.

doesn't get

was when

typical
standing water

Ha. Well, have you installed weep holes? Weep holes would desaturate the ground on the other side of the wall to some extent. Since you dont really want the water running in, drill weep hole and epoxy pipe into it, run pipes to drainage.
Sounds like youve got a very difficult case there.
I'm guessing also youve not replaced the wall mortar? In an old house the lime will all be thoroughly porous, in a powdery state by now. Cutting it out and getting 3:1 cement in there would fix that. As you'll know from the PP folk this would not usually be considered the right thing to do, but in this case it sounds like just whats needed. Why 3:1? Waterproof. The downside is the potential for brick cracking if the house should move/subside, but it sounds like a good risk swap in this case.
I imagnie a 4" interior concrete block wall would be the way to go, tied to the existing wall, after thorough approaches to reducing damp/wet. Using SS ties of course.
One thought does occur: I just wonder if ventilation could possibly be making things worse, if the cellar is colder than outdoor temp, venting will result in condensation and make it wetter. Venting only helps if indoor temp > outdoor.
I really hope this house was very very cheap, cos it sounds a badun.
NT
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Plastic coated metal is impervious to damp and gives a seperate structure just sitting on 6 to 8 struts in the ground Concrete would need major foundations and have to attach to the existing building everywhere which is I expert where damp will collect and may damage what is left.

Unfortunately it's a random stone wall 2 feet thick :-)

This is what the previous owner tried at the side of the house. I can't say it has or hasn't worked as I don't know how bad it was before, but the wall is still damp. In fact you can see the line where the concrete stops (even through 2' of stone) as the wall suddenly gets drier.

boots :-)

This sounds interesting. I assume this is into the uphill side of the hill. Any more details or links ?

Varies. The house had a lime render until 1999 and this kept the mortar in fairly good shape. I have repointed in lime where needed though and am currently playing with lime renders to find the optimum one that will stick in the gales we get here. Unfortunately what you end up needing with is a sacrificial top layer over a base coat. By the time the top layer fails the base coat is absolutely solid. Must be an easier way though.

It's a random stone house and moves regularly :-) There are some concrete repairs and these have sometimes called stone cracking so I'm trying to get rid of it slowly.

That's a good point. Which seems to suggest I should only vent at night. That doesn't sound right but could be.

Nope. But most of house is coming on fine. It has various bits from 1700s to 1980s and is huge. The part we are discussing here is the oldest part right down one end and even if I just sealed it off for good we probably wouldn't miss it. Once complete the gain in value round here will have made it well worth doing. Of course it would have been far easier/cheaper to demolish and start again but Peak Park Authority won't allow that.
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